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  • Other Sources  (86)
  • CITATION GEO-LEO  (86)
  • John Wiley & Sons, Ltd.  (55)
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  • Blackwell Publishing Ltd
  • 1
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    Spatiotemporal variability of the potential wind erosion risk in Southern Africa between 2005 and 2019 (2023)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2023-07-21
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Regional assessments of the wind erosion risk are rare and vary due to the methods used and the available data to be included. The adaptation of existing methods has the advantage that the results can be compared directly. We adopted an already successfully applied methodology (ILSWE—applied in East Africa), to investigate the spatiotemporal variability of the wind erosion risk between 2005 and 2019 in Southern Africa. The approach integrates climatic variables, a vegetation index, and soil properties to describe the potential impact of wind erosion at the landscape scale. The annual and seasonal variability is determined by the vegetation cover, whereas droughts and strong El Niño events had only regional effects. We estimated that 8.3% of the study area experiences a moderate to elevated wind erosion risk over the 15‐year period with annual and inter‐annual fluctuations showing a slight upward trend. In general, the desert and drylands in the west have the highest proportion of risk areas, the moist forests in the east are characterized by a very low risk of wind erosion, while the grasslands, shrublands, and croplands in the interior most likely react to changes of climatic conditions. The validation process is based on a comparison with the estimated frequency of dust storms derived from the aerosol optical depth and angstrom exponent and revealed an overall accuracy of 65%. The results of this study identify regions and yearly periods prone to wind erosion to prioritize for further analysis and conservation policies for mitigation and adaptation strategies.〈/p〉
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: German Federal Ministry of Education and Research (BMBF)
    Description: http://www.climatologylab.org/terraclimate
    Description: https://www.isric.org/
    Description: http://www.fao.org/soils-portal/data-hub/soil-maps-and-databases/harmonized-world-soil-database-v12
    Description: https://land.copernicus.eu/global/products/fcover
    Description: https://www.esa-landcover-cci.org/%20
    Description: https://databasin.org/
    Description: https://giovanni.gsfc.nasa.gov/giovanni/
    Keywords: ddc:551.3 ; environmental modelling ; geographic information systems ; ILSWE model ; remote sensing ; temporal variability ; wind erosion
    Language: English
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  • 2
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    Large‐eddy simulation of soil moisture heterogeneity‐induced secondary circulation with ambient winds (2023)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-03-05
    Description: Land surface heterogeneity in conjunction with ambient winds influences the convective atmospheric boundary layer by affecting the distribution of incoming solar radiation and forming secondary circulations. This study performed coupled large‐eddy simulation (ICON‐LEM) with a land surface model (TERRA‐ML) over a flat river corridor mimicked by soil moisture heterogeneity to investigate the impact of ambient winds on secondary circulations. The coupled model employed double‐periodic boundary conditions with a spatial scale of 4.8 km. All simulations used the same idealized initial atmospheric conditions with constant incident radiation of 700 W⋅m〈sup〉−2〈/sup〉 and various ambient winds with different speeds (0 to 16 m⋅s〈sup〉−1〈/sup〉) and directions (e.g., cross‐river, parallel‐river, and mixed). The atmospheric states are decomposed into ensemble‐averaged, mesoscale, and turbulence. The results show that the secondary circulation structure persists under the parallel‐river wind conditions independently of the wind speed but is destroyed when the cross‐river wind is stronger than 2 m⋅s〈sup〉−1〈/sup〉. The soil moisture and wind speed determine the influence on the surface energy distribution independent of the wind direction. However, secondary circulations increase advection and dispersive heat flux while decreasing turbulent energy flux. The vertical profiles of the wind variance reflect the secondary circulation, and the maximum value of the mesoscale vertical wind variance indicates the secondary circulation strength. The secondary circulation strength positively scales with the Bowen ratio, stability parameter (−Z〈sub〉i〈/sub〉/L), and thermal heterogeneity parameter under cross‐river wind and mixed wind conditions. The proposed similarity analyses and scaling approach provide a new quantitative perspective on the impact of the ambient wind under heteronomous soil moisture conditions on secondary circulation.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.5 ; ambient winds ; Bowen ratio ; land surface model ; large‐eddy simulation ; moisture spatial heterogeneity ; secondary circulation ; similarity theory ; turbulence
    Language: English
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  • 3
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    Added value of an atmospheric circulation pattern‐based statistical downscaling approach for daily precipitation distributions in complex terrain (2023)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-01-24
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Reliable prediction of heavy precipitation events causing floods in a world of changing climate is crucial for the development of appropriate adaption strategies. Many attempts to provide such predictions have already been conducted but there is still much potential for improvement left. This is particularly true for statistical downscaling of heavy precipitation due to changes present in the corresponding atmospheric drivers. In this study, a circulation pattern (CP) conditional downscaling to the station level is proposed which considers occurring frequency changes of CPs. Following a strict circulation‐to‐environment approach we use atmospheric predictors to derive CPs. Subsequently, precipitation observations are used to derive CP conditional cumulative distribution functions (CDFs) of daily precipitation. Raw precipitation time series are sampled from these CDFs. Bias correction is applied to the sampled time series with quantile mapping (QM) and parametric transfer functions (PTFs) as methods being tested. The added value of this CP conditional downscaling approach is evaluated against the corresponding common non‐CP conditional approach. The performance evaluation is conducted by using Kling–Gupta Efficiency (KGE), root mean squared error (RMSE), and mean absolute error (MAE) metrics. In both cases the applied bias correction is identical. Potential added value can therefore only be attributed to the CP conditioning. It can be shown that the proposed CP conditional downscaling approach is capable of yielding more reliable and accurate downscaled daily precipitation time series in comparison to a non‐CP conditional approach. This can be seen in particular for the extreme parts of the distribution. Above the 95th percentile, an average performance gain of +0.24 and a maximum gain of +0.6 in terms of KGE is observed. These findings support the assumption of conserving and utilizing atmospheric information through CPs can be beneficial for more reliable statistical precipitation downscaling. Due to the availability of these atmospheric predictors in climate model output, the presented method is potentially suitable for downscaling precipitation projections.〈/p〉
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-pressure-levels?tab=overview
    Description: https://cdc.dwd.de/portal/
    Keywords: ddc:551.5 ; bias correction ; circulation patterns ; ERA5 ; extreme events ; heavy precipitation ; simulated annealing ; statistical downscaling
    Language: English
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  • 4
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    Toward an adequate level of detail in flood risk assessments (2023)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2024-01-24
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Flood risk assessments require different disciplines to understand and model the underlying components hazard, exposure, and vulnerability. Many methods and data sets have been refined considerably to cover more details of spatial, temporal, or process information. We compile case studies indicating that refined methods and data have a considerable effect on the overall assessment of flood risk. But are these improvements worth the effort? The adequate level of detail is typically unknown and prioritization of improvements in a specific component is hampered by the lack of an overarching view on flood risk. Consequently, creating the dilemma of potentially being too greedy or too wasteful with the resources available for a risk assessment. A “sweet spot” between those two would use methods and data sets that cover all relevant known processes without using resources inefficiently. We provide three key questions as a qualitative guidance toward this “sweet spot.” For quantitative decision support, more overarching case studies in various contexts are needed to reveal the sensitivity of the overall flood risk to individual components. This could also support the anticipation of unforeseen events like the flood event in Germany and Belgium in 2021 and increase the reliability of flood risk assessments.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: BMBF http://dx.doi.org/10.13039/501100002347
    Description: Federal Environment Agency http://dx.doi.org/10.13039/501100010809
    Description: http://howas21.gfz-potsdam.de/howas21/
    Description: https://www.umwelt.niedersachsen.de/startseite/themen/wasser/hochwasser_amp_kustenschutz/hochwasserrisikomanagement_richtlinie/hochwassergefahren_und_hochwasserrisikokarten/hochwasserkarten-121920.html
    Description: https://download.geofabrik.de/europe/germany.html
    Description: https://emergency.copernicus.eu/mapping/list-of-components/EMSN024
    Description: https://data.jrc.ec.europa.eu/collection/id-0054
    Description: https://oasishub.co/dataset/surface-water-flooding-footprinthurricane-harvey-august-2017-jba
    Description: https://www.wasser.sachsen.de/hochwassergefahrenkarte-11915.html
    Keywords: ddc:551.48 ; decision support ; extreme events ; integrated flood risk management ; risk assessment
    Language: English
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  • 5
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    Small lateral air pressure gradients generated by a large chamber system have a strong effect on CO2 transport in soil (2023)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2024-02-09
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Gas transport in soils is usually assumed to be purely diffusive, although several studies have shown that non‐diffusive processes can significantly enhance soil gas transport. These processes include barometric air pressure changes, wind‐induced pressure pumping and static air pressure fields generated by wind interacting with obstacles. The associated pressure gradients in the soil can cause advective gas fluxes that are much larger than diffusive fluxes. However, the contributions of the respective transport processes are difficult to separate. We developed a large chamber system to simulate pressure fields and investigate their influence on soil gas transport. The chamber consists of four subspaces in which pressure is regulated by fans that blow air in or out of the chamber. With this setup, we conducted experiments with oscillating and static pressure fields. CO〈sub〉2〈/sub〉 concentrations were measured along two soil profiles beneath the chamber. We found a significant relationship between static lateral pressure gradients and the change in the CO〈sub〉2〈/sub〉 profiles (R〈sup〉2〈/sup〉 = 0.53; 〈italic toggle="no"〉p〈/italic〉‐value 〈2e‐16). Even small pressure gradients between −1 and 1 Pa relative to ambient pressure resulted in an increase or decrease in CO〈sub〉2〈/sub〉 concentrations of 8% on average in the upper soil, indicating advective flow of air in the pore space. Positive pressure gradients resulted in decreasing, negative pressure gradients in increasing CO〈sub〉2〈/sub〉 concentrations. The concentration changes were probably caused by an advective flow field in the soil beneath the chamber generated by the pressure gradients. No effect of oscillating pressure fields was observed in this study. The results indicate that static lateral pressure gradients have a substantial impact on soil gas transport and therefore are an important driver of gas exchange between soil and atmosphere. Lateral pressure gradients in a comparable range can be induced under windy conditions when wind interacts with terrain features. They can also be caused by chambers used for flux measurements at high wind speed or by fans used for head‐space mixing within the chambers, which yields biased flux estimates.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:631.4 ; advective flux ; chamber flux measurements ; static air pressure fields ; wind‐induced pressure pumping
    Language: English
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  • 6
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    East Asian summer precipitation in AWI‐CM3: Comparison with observations and CMIP6 models (2023)
    John Wiley & Sons, Ltd. | Chichester, UK
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    Publication Date: 2023-11-13
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Owing to the complicated spatial–temporal characteristics of East Asian precipitation (EAP), climate models have limited skills in simulating the modern Asian climate. This consequently leads to large uncertainties in simulations of the past EAP variation and future projections. Here, we explore the performance of the newly developed Alfred Wegener Institute Climate Model, version 3 (AWI‐CM3) in simulating the climatological summer EAP. To test whether the model's skill depends on its atmosphere resolution, we design two AWI‐CM3 simulations with different horizontal resolutions. The result shows that both simulations have acceptable performance in simulating the summer mean EAP, generally better than the majority of individual models participating in the Coupled Model Intercomparison Project (CMIP6). However, for the monthly EAP from June to August, AWI‐CM3 exhibits a decayed skill, which is due to the subseasonal movement of the western Pacific subtropical high bias. The higher‐resolution AWI‐CM3 simulation shows an overall improvement relative to the one performed at a relatively lower resolution in all aspects taken into account regarding the EAP. We conclude that AWI‐CM3 is a suitable tool for exploring the EAP for the observational period. Having verified the model's skill for modern climate, we suggest employing the AWI‐CM3, especially with high atmosphere resolution, both for applications in paleoclimate studies and future projections.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉This figure shows the skill scores of AWI‐CM3 and CMIP6 models in simulating the climatological summer East Asian precipitation (EAP), which indicates that AWI‐CM3 simulations perform better than most CMIP6 individual models for the summer mean EAP, while AWI‐CM3's skills decay from June to August.〈boxed-text position="anchor" content-type="graphic" id="joc8075-blkfxd-0001" xml:lang="en"〉 〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:08998418:media:joc8075:joc8075-toc-0001"〉 〈alt-text〉image〈/alt-text〉 〈/graphic〉 〈/boxed-text〉〈/p〉
    Description: National Natural Science Foundation of China http://dx.doi.org/10.13039/501100001809
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Helmholtz Climate Initiative REKLIM
    Description: Helmholtz Program
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: China Scholarship Council http://dx.doi.org/10.13039/501100004543
    Description: https://opendata.dwd.de/climate_environment/GPCC/html/fulldata-monthly_v2022_doi_download.html
    Description: https://crudata.uea.ac.uk/cru/data/hrg/cru_ts_4.05
    Description: http://aphrodite.st.hirosaki-u.ac.jp/products.html
    Description: https://jra.kishou.go.jp/JRA-55/index_en.html
    Description: https://esgf-node.llnl.gov/search/cmip6
    Keywords: ddc:551.6 ; AWI‐CM3 ; CMIP6 ; East Asia ; summer precipitation
    Language: English
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  • 7
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    Redoxtrons – An experimental system to study redox processes within the capillary fringe (2023)
    Blackwell Publishing Ltd | Oxford, UK
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    Publication Date: 2023-11-18
    Description: Spatiotemporal characterisation of the soil redox status within the capillary fringe (CF) is a challenging task. Air‐filled porosities (ε), oxygen concentration (O〈sub〉2〈/sub〉) and soil redox potential (EH) are interrelated soil variables within active biogeochemical domains such as the CF. We investigated the impact of water table (WT) rise and drainage in an undisturbed topsoil and subsoil sample taken from a Calcaric Gleysol for a period of 46 days. We merged 1D (EH and matric potential) and 2D (O〈sub〉2〈/sub〉) systems to monitor at high spatiotemporal resolution redox dynamics within self‐constructed redoxtron housings and complemented the data set by a 3D pore network characterization using X‐ray microtomography (X‐ray μCT). Depletion of O〈sub〉2〈/sub〉 was faster in the organic matter‐ and clay‐rich aggregated topsoil and the CF extended 〉10 cm above the artificial WT. The homogeneous and less‐aggregated subsoil extended only 4 cm above the WT as indicated by ε–O〈sub〉2〈/sub〉–EH data during saturation. After drainage, 2D O〈sub〉2〈/sub〉 imaging revealed a fast aeration towards the lower depths of the topsoil, which agrees with the connected ε derived by X‐ray μCT (ε〈sub〉CT_conn〈/sub〉) of 14.9% of the total porosity. However, small‐scaled anoxic domains with O〈sub〉2〈/sub〉 saturation 〈5% were apparent even after lowering the WT (down to 0.25 cm〈sup〉2〈/sup〉 in size) for 23 days. These domains remained a nucleus for reducing soil conditions (E〈sub〉H〈/sub〉 〈 −100 mV), which made it challenging to characterise the soil redox status in the CF. In contrast, the subsoil aeration reached O〈sub〉2〈/sub〉 saturation after 8 days for the complete soil volume. Values of ε〈sub〉CT_conn〈/sub〉 around zero in the subsoil highlighted that soil aeration was independent of this parameter suggesting that other variables such as microbial activity must be considered when predicting the soil redox status from ε alone. The use of redoxtrons in combination with localised redox‐measurements and image based pore space analysis resulted in a better 2D/3D characterisation of the pore system and related O〈sub〉2〈/sub〉 transport properties. This allowed us to analyse the distribution and activity of microbiological niches highly associated with the spatiotemporal variable redox dynamics in soil environments. Highlights: The time needed to turn from reducing to oxidising (period where all platinum electrodes feature E〈sub〉H〈/sub〉 〉 300 mV) condition differ for two samples with contrasting soil structure. The subsoil with presumably low O〈sub〉2〈/sub〉 consumption rates aerated considerably faster than the topsoil and exclusively by O〈sub〉2〈/sub〉 diffusion through medium‐ and fine‐sized pores. To derive the soil redox status based upon the triplet ε–O〈sub〉2〈/sub〉–E〈sub〉H〈/sub〉 is challenging at present in heterogeneous soil domains and larger soil volumes than 250 cm〈sup〉3〈/sup〉. Undisturbed soil sampling along with 2D/3D redox measurement systems (e.g., redoxtrons) improve our understanding of redox dynamics within the capillary fringe.
    Keywords: ddc:631.4 ; environmental monitoring ; incubation experiments ; redox processes ; soil reducing conditions ; undisturbed soil ; X‐ray microtomography
    Language: English
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  • 8
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    The dilemma of analytical method changes for soil organic carbon in long‐term experiments (2023)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2023-11-17
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈sec xmlns:mml="http://www.w3.org/1998/Math/MathML" id="ejss13362-sec-1003" xml:lang="en"〉 〈p xml:lang="en"〉Long‐term experiments (LTEs) have provided data to modellers and agronomists to investigate changes and dynamics of soil organic carbon (SOC) under different cropping systems. As treatment changes have occurred due to agricultural advancements, so too have analytical soil methods. This may lead to method bias over time, which could affect the robust interpretation of data and conclusions drawn. This study aims to quantify differences in SOC due to changes in dry combustion methods over time, using soil samples of a LTE established in 1963 that focuses on mineral and organic fertilizer management in the temperate zone of Northeast Germany. For this purpose, 1059 soil samples, collected between 1976 and 2008, have been analysed twice, once with their historical laboratory method right after sampling, and a second time in 2016 when all samples were analysed using the same elementary analyser. In 9 of 11 soil sampling campaigns, a paired 〈italic toggle="no"〉t〈/italic〉‐test provided evidence for significant differences in the historical SOC values when compared with the re‐analysed concentrations of the same LTE sample. In the sampling years 1988 and 2004, the historical analysis obtained about 0.9 g kg〈sup〉−1〈/sup〉 lower SOC compared with the re‐analysed one. For 1990 and 1998, this difference was about 0.4 g kg〈sup〉−1〈/sup〉. Correction factors, an approach often used to correct for different analytical techniques, could only be applied for 5 of 11 sampling campaigns to account for constant and proportional systematic method error. For this particular LTE, the interpretation of SOC changes due to agronomic management (here fertilization) deviates depending on the analytical method used, which may weaken the explanatory power of the historical data. We demonstrate that analytical method changes over time present one of many challenges in the interpretation of time series data of SOC dynamics. Therefore, LTE site managers need to ensure providing all necessary protocols and data in order to retrace method changes and if necessary recalculate SOC.〈/p〉 〈/sec〉〈sec xmlns:mml="http://www.w3.org/1998/Math/MathML" id="ejss13362-sec-0003" xml:lang="en"〉 〈title〉Highlights〈/title〉 〈p xml:lang="en"〉〈list list-type="bullet" id="ejss13362-list-0001"〉 〈list-item id="ejss13362-li-0001"〉〈p〉A total of 1059 LTE soil samples taken between 1976 and 2008 were re‐analysed for SOC in 2016〈/p〉〈/list-item〉 〈list-item id="ejss13362-li-0002"〉〈p〉Several methodological changes for SOC determination led to significant different SOC concentration in the same sample〈/p〉〈/list-item〉 〈list-item id="ejss13362-li-0003"〉〈p〉Interpretation and time series of LTE soil data suffer from consideration of analytical method changes and poor documentation of the same〈/p〉〈/list-item〉 〈list-item id="ejss13362-li-0004"〉〈p〉Soil archive establishment, thorough method protocols and diligent proficiency testing after soil method changes ameliorate the dilemma〈/p〉〈/list-item〉 〈/list〉〈/p〉 〈/sec〉
    Description: Brandenburger Staatsministerium für Wissenschaft, Forschung und Kultur http://dx.doi.org/10.13039/501100004581
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100004937
    Description: https://doi.org/10.4228/zalf-acge-b683
    Keywords: ddc:631.4 ; Bland–Altman ; carbon stocks ; data trueness ; Deming regression ; method bias ; soil archive ; soil survey
    Language: English
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  • 9
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    Optimised use of data fusion and memory‐based learning with an Austrian soil library for predictions with infrared data (2023)
    Blackwell Publishing Ltd | Oxford, UK
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    Publication Date: 2023-12-12
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Infrared spectroscopy in the visible to near‐infrared (vis–NIR) and mid‐infrared (MIR) regions is a well‐established approach for the prediction of soil properties. Different data fusion and training approaches exist, and the optimal procedures are yet undefined and may depend on the heterogeneity present in the set and on the considered scale. The objectives were to test the usefulness of partial least squares regressions (PLSRs) for soil organic carbon (SOC), total carbon (C〈sub〉t〈/sub〉), total nitrogen (N〈sub〉t〈/sub〉) and pH using vis–NIR and MIR spectroscopy for an independent validation after standard calibration (use of a general PLSR model) or using memory‐based learning (MBL) with and without spiking for a national spectral database. Data fusion approaches were simple concatenation of spectra, outer product analysis (OPA) and model averaging. In total, 481 soils from an Austrian forest soil archive were measured in the vis–NIR and MIR regions, and regressions were calculated. Fivefold calibration‐validation approaches were carried out with a region‐related split of spectra to implement independent validations with n ranging from 47 to 99 soils in different folds. MIR predictions were generally superior over vis–NIR predictions. For all properties, optimal predictions were obtained with data fusion, with OPA and spectra concatenation outperforming model averaging. The greatest robustness of performance was found for OPA and MBL with spiking with 〈italic toggle="no"〉R〈/italic〉〈sup〉2〈/sup〉 ≥ 0.77 (N), 0.85 (SOC), 0.86 (pH) and 0.88 (C〈sub〉t〈/sub〉) in the validations of all folds. Overall, the results indicate that the combination of OPA for vis–NIR and MIR spectra with MBL and spiking has a high potential to accurately estimate properties when using large‐scale soil spectral libraries as reference data. However, the reduction of cost‐effectiveness using two spectrometers needs to be weighed against the potential increase in accuracy compared to a single MIR spectroscopy approach.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:631.4 ; data fusion ; independent validation ; infrared spectroscopy ; MBL ; nitrogen ; outer product analysis ; pH ; soil organic carbon ; spiking ; total carbon
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  • 10
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    Importance of catchment hydrological processes and calibration of hydrological‐hydrodynamic rainfall‐runoff models in small rural catchments (2023)
    Blackwell Publishing Ltd | Oxford, UK
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    Publication Date: 2024-01-19
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉In recent years, many two‐dimensional (2D) hydrodynamic models have been extended to include the direct rainfall method (DRM). This allows their application as a hydrological‐hydrodynamic model for the determination of floodplains in one model system. In previous studies on DRM, the role of catchment hydrological processes (CaHyPro) and its interaction with the calibration process was not investigated in detail. In the present, case‐oriented study, the influence of the spatiotemporal distribution of the processes precipitation and runoff formation in combination with the 2D model HEC‐RAS is investigated. In a further step, a conceptual approach for event‐based interflow is integrated. The study is performed on the basis of a single storm event in a small rural catchment (low mountain range, 38 km〈sup〉2〈/sup〉) in Hesse (Germany). The model results are evaluated against six quality criteria and compared to a simplified baseline model. Finally, the calibrated improved model is contrasted with a calibrated baseline model. The results show the enhancement of the model results due to the integration of the CaHyPro and highlight its interplay with the calibrated model parameters.〈/p〉
    Keywords: ddc:551.48 ; 2D hydrodynamic modeling ; calibration ; direct rainfall modeling ; hydrological processes ; radar data ; runoff formation
    Language: English
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  • 11
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    BODIUM—A systemic approach to model the dynamics of soil functions (2023)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2024-01-26
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The increasing demand for biomass for food, animal feed, fibre and bioenergy requires optimization of soil productivity, while at the same time, protecting other soil functions such as nutrient cycling and buffering, carbon storage, habitat for biological activity and water filter and storage. Therefore, one of the main challenges for sustainable agriculture is to produce high yields while maintaining all the other soil functions. Mechanistic simulation models are an essential tool to fully understand and predict the complex interactions between physical, biological and chemical processes of soils that generate those functions. We developed a soil model to simulate the impact of various agricultural management options and climate change on soil functions by integrating the relevant processes mechanistically and in a systemic way. As a special feature, we include the dynamics of soil structure induced by tillage and biological activity, which is especially relevant in arable soils. The model operates on a 1D soil profile consisting of a number of discrete layers with dynamic thickness. We demonstrate the model performance by simulating crop growth, root growth, nutrient and water uptake, nitrogen cycling, soil organic matter turnover, microbial activity, water distribution and soil structure dynamics in a long‐term field experiment including different crops and different types and levels of fertilization. The model is able to capture essential features that are measured regularly including crop yield, soil organic carbon, and soil nitrogen. In this way, the plausibility of the implemented processes and their interactions is confirmed. Furthermore, we present the results of explorative simulations comparing scenarios with and without tillage events to analyse the effect of soil structure on soil functions. Since the model is process‐based, we are confident that the model can also be used to predict quantities that have not been measured or to estimate the effect of management measures and climate states not yet been observed. The model thus has the potential to predict the site‐specific impact of management decisions on soil functions, which is of great importance for the development of a sustainable agriculture that is currently also on the agenda of the ‘Green Deal’ at the European level.〈/p〉
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: https://git.ufz.de/bodium/bodium_v1.0
    Keywords: ddc:631.4 ; agriculture ; computational model ; simulation ; soil microbiology ; soil structure ; sustainable soil
    Language: English
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  • 12
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    A multi‐parameter approach to quantify riverbed clogging and vertical hyporheic connectivity (2023)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-01-26
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Riverbed clogging is key to assessing vertical connectivity in the hyporheic zone and is often quantified using single‐parameter or qualitative approaches. However, clogging is driven by multiple, interacting physical and bio‐geochemical parameters, which do not allow for a conclusive assessment of hyporheic connectivity with single‐parameter approaches. In addition, existing qualitative assessments lack transparency and repeatability. This study introduces a Multi‐Parameter Approach to quantify Clogging and vertical hyporheic connectivity (MultiPAC), which builds on standardized measurements of physical (grain size characteristics, porosity, hydraulic conductivity) and bio‐geochemical (interstitial dissolved oxygen) parameters. We apply MultiPAC at three gravel‐bed rivers and show how the set of parameters provides a representative appreciation of physical riverbed clogging, thus quantifying vertical hyporheic connectivity. However, more parameters are required to fully characterize biological clogging. In addition, MultiPAC locates clogged layers in the hyporheic zone through multi‐parameter vertical profiles over the riverbed depth. The discussion outlines the relevance of MultiPAC to guide field surveys.〈/p〉
    Description: https://github.com/Ecohydraulics/kf-converter-w-flopy
    Keywords: ddc:550.724 ; colmation ; dissolved oxygen ; grain size ; hydraulic conductivity ; porosity ; siltation
    Language: English
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  • 13
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    Projected changes in synoptic circulations over Europe and their implications for summer precipitation: A CMIP6 perspective (2023)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-01-30
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Projected changes in summer precipitation deficits partly depend on alterations in synoptic circulations. Here, the automated Jenkinson–Collison classification is used to assess the ability of 21 global climate models (GCMs) to capture the frequency of recurring circulation types (CTs) and their implications for European daily precipitation amounts in summer (JJA). The ability of the GCMs to reproduce the observed present‐day climate features is evaluated first. Most GCMs capture the observed links between the mean CTs directional flow characteristics and the occurrence of dry days and related dry months. The most robust relationships are found for anticyclonic and easterly CTs which are generally associated with higher‐than‐average occurrences of dry conditions. Future changes in summer CTs' frequencies are estimated in the high‐emission SSP5‐8.5 scenario for the sake of a high signal‐to‐noise ratio. Our results reveal consistent changes, mainly in the zonal CTs. A robust decrease in frequency of the westerlies and an increase in the frequency of easterly CTs favour more continental, dry and warm air masses over central Europe. These dynamical changes are shown to enhance the projected summer drying over central and southern Europe.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Summer large‐scale circulations are derived over Europe using an automated classification. Spatial characteristics of the patterns and their influence on dry days are investigated. Future changes are explored based on global climate models. The predicted drier summers in Europe are found to be influenced by consistent changes in west‐easterly circulations.〈boxed-text position="anchor" content-type="graphic" id="joc8033-blkfxd-0001" xml:lang="en"〉 〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:08998418:media:joc8033:joc8033-toc-0001"〉 〈/graphic〉 〈/boxed-text〉〈/p〉
    Description: EU International Training Network (ITN) Climate Advanced Forecasting of sub‐seasonal Extremes (CAFE)
    Description: H2020 Marie Skłodowska‐Curie Actions
    Description: https://github.com/PedroLormendez/jcclass
    Keywords: ddc:551.6 ; circulation patterns ; climate change ; precipitation ; weather extremes
    Language: English
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  • 14
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    Temperature and soil moisture change microbial allocation of pesticide‐derived carbon (2023)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2024-03-18
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Temperature and soil moisture are known to control pesticide mineralization. Half‐life times (DT〈sub〉50〈/sub〉) derived from pesticide mineralization curves generally indicate longer residence times at low soil temperature and moisture but do not consider potential changes in the microbial allocation of pesticide‐derived carbon (C). We aimed to determine carbon use efficiency (CUE, formation of new biomass relative to total C uptake) to better understand microbial utilization of pesticide‐derived C under different environmental conditions and to support the conventional description of degradation dynamics based on mineralization. We performed a microcosm experiment at two MCPA (2‐methyl‐4‐chlorophenoxyacetic acid) concentrations (1 and 20 mg kg〈sup〉−1〈/sup〉) and defined 20°C/pF 1.8 as optimal and 10°C/pF 3.5 as limiting environmental conditions. After 4 weeks, 70% of the initially applied MCPA was mineralized under optimal conditions but MCPA mineralization reached less than 25% under limiting conditions. However, under limiting conditions, an increase in CUE was observed, indicating a shift towards anabolic utilization of MCPA‐derived C. In this case, increased C assimilation implied C storage or the formation of precursor compounds to support resistance mechanisms, rather than actual growth since we did not find an increase in the 〈italic toggle="no"〉tfdA〈/italic〉 gene relevant to MCPA degradation. We were able to confirm the assumption that under limiting conditions, C assimilation increases relative to mineralization and that C redistribution, may serve as an explanation for the difference between mineralization and MCPA dissipation‐derived degradation dynamics. In addition, by introducing CUE to the temperature‐ and moisture‐dependent degradation of pesticides, we can capture the underlying microbial constraints and adaptive mechanisms to changing environmental conditions.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Changing environmental conditions alter the MCPA degradation dynamics and the allocation of pesticide‐derived carbon to anabolic or catabolic metabolism.〈boxed-text position="anchor" content-type="graphic" id="ejss13417-blkfxd-0001" xml:lang="en"〉 〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:13510754:media:ejss13417:ejss13417-toc-0001"〉 〈/graphic〉 〈/boxed-text〉〈/p〉
    Description: Collaborative Research Center 1253 CAMPOS (DFG)
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: DFG Priority Program 2322 “Soil System”
    Description: Ellrichshausen Foundation
    Description: Research Training Group “Integrated Hydrosystem modeling”
    Description: https://doi.org/10.5281/zenodo.5081655
    Keywords: ddc:631.4 ; anabolism ; carbon use efficiency ; catabolism ; effect of soil moisture and temperature ; gene‐centric process model ; MCPA biodegradation
    Language: English
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  • 15
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    Hydrodynamic modeling of ephemeral flow in the Iishana channel systems of the Cuvelai Basin—Northern Namibia (2023)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-04-19
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The transboundary region of the Iishana system in the western Cuvelai Basin, between southern Angola and northern Namibia, is frequently affected by floods at irregular intervals. As a result, the predominantly rural, subsistence farming population has experienced crop failures, human, and economic losses. To date, very little is known about the generation of floods, flood concentration, and stormwater drainage dynamics in this region. In this study, 2D‐hydrodynamic modeling was applied to reconstruct one of the latest major flood events during the rainy season from November 2008 to March 2009 in order to study the runoff behavior and interconnectivity of the Iishana system. The model focused on the eastern part of the Iishana system, which was most affected by floods and flood damage due to the high population density in and around Oshakati, the regional capital. Two main streams were identified noteworthy because they merge and subsequently affect Oshakati. Regarding the simulated flood event water depths vary from 0.1 m to 14 m, with an average of 0.2 m, while water depths above 5 m were attributed to borrow pits. The inundation area ranged up to 1860 km〈sup〉2〈/sup〉 and the amount of water left after the rainy season on March 25th, 2009, was determined between 0.116 and 0.547 km〈sup〉3〈/sup〉, depending on the amount of evapotranspiration considered in the model. Thus, in the Angolan part of the Iishana system, significantly larger quantities of water are available for longer periods of time during the subsequent dry season, whereas the system in Namibia stores less water, resulting in a shorter water retention period.〈/p〉
    Description: Deutsche Hydrologische Gesellschaft (DHG)
    Description: Freie Universität Berlin http://dx.doi.org/10.13039/501100007537
    Description: https://dx.doi.org/10.17169/refubium-35737
    Keywords: ddc:551.48 ; flood ; FloodArea11 ; SCS‐CN ; TanDEM‐X ; TRMM
    Language: English
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  • 16
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    Radar‐based heavy precipitation events in Germany and associated circulation patterns (2023)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-05-22
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉As projected by multiple climate models, short‐duration heavy precipitation events (SDHPEs) are expected to intensify particularly quickly under the changing climate posing substantial risk to natural and human systems. Yet over the years, SDHPEs have received less scientific attention than long‐duration heavy precipitation events (LDHPEs), mainly due to the limitations of measurement systems. Our aim is to provide insight into spatial and temporal variability of SDHPEs detected by the radar network of the 〈italic toggle="no"〉Deutscher Wetterdienst〈/italic〉 (DWD) in Germany from 2001 to 2020 as well as to explore their links to circulation patterns (CPs). The study is based on the Catalogue of Radar‐based heavy Rainfall Events (CatRaRE) generated using reprocessed gauge‐adjusted data of the DWD radar network as well as a new numerical method for classifying CPs over Central Europe called “〈italic toggle="no"〉Großwetterlagen〈/italic〉 for Reanalyses” (GWL‐REA). The results have demonstrated that SDHPEs, which are defined based on either locally valid precipitation values with a return period of 5 years (CatRaRE T5) or absolute precipitation values equal to DWD Warning Level 3 (CatRaRE W3), are common phenomena occurring most frequently in the afternoon hours of the summer season. They constitute up to 90% of all heavy precipitation events included in the catalogues covering relatively small areas—the median area of SDHPEs ranges from 22 km〈sup〉2〈/sup〉 (CatRaRE T5) to 24 km〈sup〉2〈/sup〉 (CatRaRE W3), while the median area of LDHPEs ranges from 175 km〈sup〉2〈/sup〉 (CatRaRE W3) to 184 km〈sup〉2〈/sup〉 (CatRaRE T5). As compared to LDHPEs, SDHPEs are generated by a wider spectrum of circulation conditions, including not only cyclonic but also anticyclonic CPs. In the warm season, the anticyclonic CPs, often accompanied by air mass advection from the south, can induce high thermal instability leading to the development of relatively small, isolated convective cells, which often cannot be captured by rain gauge stations.〈/p〉
    Description: Federal Ministry for Digital and Transport (BMDV)
    Description: https://www.dwd.de/DE/leistungen/catrare/catrare.html
    Keywords: ddc:551.6 ; CatRaRE ; circulation patterns ; GWL‐REA ; heavy precipitation events ; long‐duration precipitation ; radar data ; short‐duration precipitation
    Language: English
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    Fifty years after deep‐ploughing: Effects on yield, roots, nutrient stocks and soil structure (2023)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2024-05-30
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Deep‐ploughing far beyond the common depth of 30 cm was used more than 50 years ago in Northern Germany with the aim to break root‐restricting layers and thereby improve access to subsoil water and nutrient resources. We hypothesized that effects of this earlier intervention on soil properties and yields prevailed after 50 years. Hence, we sampled two sandy soils and one silty soil (Cambisols and a Luvisol) of which half of the field had been deep‐ploughed 50 years ago (soils then re‐classified as Treposols). The adjacent other half was not deep‐ploughed and thus served as the control. At all the three sites, both deep‐ploughed and control parts were then conventionally managed over the last 50 years. We assessed yields during the dry year 2019 and additionally in 2020, and rooting intensity at the year of sampling (2019), as well as changes in soil structure, carbon and nutrient stocks in that year. We found that deep‐ploughing improved yields in the dry spell of 2019 at the sandy sites, which was supported by a more general pattern of higher NDVI indices in deep‐ploughed parts for the period from 2016 to 2021 across varying weather conditions. Subsoil stocks of soil organic carbon and total plant‐available phosphorus were enhanced by 21%–199% in the different sites. Root biomass in the subsoil was reduced due to deep‐ploughing at the silty site and was increased or unaffected at the sandy sites. Overall, the effects of deep‐ploughing were site‐specific, with reduced bulk density in the buried topsoil stripes in the subsoil of the sandy sites, but with elevated subsoil density in the silty site. Hence, even 50 years after deep‐ploughing, changes in soil properties are still detectable, although effect size differed among sites.〈/p〉
    Description: BonaRes http://dx.doi.org/10.13039/501100022576
    Keywords: ddc:631.4 ; aggregates ; carbon sequestration ; deep‐ploughing ; macronutrients ; subsoil ; Treposol
    Language: English
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    Feasibility of pXRF to evaluate chosen heavy metals in soil highly influenced by municipal waste disposal—A monitoring study of a former sewage farm (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-04-04
    Description: Sewage disposal onto agricultural land may result in the high accumulation of organic wastes, which questions the applicability of typical elemental analysis used for the soil components. To monitor the contamination status of agricultural soils at a former sedimentation basin, after the long‐term cessation of wastewater irrigation, 110 locations (15–20 cm depth) and 4 boreholes (up to 100 cm depth) were sampled to determine pH, loss on ignition, and concentration of Ni, Cu, Pb, Zn, and Cr. Additionally, the applicability of portable X‐ray fluorescence (pXRF) for the soil samples highly influenced by the organic wastes was evaluated. The study revealed the presence of a relatively homogenous sewage waste layer (depth of 20 cm), characterized by slightly acidic to neutral pH (6.3–7.5), high organic matter (OM) accumulation (up to 49%), and elevated concentration (mg kg −1) ranges between: Pb (5–321), Cu (31–2828), Ni (10–193), Cr (14–966), and Zn (76–6639). The pXRF analysis revealed metal concentration increase in mineral samples (up to 50%). The regression models and correction factors demonstrated high correlation and significance of pXRF measurement with response to increasing OM content, with the lowest r 2 = 0.86 obtained for Ni. Correlation of pXRF and AES measurement illustrated element‐dependent response for soils high in organics. Zn, Cu, and Cr pXRF analysis led to a slight underestimation in lower values, but overall good correlations (0.87; 0.89; and 0.88 respectively). Pb and Ni pXRF measurement revealed higher deviation from the reference in both lower and higher concentrations (0.74 and 0.70, respectively).
    Description: German Federation of Industrial Research Associations http://dx.doi.org/10.13039/501100002723
    Description: Federal Ministry for Economic Affairs and Energy http://dx.doi.org/10.13039/501100006360
    Keywords: ddc:577.14
    Language: English
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    Spatio‐temporal patterns in degradation and restoration of gravel bars along Alpine rivers (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-06-28
    Description: Braided reaches were common along near‐natural Alpine rivers, and the associated habitat dynamics supported plant and animal species specialized on early‐successional stages. The extensive riparian zones could mitigate climate change by absorbing floods and by retaining water during droughts. Human impacts largely reduced active river corridors through altered discharge and construction of dykes, while recent restoration projects aim at increasing river dynamics. The causes and consequences of Alpine river degradation are well understood, but there are only few quantitative studies on floodplain degradation and restoration. Thus, we have reconstructed historical changes of gravel bars along five Alpine rivers (Iller, Inn, Isar, Lech, and Wertach) in Southern Germany in the period 1808–2009, based on historical maps and aerial images. We found losses of 〉90% in gravel bar area along these rivers since the mid‐19th century. The decline was caused by a reduction of the active river corridor and by ongoing succession of the remaining open habitats. Within the past 30 years, at the Isar River, restoration measures were realized with the aim to widen the active river corridor and to recreate gravel bars. In four restored reaches, we found that 5% of the historical gravel bar area recovered, and that the proportion of restored gravel bar area was highest after intermediate flooding. We conclude that the active river corridors of German Alpine rivers are almost completely lost, and that more extensive restoration needs to be done to preserve the habitat dynamics and biodiversity of these systems, and to adapt Alpine rivers to climate change.
    Description: Deutsche Bundesstiftung Umwelt http://dx.doi.org/10.13039/100007636
    Keywords: ddc:551.35
    Language: English
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    Comparing the performance of high‐resolution global precipitation products across topographic and climatic gradients of Central Asia (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-10-13
    Description: Accurate and reliable precipitation data with high spatial and temporal resolution are essential in studying climate variability, water resources management, and hydrological forecasting. A range of global precipitation data are available to this end, but how well these capture actual precipitation remains unknown, particularly for mountain regions where ground stations are sparse. We examined the performance of three global high‐resolution precipitation products for capturing precipitation over Central Asia, a hotspot of climate change, where reliable precipitation data are particularly scarce. Specifically, we evaluated MSWEP, CHIRPS, and GSMAP against independent gauging stations for the period 1985–2015. Our results show that MSWEP and CHIRPS outperformed GSMAP for wetter periods (i.e., winter and spring) and wetter locations (150–600 mm·year−1), lowlands, and mid‐altitudes (0–3,000 m), and regions dominated by winter and spring precipitation. MSWEP performed best in representing temporal precipitation dynamics and CHIRPS excelled in capturing the volume and distribution of precipitation. All precipitation products poorly estimated precipitation at higher elevations (〉3,000 m), in drier areas (〈150 mm), and in regions characterized by summer precipitation. All products accurately detected dry spells, but their performance decreased for wet spells with increasing precipitation intensity. In sum, we find that CHIRPS and MSWEP provide the most reliable high‐resolution precipitation estimates for Central Asia. However, the high spatial and temporal heterogeneity of the performance call for a careful selection of a suitable product for local applications considering the prevailing precipitation dynamics, climatic, and topographic conditions.
    Description: We present the first quantitative evaluation of global high‐resolution (below 12 km) precipitation products against independent ground observations over Central Asia. Our results show that MSWEP was best at representing temporal precipitation dynamics, and CHIRPS was most prominent in representing the volume and distribution of precipitation. This is especially the case of wet seasons, altitudes below 3,000 m, and regions dominated by spring and winter precipitation. Our analysis provides key insights on the precipitation products' suitability for local hydrological applications.
    Description: Leibniz‐Institut für Agrarentwicklung in Transformationsökonomien
    Description: Volkswagen Foundation http://dx.doi.org/10.13039/501100001663
    Keywords: ddc:551.6
    Language: English
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    A storyline attribution of the 2011/2012 drought in Southeastern South America (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-08-04
    Description: The 2011/2012 summer drought in Southeastern South America (SESA) was a short but devastating event. What would this event have looked like under pre‐industrial conditions, or in a +2 degC world? We find that climate change causes the region to be at a higher risk of drought. However, we found no large‐scale changes in the half‐month water budgets. We show that the climate change induced positive precipitation trend in the region outweighs the increased temperatures and potential evapotranspiration during the 2011/2012 drought. image
    Keywords: ddc:551.5
    Language: English
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  • 22
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    Inspecting the Reliability of Geochemical Facies Identified for the Waterworks' Capture Zone in Germany (2022)
    Blackwell Publishing Ltd | Malden, US
    Details
    Publication Date: 2022-09-27
    Description: Little research attention has been given to validating clusters obtained from the groundwater geochemistry of the waterworks' capture zone with a prevailing lake‐groundwater exchange. To address this knowledge gap, we proposed a new scheme whereby Gaussian finite mixture modeling (GFMM) and Spike‐and‐Slab Bayesian (SSB) algorithms were utilized to cluster the groundwater geochemistry while quantifying the probability of the resulting cluster membership against each other. We applied GFMM and SSB to 13 geochemical parameters collected during different sampling periods at 13 observation points across the Barnim Highlands plateau located in the northeast of Berlin, Germany; this included 10 observation wells, two lakes, and a gallery of drinking production wells. The cluster analysis of GFMM yielded nine clusters, either with a probability ≥0.8, while the SSB produced three hierarchical clusters with a probability of cluster membership varying from 〈0.2 to 〉0.8. The findings demonstrated that the clustering results of GFMM were in good agreement with the classification as per the principal component analysis and Piper diagram. By superimposing the parameter clustering onto the observation clustering, we could identify discrepancies that exist among the parameters of a certain cluster. This enables the identification of different factors that may control the geochemistry of a certain cluster, although parameters of that cluster share a strong similarity. The GFMM results have shown that from 2002, there has been active groundwater inflow from the lakes towards the capture zone. This means that it is necessary to adopt appropriate measures to reverse the inflow towards the lakes.
    Description: Article impact statement: The probability of cluster membership quantified using an algorithm should be validated against another probabilistic‐based classifier.
    Description: Federal Ministry of Education and Research http://dx.doi.org/10.13039/501100002347
    Keywords: ddc:551.9 ; ddc:551.49
    Language: English
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  • 23
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    Application of mixed‐effects modelling and rule‐based models to explain copper variation in soil profiles of southern Germany (2022)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2022-10-01
    Description: Copper (Cu) is an essential element for plants and microorganisms and at larger concentrations a toxic pollutant. A number of factors controlling Cu dynamics have been reported, but information on quantitative relationships is scarce. We aimed to (i) quantitatively describe and predict soil Cu concentrations (CuAR) in aqua regia considering site‐specific effects and effects of pH, soil organic carbon (SOC) and cation exchange capacity (CEC), and (ii) study the suitability of mixed‐effects modelling and rule‐based models for the analysis of long‐term soil monitoring data. Thirteen uncontaminated long‐term monitoring soil profiles in southern Germany were analysed. Since there was no measurable trend of increasing CuAR concentrations with time in the respective depth ranges of the sites, data from different sampling dates were combined and horizon‐specific regression analyses including model simplifications were carried out for 10 horizons. Fixed‐ and mixed‐effects models with the site as a random effect were useful for the different horizons and significant contributions (either of main effects or interactions) of SOC, CEC and pH were present for 9, 8 and 7 horizons, respectively. Horizon‐specific rule‐based cubist models described the CuAR data similarly well. Validations of cubist models and mixed‐effects models for the CuAR concentrations in A horizons were successful for the given population after random splitting into calibration and validation samples, but not after independent validations with random splitting according to sites. Overall, site, CEC, SOC and pH provide important information for a description of CuAR concentrations using the different regression approaches. Highlights: Information on quantitative relationships for factors controlling Cu dynamics is scarce. Site, CEC, SOC and pH provide important information for a description of Cu concentrations. Validations of cubist models and mixed‐effects models for A horizons were successful for a closed population of sites.
    Description: Bavarian State Ministry of the Environment and Consumer Protection http://dx.doi.org/10.13039/501100010219
    Description: Ministry of Agriculture and Environment Mecklenburg‐Western Pomerania
    Keywords: ddc:631.4
    Language: English
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    Millimetre scale aeration of the rhizosphere and drilosphere (2022)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2022-10-04
    Description: Soil aeration is a critical factor for oxygen‐limited subsoil processes, as transport by diffusion and advection is restricted by the long distance to the free atmosphere. Oxygen transport into the soil matrix is highly dependent on its connectivity to larger pore channels like earthworm and root colonised biopores. Here we hypothesize that the soil matrix around biopores represents different connectivity depending on biopore genesis and actual coloniser. We analysed the soil pore system of undisturbed soil core samples around biopores generated or colonised by roots and earthworms and compared them with the pore system of soil, not in the immediacy of a biopore. Oxygen partial pressure profiles and gas relative diffusion was measured in the rhizosphere and drilosphere from the biopore wall into the bulk soil with microelectrodes. The measurements were linked with structural features such as porosity and connectivity obtained from X‐ray tomography and image analysis. Aeration was enhanced in the soil matrix surrounding biopores in comparison to the bulk soil, shown by higher oxygen concentrations and higher relative diffusion coefficients. Biopores colonised by roots presented more connected lateral pores than earthworm colonised ones, which resulted in enhanced aeration of the rhizosphere compared to the drilosphere. This has influenced biotic processes (microbial turnover/mineralization or root respiration) at biopore interfaces and highlights the importance of microstructural features for soil processes and their dependency on the biopore's coloniser.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:631.4
    Language: English
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    On gravity wave parameterisation in vicinity of low‐level blocking (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-09-22
    Description: This note is framed as an open question to the community regarding parameterisation schemes using the blocking layer depth to reduce the orographic gravity wave drag. It is the purpose of this note to argue that the current orographic gravity wave drag parameterisation in the vicinity of blocking is inadequate. Reducing the gravity wave amplitude (and thereby reducing the gravity wave drag) by assuming an effective mountain height dependent on the blocking depth is not realistic. The arguments given here will hopefully spark a debate and new considerations, ultimately leading to improvements in current orographic gravity wave drag parameterisations. This note illustrates that low‐level blocking can induce more gravity waves or gravity waves with a higher momentum flux (compared to the current parameterisation schemes). More realistic parameterisation schemes are likely to improve the models' performance. However, the fact is complex theories are needed to describe gravity wave excitation by orography so that it is difficult to represent gravity wave nature by a ‘too simple’ parameterisation scheme.
    Description: The purpose of this letter is to provide arguments that the current gravity wave drag parameterisation in the vicinity of blocking is inadequate. Reducing the gravity wave drag depending on the blocking depth is not a realistic representation. The letter lists five ways in which the blocking layer can result in a greater amount of gravity wave drag.
    Keywords: ddc:551.5
    Language: English
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    How close are we to 1.5 degC or 2 degC of global warming? (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-08-09
    Keywords: ddc:551.6
    Language: English
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    Highly resolved modeling of extreme wind speed in North America and Europe (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-08-09
    Description: High wind speed (U) is one of the most dangerous natural hazards in North America and Europe. As a result, spatially explicit, statistical estimation of extreme U is of particular relevance for many sectors. However, the most common sources of wind speed data such as reanalysis data and in situ measurements are limited for this purpose due to their coarse spatial resolution and low representativeness. Thus, the main goal was to develop a high spatial resolution (250 m × 250 m) model (GloWiSMo‐X) for monthly mapping of the maximum hourly U for a 10‐year return period (U10yr) in North America and Europe. The multistep development of GloWiSMo‐X is based on 2544 hourly U time series available from the integrated surface global hourly meteorological data set (UNCEI), U time series from ERA5 (UERA5), and mean wind speed from the Global Wind Speed Model (U¯GloWiSMo). Firstly, the block maxima method was applied to estimate monthly wind speed for a 10‐year return period for both UNCEI (U10yr,NCEI) and UERA5 (U10yr,ERA5). Secondly, the least squares boosting approach was used to predict the target variable U10yr,NCEI yielding the predictions Û10yr. The predictor variables U10yr,ERA5, U¯GloWiSMo, continent, and month were used as input. It was found that the highest monthly continental means of Û10yr (U¯10yr) in January are 16.4 m/s in North America and 16.3 m/s in Europe. U¯10yr dropped to 13.4 m/s and 12.5 m/s in August. The annual cycle of U¯10yr is more pronounced in Europe than in North America. The central parts of the USA and Western Europe were identified as intracontinental regions with the highest U¯10yr. GloWiSMo‐X proves to be very broadly applicable as it covers two different continents and all months. The model validation by the mean squared error (MSE) demonstrates its improved predictive power compared to ERA5.
    Description: A high spatial resolution (250 m × 250 m) model (GloWiSMo‐X) for monthly mapping of the maximum hourly wind speed for a 10‐year return period in North America and Europe was developed. The highest monthly continental means are 16.4 m/s in North America and 16.3 m/s in Europe. Due to the pronounced annual cycle, it drops to 13.4 m/s and 12.5 m/s in August. image
    Description: Bundesministerium für Umwelt, Naturschutz und nukleare Sicherheit
    Keywords: ddc:551.5
    Language: English
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    Responses of soil organic carbon, aggregate diameters, and hydraulic properties to long‐term organic and conventional farming on a Vertisol in India (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-08-09
    Description: Organic matter management can improve soil structural properties. This is crucial for agricultural soils in tropical regions threatened by high rainfall intensities. Compared to conventional farming, organic farming is usually deemed to increase organic carbon and improve soil structural properties such as stability and permeability. However, how much, if any, buildup of organic carbon is possible or indeed occurring also depends on soil type and environmental factors. We compared the impact of seven years of organic farming (annually 13.6 t ha−1 of composted manure) with that of conventional practices (2 t ha−1 of farmyard manure with 150–170 kg N ha−1 of mineral fertilizers) on soil structural properties. The study was conducted on a Vertisol in India with a two‐year crop rotation of cotton soybean wheat. Despite large differences in organic amendment application, organic carbon was not significantly different at 9.6 mg C g−1 on average in the topsoil. However, the size distribution of water‐stable aggregates shifted toward more aggregates 〈137 μm in the organic systems. Cumulative water intake was lower compared to the conventional systems, leading to higher runoff and erosion. These changes might be related to the lower pH and higher exchangeable sodium in the organic systems. Our results indicate that higher application of organic amendments did not lead to higher soil organic carbon and associated improvement in soil structures properties compared to integrated fertilization in this study. Chemical properties may dominate soil aggregation retarding the uptake and integration of organic amendments for sustainable agricultural intensification in tropical, semiarid climates.
    Description: Biovision Foundation for Ecological Development http://dx.doi.org/10.13039/501100015593
    Description: Coop Sustainability Fund
    Description: Swiss Agency for Development and Cooperation (SDC)
    Description: Foundation fiat panis http://dx.doi.org/10.13039/501100011087
    Description: Liechtenstein Development Service http://dx.doi.org/10.13039/501100015698
    Description: https://doi.org/10.6084/m9.figshare.18665612
    Keywords: ddc:631.4
    Language: English
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    Response of subsoil organic matter contents and physical properties to long‐term, high‐rate farmyard manure application (2022)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2022-07-26
    Description: Application of farmyard manure (FYM) is common practice to improve physical and chemical properties of arable soil and crop yields. However, studies on effects of FYM application mainly focussed on topsoils, whereas subsoils have rarely been addressed so far. We, therefore, investigated the effects of 36‐year FYM application with different rates of annual organic carbon (OC) addition (0, 469, 938 and 1875 g C m−2 a−1) on OC contents of a Chernozem in 0–30 cm (topsoil) and 35–45 cm (subsoil) depth. We also investigated its effects on soil structure and hydraulic properties in subsoil. X‐ray computed tomography was used to analyse the response of the subsoil macropore system (≥19 μm) and the distribution of particulate organic matter (POM) to different FYM applications, which were related to contents in total OC (TOC) and water‐extractable OC (WEOC). We show that FYM‐C application of 469 g C m−2 a−1 caused increases in TOC and WEOC contents only in the topsoil, whereas rates of ≥938 g C m−2 a−1 were necessary for TOC enrichment also in the subsoil. At this depth, the subdivision of TOC into different OC sources shows that most of the increase was due to fresh POM, likely by the stimulation of root growth and bioturbation. The increase in subsoil TOC went along with increases in macroporosity and macropore connectivity. We neither observed increases in plant‐available water capacity nor in unsaturated hydraulic conductivity. In conclusion, only very high application of FYM over long periods can increase OC content of subsoil at our study site, but this increase is largely based on fresh, easily degradable POM and likely accompanied by high C losses when considering the discrepancy between OC addition rate by FYM and TOC response in soil. Highlights A new image processing procedure to distinguish fresh and decomposed POM. The increase of subsoil C stock based to a large extend on fresh, labile POM. Potential of arable subsoils for long‐term C storage by large FYM application rates is limited. The increase in TOC has no effect on hydraulic properties of the subsoil.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:631.4
    Language: English
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    Atmospheric circulation patterns that trigger heavy rainfall in West Africa (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-12-05
    Description: Classification of atmospheric circulation patterns (CP) is a common tool for downscaling rainfall, but it is rarely used for West Africa. In this study, a two‐step classification procedure is proposed for this region, which is applied from 1989 to 2010 for the Sudan‐Sahel zone (Central Burkina Faso) with a focus on heavy rainfall. The approach is based on a classification of large‐scale atmospheric CPs (e.g., Saharan Heat Low) of the West African Monsoon using a fuzzy rule‐based method to describe the seasonal rainfall variability. The wettest CPs are further classified using meso‐scale monsoon patterns to better describe the daily rainfall variability during the monsoon period. A comprehensive predictor screening for the seasonal classification indicates that the best performing predictor variables (e.g., surface pressure, meridional moisture fluxes) are closely related to the main processes of the West African Monsoon. In the second classification step, the stream function at 700 hPa for identifying troughs and ridges of tropical waves shows the highest performance, providing an added value to the overall performance of the classification. Thus, the new approach can better distinguish between dry and wet CPs during the rainy season. Moreover, CPs are identified that are of high relevance for daily heavy rainfall in the study area. The two wettest CPs caused roughly half of the extremes on about 6.5% of days. Both wettest patterns are characterized by an intensified Saharan Heat Low and a cyclonic rotation near the study area, indicating a tropical wave trough. Since the classification can be used to condition other statistical approaches used in climate sciences and other disciplines, the presented classification approach opens many different applications for the West African Monsoon region.
    Description: A two‐step classification of daily atmospheric circulation patterns is used to describe seasonal and daily rainfall variability in West Africa. The approach clearly distinguishes between dry and wet patterns if sea level pressure and stream function at 700 hPa are used. The two wettest patterns trigger about half of heavy rainfall events in Central Burkina Faso. They are characterized by an intensified Saharan Heat Low and a cyclonic rotation indicating a tropical wave trough near the study area.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Keywords: ddc:551.5 ; circulation pattern ; classification ; downscaling ; heavy rainfall ; West Africa
    Language: English
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    Bias correction of daily precipitation for ungauged locations using geostatistical approaches: A case study for the CORDEX‐Africa ensemble (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2023-01-14
    Description: Climate model simulations typically exhibit a bias, which can be corrected using statistical approaches. In this study, a geostatistical approach for bias correction of daily precipitation at ungauged locations is presented. The method utilizes a double quantile mapping with dry day correction for future periods. The transfer function of the bias correction for the ungauged locations is established using distribution functions estimated by ordinary kriging with anisotropic variograms. The methodology was applied to the daily precipitation simulations of the entire CORDEX‐Africa ensemble for a study region located in the West African Sudanian Savanna. This ensemble consists of 23 regional climate models (RCM) that were run for three different future scenarios (RCP 2.6, RCP 4.5, and RCP 8.5). The evaluation of the approach for a historical 50‐year period (1950–2005) showed that the method can reduce the inherent strong precipitation bias of RCM simulations, thereby reproducing the main climatological features of the observed data. Moreover, the bias correction technique preserves the climate change signal of the uncorrected RCM simulations. However, the ensemble spread is increased due to an overestimation of the rainfall probability of uncorrected RCM simulations. The application of the bias correction method to the future period (2006–2100) revealed that annual precipitation increases for most models in the near (2020–2049) and far future (2070–2099) with a mean increase of up to 165mm⋅a−1 (18%). An analysis of the monthly and daily time series showed a slightly delayed onset and intensification of the rainy season.
    Description: Adapting water management strategies to future precipitation projected by climate models is associated with high uncertainty in sparsely gauged catchments. Kriging was utilized to estimate distribution parameters for ungauged locations in a West African region to perform a bias correction of the CORDEX‐Africa ensemble. The application of the bias correction method revealed higher annual precipitation amounts and an intensifaction of the rainy season but only little change to the onset of the rainy season.
    Description: German Federal Ministry of Education and Research, Bonn (BMBF), West African Science Service Centre on Climate Change and Adapted Land Use (WASCAL)
    Keywords: ddc:551.6 ; bias correction ; climate change ; CORDEX‐Africa ; geostatistical approaches ; precipitation ; quantile mapping ; West Africa
    Language: English
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    Distribution, drivers and population structure of the invasive alien snail Tarebia granifera in the Luvuvhu system, South Africa (2022)
    Makherana, Fhatuwani ; Cuthbert, Ross N. ; Dondofema, Farai ; [et al.]
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2023-01-14
    Description: Invasive alien species continue to spread and proliferate in waterways worldwide, but environmental drivers of invasion dynamics lack assessment. Knowledge gaps are pervasive in the Global South, where the frequent heavy human‐modification of rivers provides high opportunity for invasion. In southern Africa, the spatio‐temporal ecology of a widespread and high‐impact invasive alien snail, Tarebia granifera, and its management status is understudied. Here, an ecological assessment was conducted at seven sites around Nandoni Reservoir on the Luvuvhu River in South Africa. The distribution and densities of T. granifera were mapped and the potential drivers of population structure were explored. T. granifera was widespread at sites impacted to varying extents due to anthropogenic activity, with densities exceeding 500 individuals per square meter at the most impacted areas. T. granifera predominantly preferred shallow and sandy environments, being significantly associated with sediment (i.e., chlorophyll‐a, Mn, SOC, SOM) and water (i.e., pH, conductivity, TDS) variables. T. granifera seemed to exhibit two recruitment peaks in November and March, identified via size‐based stock assessment. Sediment parameters (i.e., sediment organic matter, sediment organic carbon, manganese) and water chemistry (i.e., pH, total dissolved solids, conductivity) were found to be important in structuring T. granifera populations, with overall snail densities highest during the summer season. We provide important autecological information and insights on the distribution and extent of the spread of T. granifera. This may help in the development of invasive alien snail management action plans within the region, as well as modelling efforts to predict invasion patterns elsewhere based on environmental characteristics.
    Description: Alexander von Humboldt‐Stiftung http://dx.doi.org/10.13039/100005156
    Description: National Research Foundation http://dx.doi.org/10.13039/501100001321
    Description: University of Venda http://dx.doi.org/10.13039/501100008976
    Keywords: ddc:577.6 ; aquatic non‐native invasions ; environmental gradients ; Global South ; human‐modified river ; quilted melania ; reservoir
    Language: English
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    Record summers in Europe: Variations in drought and heavy precipitation during 1901–2018 (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2023-01-13
    Description: During the last 20 years some very hot and dry summers affected Europe, resulting in regionally record‐breaking high temperature or low precipitation values. Long‐term changes of such extremely hot and dry summers are of great relevance for our society, as they are connected with manifold negative impacts on human society, natural ecosystems, and diverse economic sectors. Long‐term variations in drought and five record drought summer half years are studied based on 63 stations across Europe with high‐quality precipitation and temperature time series spanning the period 1901–2018. Eight drought indices are deployed to analyse drought intensity, frequency, and duration; four of them purely precipitation‐based and four integrating potential evapotranspiration in the computation. Additionally, three heavy precipitation indices and simultaneous increases in drought and heavy precipitation are studied. The five driest summer half years over Europe are identified (1947, 2018, 2003, 1921, and 1911). They are analysed by aggregating eight drought indices into the aggregated drought evaluation index (ADE) for five subregions. The ADE shows increasing summer drought conditions over most of Europe, except for some stations in northern Europe. The increase in drought conditions during the warm part of the year is particularly pronounced for indices integrating evapotranspiration in their definition. At the same time, the intensity of heavy precipitation events shows a positive trend, as well as an increased contribution to total precipitation. Several stations in central Europe show simultaneously increasing drought conditions and increasing heavy precipitation events. This increases the risks connected with precipitation extremes.
    Description: Drought and heavy precipitation trends are studied for selected stations with long time series. Both extreme events are related to specific impacts on different economic sectors and thus society. Stations that simultaneously show increasing trends in drought and heavy precipitation mainly occur in central Europe. This indicates a probably higher exposure to these risks in central Europe as well as a demand for broader adaptation options in this region.
    Keywords: ddc:551.6 ; climate indices ; climate variability and change ; dry periods ; mRAI ; WBAI
    Language: English
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    Towards a more comprehensive assessment of the intensity of historical European heat waves (1979–2019) (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2023-01-19
    Description: Europe has been affected by record‐breaking heat waves in recent decades. Using station data and a gridded reanalysis as input, four commonly used heat wave indices, the heat wave magnitude index daily (HWMId), excess heat factor (EHF), wet‐bulb globe temperature (WBGT) and universal thermal climate index (UTCI), are computed. The extremeness of historical European heat waves between 1979 and 2019 using the four indices and different metrics is ranked. A normalisation to enable the comparison between the four indices is introduced. Additionally, a method to quantify the influence of the input parameters on heat wave magnitude is introduced. The spatio‐temporal behaviour of heat waves is assessed by spatial–temporal tracking. The areal extent, large‐scale intensity and duration are visualized using bubble plots. As expected, temperature explains the largest variance in all indices, but humidity is nearly as important in WBGT and wind speed plays a substantial role in UTCI. While the 2010 Russian heat wave is by far the most extreme event in duration and intensity in all normalized indices, the 2018 heat wave was comparable in size for EHF, WBGT and UTCI. Interestingly, the well‐known 2003 central European heat wave was only the fifth and tenth strongest in cumulative intensity in WBGT and UTCI, respectively. The June and July 2019 heat waves were very intense, but short‐lived, thus not belonging to the top heat waves in Europe when duration and areal extent are taken into account. Overall, the proposed normalized indices and the multi‐metric assessment of large‐scale heat waves allow for a more robust description of their extremeness and will be helpful to assess heat waves worldwide and in climate projections.
    Description: Europe has been affected by record‐breaking heat waves in recent decades. Using station data and a gridded reanalysis, the extremeness of European heat waves between 1979 and 2019 is ranked using four indices: heat wave magnitude index daily (HWMId), excess heat factor (EHF), wet‐bulb globe temperature (WBGT) and universal thermal climate index (UTCI). In order to assess heatwaves worldwide and in climate projections, the spatial extent, large‐scale intensity and duration of heatwaves are visualized using bubble plots.
    Description: AXA Research Fund http://dx.doi.org/10.13039/501100001961
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Karlsruher Institut für Technologie http://dx.doi.org/10.13039/100009133
    Keywords: ddc:551.5 ; duration ; heat wave ; indices ; intensity ; large‐scale ; spatial extent
    Language: English
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    Non‐exchangeable stable hydrogen isotope ratios in clay minerals and soil clay fractions: A method test (2022)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2023-01-20
    Description: Stable hydrogen isotope ratios (δ2H values) in structural hydroxyl groups of pedogenic clay minerals are inherited from the surrounding water at the time of their formation. Only non‐exchangeable H preserves the environmental forensic and paleoclimate information (δ2Hn value). To measure δ2Hn values in structural H of clay minerals and soil clay fractions, we adapted a steam equilibration method by accounting for high hygroscopicity. Our δ2Hn values for USGS57 biotite (−95.3 ± SD 0.9‰) and USGS58 muscovite (30.7 ± 1.4‰) differed slightly but significantly from the reported δ2H values (−91.5 ± 2.4‰ and −28.4 ± 1.6‰), because the minerals contained 1.1%–4.4% of exchangeable H. The low SD of replicate measurements (n = 3) confirmed a high precision. The clay separation method including destruction of Fe oxides, carbonates and soil organic matter, and dispersion did not significantly change the δ2Hn values of five different clay minerals. However, we were unable to remove all organic matter from the soil clay fractions resulting in an estimated bias of 1‰ in two samples and 15‰ in the carbon‐richest sample. Our results demonstrate that δ2Hn values of structural H of clay minerals and soil clay fractions can be reliably measured without interference from atmospheric water and the method used to separate the soil clay fraction. Highlights We tested steam equilibration to determine stable isotope ratios of structural H in clay. Gas‐tight capsule sealing in Ar atmosphere was necessary to avoid remoistening. Our steam equilibration method showed a high accuracy and precision. The clay separation method did not change stable isotope ratios of structural H in clay.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:549 ; controlled isotope exchange technique ; deuterium ; montmorillonite ; soil clay separation ; soil organic matter removal ; steam equilibration ; structural H ; USGS57 biotite ; vermiculite ; δ2H
    Language: English
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    Modeling cloud properties over the 79 N Glacier (Nioghalvfjerdsfjorden, NE Greenland) for an intense summer melt period in 2019 (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2023-07-25
    Description: Long believed to be insignificant, melt activity on the Northeast Greenland Ice Stream (NEGIS) has increased in recent years. Summertime Arctic clouds have the potential to strongly affect surface melt processes by regulating the amount of radiation received at the surface. However, the cloud effect over Greenland is spatially and temporally variable and high‐resolution information on the northeast is absent. This study aims at exploring the potential of a high‐resolution configuration of the polar‐optimized Weather Research & Forecasting Model (PWRF) in simulating cloud properties in the area of the Nioghalvfjerdsfjorden Glacier (79 N Glacier). Subsequently, the model simulations are employed to investigate the impact of Arctic clouds on the surface energy budget and on surface melting during the extensive melt event at the end of July 2019. Compared to automatic weather station (AWS) measurements and remote‐sensing data (Sentinel‐2A and the Moderate Resolution Imaging Spectroradiometer, MODIS), PWRF simulates cloud properties with sufficient accuracy. It appears that peak melt was caused by an increase in solar radiation and sensible heat flux (SHF) in response to a blocking anticyclone and foehn winds in the absence of clouds. Cloud warming over high‐albedo surfaces helped to precondition the surface and prolonged the melting as the anticyclone abated. The results are sensitive to the surface albedo and suggest spatiotemporal differences in the cloud effect as snow and ice properties change over the course of the melting season. This demonstrates the importance of including high‐resolution information on clouds in analyses of ice sheet dynamics.
    Description: German Federal Ministry for Education and Research http://dx.doi.org/10.13039/501100002347
    Description: https://doi.org/10.5065/EM0T-1D34
    Description: https://cds.climate.copernicus.eu/cdsapp/#!/search?type=dataset
    Description: https://ladsweb.modaps.eosdis.nasa.gov/search/
    Keywords: ddc:551.5 ; cloud properties ; cloud radiative effect ; Northeast Greenland Ice Stream ; regional climate modeling ; surface energy balance ; surface melt ; surface energy balance ; surface melt
    Language: English
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    Potential erodibility of semi‐arid steppe soils derived from aggregate stability tests (2022)
    Koza, Moritz ; Pöhlitz, Julia ; Prays, Aleksey ; [et al.]
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2023-01-26
    Description: Erosion is a severe threat to the sustainable use of agricultural soils. However, the structural resistance of soil against the disruptive forces steppe soils experience under field conditions has not been investigated. Therefore, 132 topsoils under grass‐ and cropland covering a large range of physico‐chemical soil properties (sand: 2–76%, silt: 18–80%, clay: 6–30%, organic carbon: 7.3–64.2 g kg−1, inorganic carbon: 0.0–8.5 g kg−1, pH: 4.8–9.5, electrical conductivity: 32–946 μS cm−1) from northern Kazakhstan were assessed for their potential erodibility using several tests. An adjusted drop‐shatter method (low energy input of 60 Joule on a 250‐cm3 soil block) was used to estimate the stability of dry soil against weak mechanical forces, such as saltating particles striking the surface causing wind erosion. Three wetting treatments with various conditions and energies (fast wetting, slow wetting, and wet shaking) were applied to simulate different disruptive effects of water. Results indicate that aggregate stability was higher for grassland than cropland soils and declined with decreasing soil organic carbon content. The results of the drop‐shatter test suggested that 29% of the soils under cropland were at risk of wind erosion, but only 6% were at high risk (i.e. erodible fraction 〉60%). In contrast, the fast wetting treatment revealed that 54% of the samples were prone to become “very unstable” and 44% “unstable” during heavy rain or snowmelt events. Even under conditions comparable to light rain events or raindrop impact, 53–59% of the samples were “unstable.” Overall, cropland soils under semi‐arid conditions seem much more susceptible to water than wind erosion. Considering future projections of increasing precipitation in Kazakhstan, we conclude that the risk of water erosion is potentially underestimated and needs to be taken into account when developing sustainable land use strategies. Highlights Organic matter is the important binding agent enhancing aggregation in steppe topsoils. Tillage always declines aggregate stability even without soil organic carbon changes. All croplands soil are prone to wind or water erosion independent of their soil properties. Despite the semi‐arid conditions, erosion risk by water seems higher than by wind.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Keywords: ddc:631.4 ; climate change ; land use ; soil organic carbon ; soil texture ; water erosion ; wind erosion
    Language: English
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    Vertical SOC distribution and aromatic carbon in centuries old charcoal‐rich Technosols (2022)
    Bonhage, Alexander ; Raab, Thomas ; Schneider, Anna ; [et al.]
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2023-01-21
    Description: Charcoal‐rich Technosols on century‐old relict charcoal hearths (RCHs) are the subject of ongoing research regarding potential legacy effects that result from historic charcoal production and subsequent charcoal amendments on forest soil properties and forest ecosystems today. RCHs consist mostly of Auh horizons that are substantially enriched in soil organic carbon (SOC), of which the largest part seems to be of pyrogenic origin (PyC). However, the reported range of SOC and PyC contents in RCH soil also suggests that they are enriched in nonpyrogenic SOC. RCH soils are discussed as potential benchmarks for the long‐term influence of biochar amendment and the post‐wildfire influences on soil properties. In this study, we utilised a large soil sample dataset (n = 1245) from 52 RCH sites in north‐western Connecticut, USA, to quantify SOC contents by total element analysis. The contents of condensed highly aromatic carbon as a proxy for black carbon (BC) were predicted by using a modified benzene polycarboxylated acid (BPCA) marker method in combination with diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy‐based partial least square regression (r2 = 0.89). A high vertical spatial sampling resolution allowed the identification of soil organic matter (SOM) enrichment and translocation processes. The results show an average 75% and 1862% increase in TOC and BPCA‐derived carbon, respectively, for technogenic Auh horizons compared to reference soils. In addition to an increase in aromatic properties, increased carboxylic properties of the RCH SOC suggest self‐humification effects of degrading charcoal and thereby the continuing formation of leachable aromatic carbon compounds, which could have effects on pedogenic processes in buried soils. Indeed, we show BPCA‐derived carbon concentrations in intermediate technogenic Cu horizons and buried top/subsoils that suggest vertical translocation of highly aromatic carbon originating in RCH Auh horizons. Topmost Auh horizons showed a gradual decrease in total organic carbon (TOC) contents with increasing depth, suggesting accumulation of recent, non‐pyrogenic SOM. Lower aliphatic absorptions in RCH soil spectra suggest different SOM turnover dynamics compared to reference soils. Furthermore, studied RCH soils featured additional TOC enrichment, which cannot be fully explained now. Highlights BC to TOC ratio and high resolution vertical SOC distribution in 52 RCH sites were studied. RCH soils non‐BC pool was potentially different to reference soils. RCH soils feature TOC accumulation in the topmost horizon. There is BC translocation into buried soils on RCH sites.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:631.4 ; benzene polycarboxylated acid marker (BPCA) ; black carbon ; charcoal degradation ; charcoal kiln ; pyrogenic carbon ; relict charcoal hearth ; biochar
    Language: English
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    Defining Hydrogeological Site Similarity with Hierarchical Agglomerative Clustering (2022)
    Blackwell Publishing Ltd | Malden, US
    Details
    Publication Date: 2024-02-28
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Hydrogeological information about an aquifer is difficult and costly to obtain, yet essential for the efficient management of groundwater resources. Transferring information from sampled sites to a specific site of interest can provide information when site‐specific data is lacking. Central to this approach is the notion of site similarity, which is necessary for determining relevant sites to include in the data transfer process. In this paper, we present a data‐driven method for defining site similarity. We apply this method to selecting groups of similar sites from which to derive prior distributions for the Bayesian estimation of hydraulic conductivity measurements at sites of interest. We conclude that there is now a unique opportunity to combine hydrogeological expertise with data‐driven methods to improve the predictive ability of stochastic hydrogeological models.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉〈italic〉Article impact statement〈/italic〉: This article introduces hierarchical clustering as a method for defining a notion of site similarity; the aim of this method is to improve the derivation of prior distributions in Bayesian methods in hydrogeology.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: https://github.com/GeoStat-Bayesian/geostatDB
    Description: https://github.com/GeoStat-Bayesian/exPrior
    Description: https://github.com/GeoStat-Bayesian/siteSimilarity
    Keywords: ddc:551.49 ; hydrogeological sites ; hydrogeological modeling
    Language: English
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  • 40
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    How certain are El Niño–Southern Oscillation frequency changes in Coupled Model Intercomparison Project Phase 6 models? (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-02-06
    Description: El Niño–Southern Oscillation (ENSO) is one of the most important modes of climate variability on interannual timescales. We aim to find out whether a change in ENSO frequency can be predicted for the nearer future. We analyse the unforced pre‐industrial control run and the forced 1%/year CO〈sub〉2〈/sub〉 increase run for an ensemble of 43 general circulation models that participated in the Coupled Model Intercomparison Project Phase 6 (CMIP6). We assume that the uncertainty of ENSO frequency trend estimates from an ensemble is caused by apparent trends as well as model differences. The part of the uncertainty caused by apparent trends is estimated from the pre‐industrial control simulations. As a measure for ENSO frequency, we use the number of El Niño‐ and La Niña‐like months in a moving 30‐year time window. Its linear decadal trend is calculated for every member. The multimember mean of the trend for both experiments is less than 0.7 events per decade. Given that the standard error is of the same order of magnitude, we consider this a negligible trend. The uncertainties are large in both experiments and we can attribute most of the intermember variability to apparent trends due to natural variability rather than different model reactions to CO〈sub〉2〈/sub〉 forcing. This means that the impact of intermodel differences might have been overstated in previous studies. Apparent trends make it very difficult to make reliable predictions of changes in ENSO frequency based on 120‐year time series.
    Description: The 1pctCO2 and piControl ensembles from CMIP6 are analysed for 43 models with a focus on changes in ENSO frequency. We find that most of the intermember variability can be attributed to natural variability instead of model differences. Therefore, the uncertainty can only marginally be reduced and it is very difficult to reliably predict changes in ENSO frequency on a timescale of 150 years.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: https://doi.org/10.5281/zenodo.6841964
    Keywords: ddc:551.6 ; climate change ; CMIP6 ; ENSO ; ENSO frequency
    Language: English
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  • 41
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    On the representation of atmospheric circulation modes in regional climate models over Western Europe (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2023-12-16
    Description: Atmospheric circulation is a key driver of climate variability, and the representation of atmospheric circulation modes in regional climate models (RCMs) can enhance the credibility of regional climate projections. This study examines the representation of large‐scale atmospheric circulation modes in Coupled Model Inter‐comparison Project phase 5 RCMs once driven by ERA‐Interim, and by two general circulation models (GCMs). The study region is Western Europe and the circulation modes are classified using the Promax rotated T‐mode principal component analysis. The results indicate that the RCMs can replicate the classified atmospheric modes as obtained from ERA5 reanalysis, though with biases dependent on the data providing the lateral boundary condition and the choice of RCM. When the boundary condition is provided by ERA‐Interim that is more consistent with observations, the simulated map types and the associating time series match well with their counterparts from ERA5. Further, on average, the multi‐model ensemble mean of the analysed RCMs, driven by ERA‐Interim, indicated a slight improvement in the representation of the modes obtained from ERA5. Conversely, when the RCMs are driven by the GCMs that are models without assimilation of observational data, the representation of the atmospheric modes, as obtained from ERA5, is relatively less accurate compared to when the RCMs are driven by ERA‐Interim. This suggests that the biases stem from the GCMs. On average, the representation of the modes was not improved in the multi‐model ensemble mean of the five analysed RCMs driven by either of the GCMs. However, when the best‐performed RCMs were selected on average the ensemble mean indicated a slight improvement. Moreover, the presence of the North Atlantic Oscillation (NAO) in the simulated modes depends also on the lateral boundary conditions. The relationship between the modes and the NAO was replicated only when the RCMs were driven by reanalysis. The results indicate that the forcing model is the main factor in reproducing the atmospheric circulation.
    Keywords: ddc:551.6 ; general circulation model ; large‐scale atmospheric circulation modes ; multi‐model ensemble ; regional climate model ; Western Europe
    Language: English
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  • 42
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    Understanding summer wind systems over the eastern Mediterranean in a high‐resolution climate simulation (2022)
    Latt, Melissa R. ; Hochman, Assaf ; Caldas‐Alvarez, Alberto ; [et al.]
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-01-12
    Description: Regional and local wind systems are often complex, particularly near coastal areas with a highly variable orography. Thus, the realistic representation of regional wind systems in weather and climate models is of strong relevance. Here, we evaluate the ability of a 13‐year convection‐permitting climate simulation in reproducing the interaction of several regional summer wind systems over the complex orography in the eastern Mediterranean region. The COSMO‐CLM simulations are driven by hourly ERA‐5 reanalysis and have a spatial resolution of 2.8 and 7.0 km. The simulated near‐surface wind fields are compared with unique very high‐resolution wind observations collected within the “Dead Sea Research Venue” project (DESERVE) and data from the Israel Meteorological Service synop network. The high‐resolution COSMO‐CLM simulations largely reproduce the main characteristics of the regional wind systems (Mediterranean and Dead Sea breeze, slope winds in the Judean Mountains and winds along the Jordan Rift valley), whereas ERA‐5 is only able to represent the Mediterranean Sea breeze. The high‐resolution simulations substantially improve the representation of regional winds, particularly over complex orography. Indeed, the 2.8 km simulation outperforms the 7.0 km run, on 88% of the days. Two mid‐July 2015 case studies show that only the 2.8 simulation can realistically simulate the penetration of the Mediterranean Sea Breeze into the Jordan Rift valley and complex interactions with other wind systems like the Dead Sea breeze. Our results may have profound implications for regional weather and climate prediction since very high‐resolution information seems to be necessary to reproduce the main summertime climatic features in this region. We envisage that such simulations may also be required at other regions with complex orography.
    Description: In this paper we show that COSMO‐CLM regional climate model simulations at 7.0 (CLM‐7.0) and 2.8km (CLM‐2.8) resolution can realistically reproduce near‐surface regional and local wind systems over the complex orography of the eastern Mediterranean as opposite to coarser resolutions (ERA‐5, 31 km). The Mediterranean and local Dead Sea breezes, slope winds over the Judean Mountains, and winds along the Jordan Rift valley are well represented both climatologically and on individual days. CLM‐2.8 captures the small‐scale variability of the wind field better than CLM‐7.0 particularly near the Dead Sea and on 88% of the days CLM‐2.8 represents wind speed even more realistically than CLM‐7.0. image
    Description: German Helmholtz Association (“Changing Earth” program)
    Description: AXA Research Fund http://dx.doi.org/10.13039/501100001961
    Description: Ministry of Science, Research and Arts
    Description: Helmholtz Association of German Research Centers
    Keywords: ddc:551.6 ; complex orography ; convection permitting ; COSMO‐CLM ; Dead Sea ; eastern Mediterranean ; grid spacing ; regional climate modelling ; sea breeze
    Language: English
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    Using hydro‐morphological assessment parameters to estimate the flood‐induced vulnerability of watercourses ‐ a methodological approach across three spatial scales in Germany and the Czech Republic (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-01-22
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉In addition to their ecological importance, rivers and streams have always been used in diverse ways by humans, resulting in the development of settlements and their connected built environments along many of the world's watercourses. During heavy rainfall, buildings, traffic infrastructure and water‐related infrastructure are exposed to potential hazards in the form of (flash) floods. In contrast to near‐natural watercourses, anthropogenically modified channels in urban areas are particularly susceptible to damage by flooding. Previous damage assessments have highlighted the need to forecast such damage to watercourses in order to identify critical areas and justify the selection and expansion of adaptation measures. Within the scope of the current study, we have developed a method based on the hydro‐morphological properties of watercourses to make transferable estimates of the economic damage potential based on ecologically‐relevant parameters. Using a scale‐specific cause‐effect analysis, we have identified characteristics of the watercourse type and adjacent structures as well as construction‐related properties of reinforcements that can increase the damage potential during flooding. In this way, we are able to show that several influencing factors determine the vulnerability of watercourses: in addition to the specific longitudinal gradient and size (macroscale) of various watercourse types, damage‐relevant boundary conditions in watercourse sections (mesoscale) and the resistance of typical bed and bank constructions are also important, reflecting the specific structural conditions. Taking rivers in Germany and the Czech Republic as case studies, in the following, we review the local identification of critical areas and describe the necessary data management. The presented “Hydro‐morphological based Vulnerability Assessment‐Concept (HyVAC)” can contribute to the flood damage prevention at watercourses by utilizing existing basic data to the greatest possible extent and thus is suitable for preliminary investigations according to the EC Flood Risk Management Directive.〈/p〉
    Description: STRIMA II
    Description: EU‐funded research project
    Keywords: ddc:551.48 ; assessment parameters ; flood risk management ; hydro‐morphology ; vulnerability ; watercourses
    Language: English
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  • 44
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    Reducing tillage intensity benefits the soil micro‐ and mesofauna in a global meta‐analysis (2022)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2024-03-22
    Description: Soil fauna drives crucial processes of energy and nutrient cycling in agricultural systems, and influences the quality of crops and pest incidence. Soil tillage is the most influential agricultural manipulation of soil structure, and has a profound influence on soil biology and its provision of ecosystem services. The objective of this study was to quantify through meta‐analyses the effects of reducing tillage intensity on density and diversity of soil micro‐ and mesofaunal communities, and how these effects vary among different pedoclimatic conditions and interact with concurrent management practices. We present the results of a global meta‐analysis of available literature data on the effects of different tillage intensities on taxonomic and functional groups of soil micro‐ and mesofauna. We collected paired observations (conventional vs. reduced forms of tillage/no‐tillage) from 133 studies across 33 countries. Our results show that reduced tillage intensity or no‐tillage increases the total density of springtails (+35%), mites (+23%), and enchytraeids (+37%) compared to more intense tillage methods. The meta‐analyses for different nematode feeding groups, life‐forms of springtails, and taxonomic mite groups showed higher densities under reduced forms of tillage compared to conventional tillage on omnivorous nematodes (+53%), epedaphic (+81%) and hemiedaphic (+84%) springtails, oribatid (+43%) and mesostigmatid (+57%) mites. Furthermore, the effects of reduced forms of tillage on soil micro‐ and mesofauna varied with depth, climate and soil texture, as well as with tillage method, tillage frequency, concurrent fertilisation, and herbicide application. Our findings suggest that reducing tillage intensity can have positive effects on the density of micro‐ and mesofaunal communities in areas subjected to long‐term intensive cultivation practices. Our results will be useful to support decision making on the management of soil faunal communities and will facilitate modelling efforts of soil biology in global agroecosystems. HIGHLIGHTS Global meta‐analysis to estimate the effect of reducing tillage intensity on micro‐ and mesofauna Reduced tillage or no‐tillage has positive effects on springtail, mite and enchytraeid density Effects vary among nematode feeding groups, springtail life forms and mite suborders Effects vary with texture, climate and depth and depend on the tillage method and frequency
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: https://doi.org/10.20387/bonares-eh0f-hj28
    Keywords: ddc:631.4 ; agricultural land use ; conservation agriculture ; conventional agriculture ; soil biodiversity ; soil cultivation
    Language: English
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  • 45
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    Modelling wind speed across Zambia: Implications for wind energy (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-03-25
    Description: Wind energy is a key option in global dialogues about climate change mitigation. Here, we combined observations from surface wind stations, reanalysis datasets, and state‐of‐the‐art regional climate models from the Coordinated Regional Climate Downscaling Experiment (CORDEX Africa) to study the current and future wind energy potential in Zambia. We found that winds are dominated by southeasterlies and are rarely strong with an average speed of 2.8 m·s〈sup〉−1〈/sup〉. When we converted the observed surface wind speed to a turbine hub height of 100 m, we found a ~38% increase in mean wind speed for the period 1981–2000. Further, both simulated and observed wind speed data show statistically significant increments across much of the country. The only areas that divert from this upward trend of wind speeds are the low land terrains of the Eastern Province bordering Malawi. Examining projections of wind power density (WPD), we found that although wind speed is increasing, it is still generally too weak to support large‐scale wind power generation. We found a meagre projected annual average WPD of 46.6 W·m〈sup〉−2〈/sup〉. The highest WPDs of ~80 W·m−2 are projected in the northern and central parts of the country while the lowest are to be expected along the Luangwa valley in agreement with wind speed simulations. On average, Zambia is expected to experience minor WPD increments of 0.004 W·m〈sup〉−2〈/sup〉 per year from 2031 to 2050. We conclude that small‐scale wind turbines that accommodate cut‐in wind speeds of 3.8 m·s〈sup〉−1〈/sup〉 are the most suitable for power generation in Zambia. Further, given the limitations of small wind turbines, they are best suited for rural and suburban areas of the country where obstructions are few, thus making them ideal for complementing the government of the Republic of Zambia's rural electrification efforts.
    Description: Wind speed is very slow in Zambia. It is increasing but remains unlikely to support large commercial wind farms especially not at the 100‐m hub height. Any efforts for wind power generation in Zambia should be towards ultra‐tall wind turbines fitted with larger rotors.
    Description: Alexander von Humboldt‐Stiftung
    Keywords: ddc:333.9 ; CORDEX Africa ; renewable energy ; wind speed ; Zambia
    Language: English
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  • 46
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    Evaluating learning spaces in flood risk management in Germany: Lessons for governance research (2021)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2021-06-28
    Description: Efforts to collaboratively manage the risk of flooding are ultimately based on individuals learning about risks, the decision process, and the effectiveness of decisions made in prior situations. This article argues that much can be learned about a governance setting by explicitly evaluating the relationships through which influential individuals and their immediate contacts receive and send information to one another. We define these individuals as “brokers,” and the networks that emerge from their interactions as “learning spaces.” The aim of this article is to develop strategies to identify and evaluate the properties of a broker's learning space that are indicative of a collaborative flood risk management arrangement. The first part of this article introduces a set of indicators, and presents strategies to employ this list so as to systematically identify brokers, and compare their learning spaces. The second part outlines the lessons from an evaluation that explored cases in two distinct flood risk management settings in Germany. The results show differences in the observed brokers' learning spaces. The contacts and interactions of the broker in Baden‐Württemberg imply a collaborative setting. In contrast, learning space of the broker in North Rhine‐Westphalia lacks the same level of diversity and polycentricity.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: MWK Baden‐Württemberg
    Keywords: 333.91 ; brokerage ; collaborative water governance ; comanagement ; comparative analysis ; social networks
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  • 47
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    Extreme precipitation events in the Mediterranean: Spatiotemporal characteristics and connection to large‐scale atmospheric flow patterns (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-01
    Description: The Mediterranean region is strongly affected by extreme precipitation events (EPEs), sometimes leading to severe negative impacts on society, economy, and the environment. Understanding such natural hazards and their drivers is essential to mitigate related risks. Here, EPEs over the Mediterranean between 1979 and 2019 are analysed, using ERA5, the latest reanalysis dataset from ECMWF. EPEs are determined based on the 99th percentile of their daily distribution (P99). The different EPE characteristics are assessed, based on seasonality and spatiotemporal dependencies. To better understand their connection to large‐scale atmospheric flow patterns, Empirical Orthogonal Function analysis and subsequent non‐hierarchical K‐means clustering are used to quantify the importance of weather regimes to EPE frequency. The analysis is performed for different variables, depicting atmospheric variability in the lower and middle troposphere. Results show a clear spatial division in EPE occurrence, with winter and autumn being the seasons of highest EPE frequency for the eastern and western Mediterranean, respectively. There is a high degree of temporal dependencies with 20% of the EPEs (median value based on all studied grid cells), occurring up to 1 week after a preceding P99 event at the same location. Local orography is a key modulator of the spatiotemporal connections and substantially enhances the probability of co‐occurrence of EPEs even for distant locations. The clustering clearly demonstrates the prevalence of distinct synoptic‐scale atmospheric conditions during the occurrence of EPEs for different locations within the region. Results indicate that clustering, based on a combination of sea level pressure (SLP) and geopotential height at 500 hPa (Z500), can increase the conditional probability of EPEs by more than three (3) times (median value for all grid cells) from the nominal probability of 1% for the P99 EPEs. Such strong spatiotemporal dependencies and connections to large‐scale patterns can support extended‐range forecasts.
    Description: This study analyses the spatiotemporal characteristics of extreme precipitation events over the Mediterranean, and their connection to large‐scale atmospheric flow patterns. It is shown that by conditioning the extremes based on the atmospheric variability in the low‐ and mid‐troposphere, their probability increases more than threefold, when using nine clusters to group all the synoptic daily patterns. This finding can support extended‐range forecasts, as for such lead times the NWP models are more skillful in predicting large‐scale patterns than localized extremes.
    Description: Marie Skłodowska‐Curie
    Description: European Union's Horizon 2020
    Keywords: 551.6 ; extreme precipitation ; large‐scale/circulation patterns ; Mediterranean ; weather regimes
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  • 48
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    Prioritizing reaches for restoration in a regulated Alpine river: Locally driven versus hydro‐morphologically based actions (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-06-27
    Description: We discuss the prioritization of river reaches to be selected for restoration measures under the constraints of financial resource limitation. We propose and apply a simple approach based on the quantification of major hydro‐morphological alterations and the critical comparison with locally proposed restoration actions. The available hydro‐morphological and ecological data for the approach do not go beyond the requirements posed by the implementation of the EU Water Framework and Floods Directives. We describe an example that refers to a heavily regulated Alpine river (Sarca River, NE Italy). The results indicate hydropower facilities as a key source of hydrological alteration, with sediment retention and grade control structures on lateral tributaries playing an additional relevant role in reducing sediment supply. The frequency and duration of sediment‐transporting floods have dramatically decreased, and the bed sediment composition has been markedly altered and become highly compacted. Habitat improvement has been achieved after the implementation of minimum environmental flows. The comparison between the results of the hydro‐morphological indicators and the locally proposed restoration actions highlights that reaches with lower degree of hydro‐morphological alterations do not coincide with the areas chosen for the locally planned actions, which often miss considerations of the relevant spatial scales. In a context of limited available financial resources and data compared to other flagship river restoration projects in the European Alps, the present work suggests viable options for the choice of target restoration reaches.
    Description: Consorzio dei Comuni BIM Sarca
    Description: Italian Ministry of Education, University and Research (MIUR)
    Description: Rete di Riserve della Sarca
    Keywords: 333.91 ; ecological flows ; hydropower ; regulated rivers ; sediment transport
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  • 49
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    Extreme precipitation events over northern Italy. Part II: Dynamical precursors (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-20
    Description: The connection between weather extremes and Rossby wave packets (RWP) has been increasingly documented in recent years. RWP propagation and characteristics can modulate the midlatitude weather, setting the scene for temperature and precipitation extremes and controlling the geographical area affected. Several studies on extreme precipitation events (EPEs) in the Alpine area reported, as the main triggering factor, a meridionally elongated upper‐level trough as part of an incoming Rossby wave packet. In this work, we investigate a wide number of EPEs occurring between 1979 and 2015 in northern‐central Italy. The EPEs are subdivided into three categories (Cat1, Cat2, Cat3) according to thermodynamic conditions over the affected region. It is found that the three categories differ not only in terms of the local meteorological conditions, but also in terms of the evolution and properties of precursor RWPs. These differences cannot be solely explained by the apparent seasonality of the flow; therefore, the relevant physical processes in the RWP propagation of each case are further investigated. In particular, we show that RWPs associated with the strongest EPEs, namely the ones falling in Cat2, undergo a substantial amplification over the western North Atlantic due to anomalous ridge‐building 2 days before the event; arguably due to diabatic heating sources. This type of development induces a downstream trough which is highly effective in focusing water vapour transport toward the main orographic barriers of northern‐central Italy and favouring the occurrence of EPEs.
    Description: The EPEs are subdivided into three categories (Cat1, Cat2, Cat3) according to thermodynamic conditions over the affected region. The three categories not only differ locally but also in the evolution of precursor RWPs as visible in the composite Hovmöller plots. RWPs associated with the strongest EPEs, the ones falling in Cat2, undergo a substantial amplification over the west North Atlantic due to anomalous ridge‐building 2 days before the event. This type of development induces a downstream trough which is highly effective in focusing water vapour transport toward the Apennines and the Alps.
    Description: Ludwig‐Maximilians‐Universität München http://dx.doi.org/10.13039/501100005722
    Description: German Research Foundation (DFG)
    Description: Transregional Collaborative Research Centre
    Keywords: 551.6 ; atmospheric rivers ; extreme precipitation ; integrated water vapour transport ; large‐scale forcing ; potential vorticity ; Rossby wave packets
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    Synthetic resampling strategies and machine learning for digital soil mapping in Iran (2021)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2021-07-04
    Description: Most common machine learning (ML) algorithms usually work well on balanced training sets, that is, datasets in which all classes are approximately represented equally. Otherwise, the accuracy estimates may be unreliable and classes with only a few values are often misclassified or neglected. This is known as a class imbalance problem in machine learning and datasets that do not meet this criterion are referred to as imbalanced data. Most datasets of soil classes are, therefore, imbalanced data. One of our main objectives is to compare eight resampling strategies that have been developed to counteract the imbalanced data problem. We compared the performance of five of the most common ML algorithms with the resampling approaches. The highest increase in prediction accuracy was achieved with SMOTE (the synthetic minority oversampling technique). In comparison to the baseline prediction on the original dataset, we achieved an increase of about 10, 20 and 10% in the overall accuracy, kappa index and F‐score, respectively. Regarding the ML approaches, random forest (RF) showed the best performance with an overall accuracy, kappa index and F‐score of 66, 60 and 57%, respectively. Moreover, the combination of RF and SMOTE improved the accuracy of the individual soil classes, compared to RF trained on the original dataset and allowed better prediction of soil classes with a low number of samples in the corresponding soil profile database, in our case for Chernozems. Our results show that balancing existing soil legacy data using synthetic sampling strategies can significantly improve the prediction accuracy in digital soil mapping (DSM). Highlights Spatial distribution of soil classes in Iran can be predicted using machine learning (ML) algorithms. The synthetic minority oversampling technique overcomes the drawback of imbalanced and highly biased soil legacy data. When combining a random forest model with synthetic sampling strategies the prediction accuracy of the soil model improves significantly. The resulting new soil map of Iran has a much higher spatial resolution compared to existing maps and displays new soil classes that have not yet been mapped in Iran.
    Description: Alexander von Humboldt‐Stiftung http://dx.doi.org/10.13039/100005156
    Description: German Research Foundation http://dx.doi.org/10.13039/501100001659
    Description: Soil and Water Research Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran
    Keywords: 631.4 ; covariates ; imbalanced data ; machine learning ; random forest ; soil legacy data
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    WRF‐based dynamical downscaling of ERA5 reanalysis data for High Mountain Asia: Towards a new version of the High Asia Refined analysis (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-03
    Description: The High Asia Refined analysis (HAR) is a regional atmospheric data set generated by dynamical downscaling of the Final operational global analysis (FNL) using the Weather Research and Forecasting (WRF) model. It has been successfully and widely utilized. A new version (HAR v2) with longer temporal coverage and extended domains is currently under development. ERA5 reanalysis data is used as forcing data. This study aims to find the optimal set‐up for the production of the HAR v2 to provide similar or even better accuracy as the HAR. First, we conducted a sensitivity study, in which different cumulus, microphysics, planetary boundary layer, and land surface model schemes were compared and validated against in situ observations. The technique for order preference by similarity to the ideal solution (TOPSIS) method was applied to identify the best schemes. Snow depth in ERA5 is overestimated in High Mountain Asia (HMA) and causes a cold bias in the WRF output. Therefore, we used Japanese 55‐year Reanalysis (JRA‐55) to correct snow depth initialized from ERA5 based on the linear scaling approach. After applying the best schemes identified by the TOPSIS method and correcting the initial snow depth, the model performance improves. Finally, we applied the improved set‐up for the HAR v2 and computed a one‐year run for 2011. Compared to the HAR, the HAR v2 has a better representation of air temperature at 2 m. It produces slightly higher precipitation amounts, but the spatial distribution of seasonal mean precipitation is closer to observations.
    Description: German Federal Ministry of Education and Research (BMBF) http://dx.doi.org/10.13039/501100002347
    Keywords: 551.5 ; cold bias ; dynamical downscaling ; ERA5 ; HAR ; High Mountain Asia ; snow depth ; WRF
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    Hydro Explorer: An interactive web app to investigate changes in runoff timing and runoff seasonality all over the world (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-06-27
    Description: Climatic changes and anthropogenic modifications of the river basin or river network have the potential to fundamentally alter river runoff. In the framework of this study, we aim to analyze and present historic changes in runoff timing and runoff seasonality observed at river gauges all over the world. In this regard, we develop the Hydro Explorer, an interactive web app, which enables the investigation of 〉7,000 daily resolution discharge time series from the Global Runoff Data Centre (GRDC). The interactive nature of the developed web app allows for a quick comparison of gauges, regions, methods, and time frames. We illustrate the available analytical tools by investigating changes in runoff timing and runoff seasonality in the Rhine River Basin. Since we provide the source code of the application, existing analytical approaches can be modified, new methods added, and the tool framework can be re‐used to visualize other data sets.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: WOA Institution: UNIVERSITAET POTSDAM Blended DEAL: ProjektDEAL
    Keywords: 551.488 ; global runoff database ; interactive web app ; R Shiny ; runoff seasonality ; runoff timing
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    Impact of biochar on nutrient supply, crop yield and microbial respiration on sandy soils of northern Germany (2021)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2021-06-16
    Description: The application of biochar to agricultural soils to increase nutrient availability, crop production and carbon sequestration has gained increasing interest but data from field experiments on temperate, marginal soils are still under‐represented. In the current study, biochar, produced from organic residues (digestates) from a biogas plant, was applied with and without digestates at low (3.4 t ha−1) and intermediate (17.1 t ha−1) rates to two acidic and sandy soils in northern Germany that are used for corn (Zea mays L.) production. Soil nutrient availability, crop yields, microbial biomass and carbon dioxide (CO2) emissions from heterotrophic respiration were measured over two consecutive years. The effects of biochar application depended on the intrinsic properties of the two tested soils and the biochar application rates. Although the soils at the fallow site, with initially low nutrient concentrations, showed a significant increase in pH, soil nutrients and crop yield after low biochar application rates, a similar response was found at the cornfield site only after application of substantially larger amounts of biochar. The effect of a single dose of biochar at the beginning of the experiment diminished over time but was still detectable after 2 years. Whereas plant available nutrient concentrations increased after biochar application, the availability of potentially phytotoxic trace elements (Zn, Pb, Cd, Cr) decreased significantly, and although slight increases in microbial biomass carbon and heterotrophic CO2 fluxes were observed after biochar application, they were mostly not significant. The results indicate that the application of relatively small amounts of biochar could have positive effects on plant available nutrients and crop yields of marginal arable soils and may decrease the need for mineral fertilizers while simultaneously increasing the sequestration of soil organic carbon. Highlights A low rate of biochar increased plant available nutrients and crop yield on marginal soils. Biochar application reduced the availability of potentially harmful trace elements. Heterotrophic respiration showed no clear response to biochar application. Biochar application may reduce fertilizer need and increase carbon sequestration on marginal soils.
    Description: German Academic Exchange Service http://dx.doi.org/10.13039/501100001655
    Description: Institute Strategic Programme grants, “Soils to Nutrition”
    Keywords: 631.4 ; black carbon ; carbon sequestration ; corn ; digestate ; heterotrophic respiration ; marginal soils ; microbial biomass
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    Unusual appearance of mother‐of‐pearl clouds above El Calafate, Argentina (50°21′S, 72°16′W) (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-04-29
    Description: Visual observations from the ground and from a glider soaring in the lowermost stratosphere revealed the existence of stratospheric mother‐of‐pearl clouds above El Calafate in the lee of the Andes on 11 September 2019. The appearance of these clouds is rather unusual considering the time – end of the austral winter – and the location at about 50°S, being far away from Antarctica. This paper presents the available observations and describes the overall meteorological situation that was related to the earliest sudden stratospheric warming recorded so far in the Southern Hemisphere. By using high‐resolution numerical simulations, we show evidence of mountain waves propagating up to the stratosphere that are responsible for generating the localised cold stratospheric temperature anomalies required for ice cloud formation. Snapshots of a mother‐of‐pearl cloud from the camera installed at the PERLAN 2 aircraft's tail wing. image
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 551.5 ; Argentina ; ice cloud formation
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    A new approach to classification of 40 years of Antarctic sea ice concentration data (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-04
    Description: In this paper, we present a characterization of Antarctic sea ice based on the classification of annual sea ice concentration (SIC) data from 1979 to 2018. A clustering algorithm was applied to provide a climatological description of significant annual cycles of SIC and their spatial distribution around the Southern Ocean. Based on these classification results, we investigate the variability of SIC cycles on decadal and inter‐annual time scales. First, we discuss significant spatial shifts of SIC cycles during 1979–1998 and 1999–2018. In the Weddell Sea and in large parts of the Ross Sea, we observed higher SIC during the summer season, and an extension of sea ice cover in winter compared to the long‐term average. Second, we introduce the Climatological Sea Ice Anomaly Index (CSIAI), which is an annual measure for year‐round sea ice anomalies of the Southern Ocean and its regional sub‐sectors. By relating selected years of significant sea ice conditions (1981, 2007 and 2014) with atmospheric influences, we demonstrate that the CSIAI is very useful for assessing inter‐annular Antarctic SIC variability. Positive and negative sea ice anomalies can be qualitatively explained by atmospheric circulation anomalies in the years 1981 and 2007. However, in 2014, the year with the largest observed sea ice extent in our time series, we found that this positive sea ice anomaly was surprisingly not associated with a stationary and inter‐seasonally persistent pattern of circulation anomaly. This suggests that sub‐seasonal to seasonal circulation anomalies and ocean‐related processes favoured the formation of the sea ice maximum in 2014. With this study we provide additional information on the long‐term annual SIC variability around Antarctica. Furthermore, our classification approach and its results have potential for application in the evaluation of sea ice model results.
    Description: In this paper, we present a characterization of Antarctic sea ice based on the classification of annual sea ice concentration cycles in the period 1979 to 2018. Furthermore, we discuss spatial shifts between 1979–1998 and 1999–2018 and are able to explain significant annual sea ice anomalies by atmospheric circulation anomalies.
    Description: DLR Management Board: Young Investigator Group Leader Program. F.R. was funded by the Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 551.31 ; passive microwave data ; sea ice climatology ; sea ice trends ; sea ice variability
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    Self‐stated recovery from flooding: Empirical results from a survey in Central Vietnam (2021)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2021-06-27
    Description: Social inequalities lead to flood resilience inequalities across social groups, a topic that requires improved documentation and understanding. The objective of this paper is to attend to these differences by investigating self‐stated flood recovery across genders in Vietnam as a conceptual replication of earlier results from Germany. This study employs a regression‐based analysis of 1,010 respondents divided between a rural coastal and an urban community in Thua Thien‐Hue province. The results highlight an important set of recovery process‐related variables. The set of relevant variables is similar across genders in terms of inclusion and influence, and includes age, social capital, internal and external support after a flood, perceived severity of previous flood impacts, and the perception of stress‐resilience. However, women were affected more heavily by flooding in terms of longer recovery times, which should be accounted for in risk management. Overall, the studied variables perform similarly in Vietnam and Germany. This study, therefore, conceptually replicates previous results suggesting that women display slightly slower recovery levels as well as that psychological variables influence recovery rates more than adverse flood impacts. This provides an indication of the results' potentially robust nature due to the different socio‐environmental contexts in Germany and Vietnam.
    Keywords: 333.7 ; flood recovery ; resilience ; societal equity ; vulnerability
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    Severe thunderstorms with large hail across Germany in June 2019 (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-04-21
    Description: From 10 to 12 June 2019, severe thunderstorms affected large parts of Germany. Hail larger than golf ball size caused considerable damage, especially in the Munich area where losses amount to EUR 1 billion. This event thus ranks among the ten most expensive hail events in Europe in the last 40 years. Atmospheric blocking in combination with a moist, unstably stratified air mass provided an excellent setting for the development of severe, hail‐producing thunderstorms across the country. image
    Description: German Research Foundation http://dx.doi.org/10.13039/501100001659
    Keywords: 551.5 ; Germany ; thunderstorms ; hailstorm
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    The potential of ryegrass as cover crop to reduce soil N2O emissions and increase the population size of denitrifying bacteria (2021)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2021-07-05
    Description: Nitrogen (N) fertilization is the major contributor to nitrous oxide (N2O) emissions from agricultural soil, especially in post‐harvest seasons. This study was carried out to investigate whether ryegrass serving as cover crop affects soil N2O emissions and denitrifier community size. A microcosm experiment was conducted with soil planted with perennial ryegrass (Lolium perenne L.) and bare soil, each with four levels of N fertilizer (0, 5, 10 and 20 g N m−2; applied as calcium ammonium nitrate). The closed‐chamber approach was used to measure soil N2O fluxes. Real‐time PCR was used to estimate the biomass of bacteria and fungi and the abundance of genes involved in denitrification in soil. The results showed that the presence of ryegrass decreased the nitrate content in soil. Cumulative N2O emissions of soil with grass were lower than in bare soil at 5 and 10 g N m−2. Fertilization levels did not affect the abundance of soil bacteria and fungi. Soil with grass showed greater abundances of bacteria and fungi, as well as microorganisms carrying narG, napA, nirK, nirS and nosZ clade I genes. It is concluded that ryegrass serving as a cover crop holds the potential to mitigate soil N2O emissions in soils with moderate or high NO3− concentrations. This highlights the importance of cover crops for the reduction of N2O emissions from soil, particularly following N fertilization. Future research should explore the full potential of ryegrass to reduce soil N2O emissions under field conditions as well as in different soils. Highlights This study was to investigate whether ryegrass serving as cover crop affects soil N2O emissions and denitrifier community size; Plant reduced soil N substrates on one side, but their root exudates stimulated denitrification on the other side; N2O emissions were lower in soil with grass than bare soil at medium fertilizer levels, and growing grass stimulated the proliferation of almost all the denitrifying bacteria except nosZ clade II; Ryegrass serving as a cover crop holds the potential to mitigate soil N2O emissions.
    Description: China Scholarship Council http://dx.doi.org/10.13039/501100004543
    Description: The National Science Project for University of Anhui Province
    Keywords: 551.9 ; 631.4 ; denitrification ; perennial ryegrass (Lolium perenne L.) ; soil bacteria ; soil CO2 emissions ; soil N2O emissions
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    Pre‐instrumental summer precipitation variability in northwestern Greece from a high‐elevation Pinus heldreichii network (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-04
    Description: The spatiotemporal variability of precipitation is of vital importance to Mediterranean ecology and economy, but pre‐instrumental changes are not well understood. Here, we present a millennial‐length June–July precipitation reconstruction derived from a network of 22 Pinus heldreichii high‐elevation sites in the Pindus Mountains of northwestern Greece. Tree‐ring width chronologies from these sites cohere exceptionally well over the past several hundred years (r1467–2015 = 0.64) revealing coherence at inter‐annual to centennial timescales across the network. The network mean calibrates significantly against instrumental June–July precipitation over the past 40 years (r1976–2015 = 0.71), even though no high‐elevation observational record is available representing the moist conditions at the treeline above 1,900 m a.s.l. For the final reconstruction, the instrumental target data are adjusted to provide realistic estimates of high‐elevation summer rainfall back to 729 CE. The reconstruction contains substantially more low‐frequency variability than other high‐resolution hydroclimate records from the eastern Mediterranean including extended dry periods from 1,350 to 1,379 CE (39 ± 4.5 mm) and 913 to 942 (40 ± 8.4 mm), and moist periods from 862 to 891 (86 ± 11 mm) and 1,522 to 1,551 (80 ± 3.5 mm), relative to the long‐term mean of 61 mm. The most recent 30‐year period from 1986 to 2015 is characterized by above average June–July precipitation (73 ± 2 mm). Low‐frequency changes in summer precipitation are likely related to variations in the position and persistence of storm tracks steering local depressions and causing extensive rainfall (or lack thereof) in high‐elevation environments of the Pindus Mountains.
    Description: Associated with a strengthening of circum‐global sub‐tropical high‐pressure belts, climate models unequivocally predict a decrease of Mediterranean precipitation, accompanied by an increase of extreme events in the upcoming decades. Long‐term desiccation will amplify evaporative demand challenging plant metabolism and foster an even greater need to irrigate Mediterranean crops. We place these recent hydroclimate dynamics into a long‐term context and explore the feasibility of reconstructing low‐frequency precipitation variability by employing a large network of high‐elevation Pinus heldreichii sites from northwestern Greece.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 551.6 ; climate reconstruction ; Mediterranean ; Pindus Mountains ; pine ; tree‐rings ; Valia Calda
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    Grassland greening on the Mongolian Plateau despite higher grazing intensity (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-06-28
    Description: Changes in land management and climate alter vegetation dynamics, but the determinants of vegetation changes often remain elusive, especially in global drylands. Here we assess the determinants of grassland greenness on the Mongolian Plateau, one of the world's largest grassland biomes, which covers Mongolia and the province of Inner Mongolia in China. We use spatial panel regressions to quantify the impact of precipitation, temperature, radiation, and the intensity of livestock grazing on the normalized difference vegetation indices (NDVI) during the growing seasons from 1982 to 2015 at the county level. The results suggest that the Mongolian Plateau experienced vegetation greening from 1982 to 2015. Precipitation and animal density were the most influential factors contributing to higher NDVI on the grasslands of Inner Mongolia and Mongolia. Our results highlight the dominant effect of climate variability, and especially of the precipitation variability, on the grassland greenness in Mongolian drylands. The findings challenge the common belief that higher grazing pressure is the key driver for land degradation. The analysis exemplifies how representative wall‐to‐wall results for large areas can be attained from exploring space–time data and adds empirical insights to the puzzling relationship between grazing intensity and vegetation growth in dryland areas.
    Description: European Union's Framework Programme for Research and Innovation ‐ Horizon 2020 (2014‐2020)
    Description: Alexander von Humboldt Foundation of Germany
    Keywords: 333.7 ; China ; climate change ; grassland ; livestock grazing ; NDVI ; spatial panel regression ; vegetation growth
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    Contextualizing land‐use and land‐cover change with local knowledge: A case study from Pokot Central, Kenya (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-16
    Description: Rural communities in the drylands of sub‐Saharan Africa (SSA) derive their livelihoods primarily from their natural resource base. Unprecedented changes in these environments over the past few decades are likely to intensify in the future and land users need to develop sustainable adaptation strategies. This study aims to identify land‐use and land‐cover (LULC) changes and their drivers in a sub‐Saharan dryland, between 1986 and 2017, by integrating local knowledge and remote sensing. Local knowledge and environmental perception are used as the basis for defining LULC classes and for training and validation of change detection. This study detects significant LULC changes in 41% of the investigated area, and identifies bush encroachment into former pastures as the dominant LULC change with an increase of woodland by 39% and a decrease of grassland by 74%. This process is perceived as severe degradation by local respondents and is linked to changing management regimes and unreliable rainfall patterns. Deforestation and woodland thinning account for 44% of the detected changes, and can be traced back to increased habitation and farming, although the local community also identifies charcoal production as a driving factor. The integration of remote sensing and local knowledge provides a holistic view on LULC change in Pokot Central, Kenya and offers a solid base for site‐specific and actor‐centred management approaches necessary for sustainable pathways of drylands. Our results emphasize the need to include local actors in the development of adaptation strategies and management guidelines for drylands.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Heidelberg University, Graduiertenförderung
    Keywords: 631.37 ; Kenya ; LANDSAT ; land‐use and land‐cover change ; local knowledge ; Pokot Central ; remote sensing
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    Comprehensive evaluation of an improved large‐scale multi‐site weather generator for Germany (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-06-29
    Description: In this work, we present a comprehensive evaluation of a stochastic multi‐site, multi‐variate weather generator at the scale of entire Germany and parts of the neighbouring countries covering the major German river basins Elbe, Upper Danube, Rhine, Weser and Ems with a total area of approximately 580,000 km2. The regional weather generator, which is based on a first‐order multi‐variate auto‐regressive model, is setup using 53‐year long daily observational data at 528 locations. The performance is evaluated by investigating the ability of the weather generator to replicate various important statistical properties of the observed variables including precipitation occurrence and dry/wet transition probabilities, mean daily and extreme precipitation, multi‐day precipitation sums, spatial correlation structure, areal precipitation, mean daily and extreme temperature and solar radiation. We explore two marginal distributions for daily precipitation amount: mixed Gamma‐Generalized Pareto and extended Generalized Pareto. Furthermore, we introduce a new procedure to estimate the spatial correlation matrix and model mean daily temperature and solar radiation. The extensive evaluation reveals that the weather generator is greatly capable of capturing most of the crucial properties of the weather variables, particularly of extreme precipitation at individual locations. Some deficiencies are detected in capturing spatial precipitation correlation structure that leads to an overestimation of areal precipitation extremes. Further improvement of the spatial correlation structure is envisaged for future research. The mixed marginal model found to outperform the extended Generalized Pareto in our case. The use of power transformation in combination with normal distribution significantly improves the performance for non‐precipitation variables. The weather generator can be used to generate synthetic event footprints for large‐scale trans‐basin flood risk assessment.
    Description: The regional weather generator is greatly capable of capturing most of the crucial statistical properties of weather events. Hence, it can be used to generate synthetic event footprints for large‐scale trans‐basin flood risk assessment. However, due to its deficiency in capturing spatial precipitation correlation structure leading to an overestimation of areal precipitation extremes, further improvement is envisaged for future research.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 551.6 ; correlation ; extreme ; flood ; large‐scale ; multi‐variate ; weather generator
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    ogs5py: A Python‐API for the OpenGeoSys 5 Scientific Modeling Package (2021)
    Blackwell Publishing Ltd | Malden, US
    Details
    Publication Date: 2021-07-04
    Description: High‐performance numerical codes are an indispensable tool for hydrogeologists when modeling subsurface flow and transport systems. But as they are written in compiled languages, like C/C++ or Fortran, established software packages are rarely user‐friendly, limiting a wider adoption of such tools. OpenGeoSys (OGS), an open‐source, finite‐element solver for thermo‐hydro‐mechanical–chemical processes in porous and fractured media, is no exception. Graphical user interfaces may increase usability, but do so at a dramatic reduction of flexibility and are difficult or impossible to integrate into a larger workflow. Python offers an optimal trade‐off between these goals by providing a highly flexible, yet comparatively user‐friendly environment for software applications. Hence, we introduce ogs5py, a Python‐API for the OpenGeoSys 5 scientific modeling package. It provides a fully Python‐based representation of an OGS project, a large array of convenience functions for users to interact with OGS and connects OGS to the scientific and computational environment of Python.
    Description: German Federal Environmental Foundation http://dx.doi.org/10.13039/100007636
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 551.49 ; hydrogeology ; subsurface flow ; modeling ; software
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    High‐Resolution Integrated Transport Model for Studying Surface Water–Groundwater Interaction (2021)
    Blackwell Publishing Ltd | Malden, US
    Details
    Publication Date: 2021-06-27
    Description: Transport processes that lead to exchange of mass between surface water and groundwater play a significant role for the ecological functioning of aquatic systems, for hydrological processes and for biogeochemical transformations. In this study, we present a novel integral modeling approach for flow and transport at the sediment–water interface. The model allows us to simultaneously simulate turbulent surface and subsurface flow and transport with the same conceptual approach. For this purpose, a conservative transport equation was implemented to an existing approach that uses an extended version of the Navier–Stokes equations. Based on previous flume studies which investigated the spreading of a dye tracer under neutral, losing and gaining flow conditions the new solver is validated. Tracer distributions of the experiments are in close agreement with the simulations. The simulated flow paths are significantly affected by in‐ and outflowing groundwater flow. The highest velocities within the sediment are found for losing condition, which leads to shorter residence times compared to neutral and gaining conditions. The largest extent of the hyporheic exchange flow is observed under neutral condition. The new solver can be used for further examinations of cases that are not suitable for the conventional coupled models, for example, if Reynolds numbers are larger than 10. Moreover, results gained with the integral solver provide high‐resolution information on pressure and velocity distributions at the rippled streambed, which can be used to improve flow predictions. This includes the extent of hyporheic exchange under varying ambient groundwater flow conditions.
    Description: Technische Universität Berlin, Germany
    Description: German Research Foundation http://dx.doi.org/10.13039/501100001659
    Keywords: 551.4 ; aquatic systems ; sediment-water interface ; transport model
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    The regional MiKlip decadal prediction system for Europe: Hindcast skill for extremes and user‐oriented variables (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-03
    Description: Regional climate predictions for the next decade are gaining importance, as this period falls within the planning horizon of politics, economy, and society. The potential predictability of climate indices or extremes at the regional scale is of particular interest. The German MiKlip project (“mid‐term climate forecast”) developed the first regional decadal prediction system for Europe at 0.44° resolution, based on the regional model COSMO‐CLM using global MPI‐ESM simulations as boundary conditions. We analyse the skill of this regional system focussing on extremes and user‐oriented variables. The considered quantities are related to temperature extremes, heavy precipitation, wind impacts, and the agronomy sector. Variables related to temperature (e.g., frost days, heat wave days) show high predictive skill (anomaly correlation up to 0.9) with very little dependence on lead‐time, and the skill patterns are spatially robust. The skill patterns for precipitation‐related variables (e.g., heavy precipitation days) and wind‐based indices (like storm days) are less skilful and more heterogeneous, particularly for the latter. Quantities related to the agronomy sector (e.g., growing degree days) show high predictive skill, comparable to temperature. Overall, we provide evidence that decadal predictive skill can be generally found at the regional scale also for extremes and user‐oriented variables, demonstrating how the utility of decadal predictions can be substantially enhanced. This is a very promising first step towards impact‐related modelling at the regional scale and the development of individual user‐oriented products for stakeholders.
    Description: The skill of the regional MiKlip decadal prediction system is analysed focussing on extremes and user‐oriented variables. Variables related to temperature extremes and the agronomy sector show high predictive skill with very little dependence on lead‐time. Skill patterns for precipitation‐related variables and wind‐based indices are less skilful and more heterogeneous, especially for the latter.
    Description: The study was mainly funded by the Bundesministerium für Bildung und Forschung (BMBF) under project FONA MiKlip‐II http://dx.doi.org/10.13039/501100002347
    Description: AXA Research Fund http://dx.doi.org/10.13039/501100001961
    Keywords: 551.6 ; climate services ; Europe ; extremes ; MiKlip ; regional decadal predictions ; user needs
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    Assessing land use and flood management impacts on ecosystem services in a river landscape (Upper Danube, Germany) (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-06-28
    Description: Rivers and floodplains provide many regulating, provisioning and cultural ecosystem services (ES) such as flood risk regulation, crop production or recreation. Intensive use of resources such as hydropower production, construction of detention basins and intensive agriculture substantially change ecosystems and may affect their capacity to provide ES. Legal frameworks such as the European Water Framework Directive, Bird and Habitats Directive and Floods Directive already address various uses and interests. However, management is still sectoral and often potential synergies or trade‐offs between sectors are not considered. The ES concept could support a joint and holistic evaluation of impacts and proactively suggest advantageous options. The river ecosystem service index (RESI) method evaluates the capacity of floodplains to provide ES by using a standardized five‐point scale for 1 km‐floodplain segments based on available spatial data. This scaling allows consistent scoring of all ES and their integration into a single index. The aim of this article is to assess ES impacts of different flood prevention scenarios on a 75 km section of the Danube river corridor in Germany. The RESI method was applied to evaluate scenario effects on 13 ES with the standardized five‐point scale. Synergies and trade‐offs were identified as well as ES bundles and dependencies on land use and connectivity. The ratio of actual and former floodplain has the strongest influence on the total ES provision: the higher the percentage and area of an active floodplain, the higher the sum of ES. The RESI method proved useful to support decision‐making in regional planning.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Keywords: 333.91 ; assessment ; cultural ; floodplains ; index ; inter‐sectoral management ; regulating and provisioning ecosystem services ; stakeholders
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    Iron isotope fractionation in soil and graminaceous crops after 100 years of liming in the long‐term agricultural experimental site at Berlin‐Dahlem, Germany (2021)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2021-07-05
    Description: Sustainable arable cropping relies on repeated liming. Yet, the associated increase in soil pH can reduce the availability of iron (Fe) to plants. We hypothesized that repeated liming, but not pedogenic processes such as lessivage (i.e., translocation of clay particles), alters the Fe cycle in Luvisol soil, thereby affecting Fe isotope composition in soils and crops. Hence, we analysed Fe concentrations and isotope compositions in soil profiles and winter rye from the long‐term agricultural experimental site in Berlin‐Dahlem, Germany, where a controlled liming trial with three field replicates per treatment has been conducted on Albic Luvisols since 1923. Heterogeneity in subsoil was observed at this site for Fe concentration but not for Fe isotope composition. Lessivage had not affected Fe isotope composition in the soil profiles. The results also showed that almost 100 years of liming lowered the concentration of the HCl‐extractable Fe that was potentially available for plant uptake in the surface soil (0–15 cm) from 1.03 (standard error (SE) 0.03) to 0.94 (SE 0.01) g kg−1. This HCl‐extractable Fe pool contained isotopically lighter Fe (δ56Fe = −0.05 to −0.29‰) than the bulk soil (δ56Fe = −0.08 to 0.08‰). However, its Fe isotope composition was not altered by the long‐term lime application. Liming resulted in relatively lower Fe concentrations in the roots of winter rye. In addition, liming led to a heavier Fe isotope composition of the whole plants compared with those grown in the non‐limed plots (δ56FeWholePlant_ + Lime = −0.12‰, SE 0.03 vs. δ56FeWholePlant_‐Lime = −0.21‰, SE 0.01). This suggests that the elevated soil pH (increased by one unit due to liming) promoted the Fe uptake strategy through complexation of Fe(III) from the rhizosphere, which favoured heavier Fe isotopes. Overall, the present study showed that liming and a related increase in pH did not affect the Fe isotope compositions of the soil, but may influence the Fe isotope composition of plants grown in the soil if they alter their Fe uptake strategy upon the change of Fe availability. Highlights Fe concentrations and stocks, but not Fe isotope compositions, were more heterogeneous in subsoil than in topsoil. Translocation of clay minerals did not result in Fe isotope fractionation in the soil profile of a Luvisol. Liming decreased Fe availability in topsoil, but did not affect its δ56Fe values. Uptake of heavier Fe isotopes by graminaceous crops was more pronounced at elevated pH.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Keywords: 551.9 ; liming ; plant‐available Fe pool in soil ; winter rye ; δ56Fe
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    Nonstationarity of the link between the Tropics and the summer East Atlantic pattern (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-03
    Description: A 700‐year pre‐industrial control run with the MPI‐ESM‐LR model is used to investigate the link between the summer East Atlantic (SEA) pattern and the Pacific‐Caribbean rainfall dipole (PCD), a link that has previously been shown using ERA‐Interim reanalysis data. In the model, it is found that the link between the SEA and PCD is present in some multidecadal epochs but not in others. A simple statistical model reproduces this behaviour. In the statistical model, the SEA is represented by a white noise process plus a weak influence from the PCD based on the full 700 years of the model run. The statistical model is relevant to other extratropical modes of variability, for example, the winter North Atlantic Oscillation (NAO), that are weakly influenced by the Tropics. It follows that the link between the Tropics and the winter NAO is likely to undergo modulation on multidecadal time scales, as found in some previous studies. The results suggest that any predictability of the SEA, and by implication the NAO, based on tropical rainfall may not be robust and may, in fact, be modulated on multidecadal time scales, with implications for seasonal and decadal prediction systems.
    Description: The positive phase of the SEA is associated with warm summers in Europe. The figure shows the running correlation in 51 year windows between the SEA index and the corresponding tropical rainfall index in a long pre‐industrial model run. The link between tropical rainfall and the SEA exists only in some decadal epochs, shown by the green shading, implying that predictability of the SEA based on tropical rainfall can be expected to vary on multidecadal time scales.
    Keywords: 551.5 ; nonstationarity ; seasonal prediction ; summer East Atlantic pattern
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    Convective rain cell characteristics and scaling in climate projections for Germany (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-03
    Description: Extreme convective precipitation is expected to increase with global warming. However, the rate of increase and the understanding of contributing processes remain highly uncertain. We investigated characteristics of convective rain cells like area, intensity, and lifetime as simulated by a convection‐permitting climate model in the area of Germany under historical (1976–2005) and future (end‐of‐century, RCP8.5 scenario) conditions. To this end, a tracking algorithm was applied to 5‐min precipitation output. While the number of convective cells is virtually similar under historical and future conditions, there are more intense and larger cells in the future. This yields an increase in hourly precipitation extremes, although mean precipitation decreases. The relative change in the frequency distributions of area, intensity, and precipitation sum per cell is highest for the most extreme percentiles, suggesting that extreme events intensify the most. Furthermore, we investigated the temperature and moisture scaling of cell characteristics. The temperature scaling drops off at high temperatures, with a shift in drop‐off towards higher temperatures in the future, allowing for higher peak values. In contrast, dew point temperature scaling shows consistent rates across the whole dew point range. Cell characteristics scale at varying rates, either below (mean intensity), at about (maximum intensity and area), or above (precipitation sum) the Clausius–Clapeyron rate. Thus, the widely investigated extreme precipitation scaling at fixed locations is a complex product of the scaling of different cell characteristics. The dew point scaling rates and absolute values of the scaling curves in historical and future conditions are closest for the highest percentiles. Therefore, near‐surface humidity provides a good predictor for the upper limit of for example, maximum intensity and total precipitation of individual convective cells. However, the frequency distribution of the number of cells depending on dew point temperature changes in the future, preventing statistical inference of extreme precipitation from near‐surface humidity.
    Description: We investigated characteristics of convective rain cells under historical and future conditions in convection‐permitting climate simulations using a tracking algorithm. There are more intense and larger cells in the future yielding an increase in hourly precipitation extremes. The temperature scaling curves of cell characteristics shift towards higher peak values at higher temperatures in the future. In contrast, cell characteristics scale consistently with dew point temperature. Therefore, near‐surface humidity provides a good predictor for the upper limit of for example, maximum intensity, and total precipitation of convective cells.
    Keywords: 551.6 ; Clausius–Clapeyron scaling ; convection‐permitting simulation ; convective storms ; COSMO‐CLM ; precipitation ; tracking
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    Habitat availability determines food chain length and interaction strength in food webs of a large lowland river (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-04-07
    Description: Many large rivers used for navigation have lost their hydromorphological heterogeneity, which has led to the widespread loss of native biodiversity and the concurrent establishment of non‐native communities. While the effects on biodiversity are well‐described, we know little about how the loss of natural habitats and the restructuring of communities cumulate into effects on riverine food webs. We constructed binary and ingestion webs for benthic macroinvertebrates and their resources in the Elbe River (Germany) and compared if food chain length, food web complexity, robustness, ingestion rates, and consumer‐resource interaction strength differ among three shoreline engineering practices. Food webs at profoundly altered shorelines were significantly less complex and had significantly shorter food chains than the food web at the semi‐natural shoreline. However, food web robustness to a simulated loss of species was comparable at all shorelines. Total ingestion rates were up to eight times lower at highly altered shorelines due to significantly lower ingestion rates by native species. Predator–prey interaction strength was comparable among shorelines due to higher shares of non‐native predators, indicating that non‐native predators can be functionally equivalent to native predators. We attributed the observed food web differences to the absence of complex habitats at profoundly altered shorelines and the accompanied absence of specialized consumers. Our study provides empirical evidence that hydromorphological modifications reduce the efficiency of food webs to control organic matter dynamics and may ultimately affect the provisioning of riverine ecosystem services.
    Keywords: ddc:339.95 ; ddc:551.483
    Language: English
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    Adoption of multiple sustainable land management practices among irrigator rural farm households of Ethiopia (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-04-01
    Description: Using a household and plot‐level survey conducted in Ethiopia, this study analyses the difference in farmers' adoption of sustainable land management (SLM) practices between their rainfed and irrigated plots. The paper also investigates the varying influence of different types of irrigation water management systems and associated irrigation technologies on the adoption of SLM practices in irrigated plots. After controlling for heterogeneity among different irrigation water management systems and technologies, we found that access to irrigation play major role in enhancing farmers' motivation to adopt more SLM practices. Furthermore, the combined effect of irrigation water management system and irrigation technology on type and number of SLM practices adopted is quite varied and very significant. The evidence highlights that farmers adopt more SLM practices in their plots with pump irrigation compared with those plots where gravity irrigation is applied because pump irrigation systems enhance complementarities with SLM practices. Finally, the findings underscore that the type of irrigation water management and the irrigation technology applied play an important role in restoring degraded lands and maintaining soil fertility, even when farmers' adoption of irrigation was not explicitly triggered by concerns for soil health.
    Description: Center for Development Research (ZEF), University of Bonn
    Description: CGIAR Research Program on Water, Land, and Ecosystems
    Description: Deutscher Akademischer Austauschdienst (DAAD) http://dx.doi.org/10.13039/501100001655
    Description: Dr. Hermann Eiselen Doctoral Program of the Foundation Fiat
    Description: Federal Ministry for Economic Cooperation and Development (BMZ) of Germany, The Water‐Energy‐Food Nexus: Global, Basin and Local Case Studies of Resource Use Efficiency Under Growing Natural Resource Scarcity
    Keywords: ddc:631
    Language: English
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    How to Find Aquifer Statistics Utilizing Pumping Tests? Two Field Studies Using welltestpy (2021)
    Blackwell Publishing Ltd | Malden, US
    Details
    Publication Date: 2022-04-01
    Description: We present a workflow to estimate geostatistical aquifer parameters from pumping test data using the Python package welltestpy. The procedure of pumping test analysis is exemplified for two data sets from the Horkheimer Insel site and from the Lauswiesen site, Germany. The analysis is based on a semi‐analytical drawdown solution from the upscaling approach Radial Coarse Graining, which enables to infer log‐transmissivity variance and horizontal correlation length, beside mean transmissivity, and storativity, from pumping test data. We estimate these parameters of aquifer heterogeneity from type‐curve analysis and determine their sensitivity. This procedure, implemented in welltestpy, is a template for analyzing any pumping test. It goes beyond the possibilities of standard methods, for example, based on Theis' equation, which are limited to mean transmissivity and storativity. A sensitivity study showed the impact of observation well positions on the parameter estimation quality. The insights of this study help to optimize future test setups for geostatistical aquifer analysis and provides guidance for investigating pumping tests with regard to aquifer statistics using the open‐source software package welltestpy.
    Description: Article impact statement: We present a workflow to infer parameters of subsurface heterogeneity from pumping test data exemplified at two sites using welltestpy.
    Description: German Federal Environmental Foundation (DBU) http://dx.doi.org/10.13039/100007636
    Keywords: ddc:551.49
    Language: English
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    The HydroEcoSedimentary tool: An integrated approach to characterise interstitial hydro‐sedimentary and associated ecological processes (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-04-01
    Description: Increased deposition of fine sediments in rivers and streams affects a range of key ecosystem processes across the sediment–water interface, and it is a critical aspect of river habitat degradation and restoration. Understanding the mechanisms leading to fine sediment accumulation along and across streambeds and their effect on ecological processes is essential for comprehending human impacts on river ecosystems and informing river restoration. Here, we introduce the HydroEcoSedimentary tool (HEST) as an integrated approach to assess hydro‐sedimentary and ecologically relevant processes together. The HEST integrates the estimation of sedimentary processes in the interstitial zone, as well as hydraulic, geochemical and ecological assessments, with a focus on brown trout early life stages. Compared to other methods, the HEST expands the possibilities to monitor and quantify fine sediment deposition in streambeds by differentiating between vertical, lateral and longitudinal infiltration pathways, and distinguishing between the depth (upper vs. lower layers) at which interstitial processes occur within the sediment column. By testing the method in two rivers with different degrees of morphological degradation, we detail the possible measurements and uses of the HEST, demonstrate its feasibility and discuss its reliability.
    Description: Alexander von Humboldt‐Stiftung http://dx.doi.org/10.13039/100005156
    Description: Bavarian State Ministry of Science and Arts (Bayerisches Staatsministerium für Wissenschaft und Kunst)
    Keywords: ddc:551.48 ; ddc:550.724
    Language: English
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    The effect of stream shading on the inflow characteristics in a downstream reservoir (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-04-01
    Description: In thermally stratified reservoirs, inflows form density currents according to the interplay between inflow temperature and reservoir stratification. The temperature of inflowing water is affected by catchment properties, including shading by riparian vegetation. We hypothesize that the degree of shading in the catchment can affect the inflow dynamics in downstream reservoirs by changing inflow temperature and consequently the nature of the density current. We test it for a subtropical drinking water reservoir by combining catchment‐scale hydrological and stream temperature modeling with observations of reservoir stratification. We analyze the formation of density currents, defined as under, inter and overflow, for scenarios with contrasting shading conditions in the catchment. Inflow temperatures were simulated with the distributed water‐balance model LARSIM‐WT, which integrates heat‐balance and water temperature. River temperature measurements and simulations are in good agreement with a RMSE of 0.58°C. In simulations using the present state of shading, underflows are the most frequent flow path, 63% of the annual period. During the remaining time, river intrusion form interflows. In a scenario without stream shading, average inflow temperature increased by 2.2°C. Thus, interflows were the most frequent flow path (51%), followed by underflows (34%) and overflows (15%). With this change, we would expect a degradation of reservoir water quality, as overflows promote longer periods of anoxia and nutrient loads would be delivered to the photic zone, a potential trigger for algae blooms. This study revealed a potentially important, yet unexplored aspect of catchment management for controlling reservoir water quality.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: https://doi.org/10.5281/zenodo.4746288
    Keywords: ddc:628.1 ; ddc:551.48
    Language: English
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    Impact of a large artificial lake on regional climate: A typical meteorological year Meso‐NH simulation results (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-04-01
    Description: Large artificial lakes and reservoirs affect the meteorological regime of the shore area and the local climate takes on a number of new features that were previously absent. This work focuses on the weather impact of the Alqueva reservoir, the largest artificial lake in Western Europe. An extensive set of numerical simulations using Meso‐NH mesoscale atmospheric model coupled with FLake (Freshwater Lake) scheme was carried out. The simulations covered a 12‐month period that was chosen to compose a so‐called Typical Meteorological Year. This artificial time period is meant to represent the typical meteorological conditions in the region and the model results are used to assess the changes in the local climate. To evaluate the raw impact of the reservoir, two different scenarios of simulations were compared: (A) with the reservoir as it exists nowadays and (B) without the reservoir using the older surface dataset. The results show decrease of air temperature during daytime (10–9°C) and nighttime increase (up to 10°C). In nearest towns, daily maximum temperature decreased and daily minimum temperature increased, which refers to milder weather conditions. Alqueva mainly showed suppression in fog formation in the nearby area. Local breeze regime was studied and monthly lake/land breezes were described.
    Description: Large lakes and artificial reservoirs can affect the meteorological regime of their coastal areas and impact the local climate. This work focuses on the weather impact of the Alqueva reservoir, the largest artificial lake in Western Europe, studied on the basis of mesoscale atmospheric modelling data over the 12‐month period composed in a typical meteorological year for the region of interest.
    Description: ALOP project
    Description: COMPETE 2020 ICT project
    Description: Fundação para a Ciência e a Tecnologia http://dx.doi.org/10.13039/501100001871
    Description: TOMAQAPA
    Description: http://mesonh.aero.obs-mip.fr/mesonh54/Download
    Keywords: ddc:551.6
    Language: English
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    Importance of sources of variability, scales and experimental design: A case study about the effects of biochar and slurry application on soil properties in agricultural silty loam soils (2021)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2022-04-01
    Description: In designed experiments, different sources of variability and an adequate scale of measurement need to be considered, but not all approaches in common usage are equally valid. In order to elucidate the importance of sources of variability and choice of scale, we conducted an experiment where the effects of biochar and slurry applications on soil properties related to soil fertility were studied for different designs: (a) for a field‐scale sampling design with either a model soil (without natural variability) as an internal control or with composited soils, (b) for a design with a focus on amendment variabilities, and (c) for three individual field‐scale designs with true field replication and a combined analysis representative of the population of loess‐derived soils. Three silty loam sites in Germany were sampled and the soil macroaggregates were crushed. For each design, six treatments (0, 0.15 and 0.30 g slurry‐N kg−1 with and without 30 g biochar kg−1) were applied before incubating the units under constant soil moisture conditions for 78 days. CO2 fluxes were monitored and soils were analysed for macroaggregate yields and associated organic carbon (C). Mixed‐effects models were used to describe the effects. For all soil properties, results for the loess sites differed with respect to significant contributions of fixed effects for at least one site, suggesting the need for a general inclusion of different sites. Analysis using a multilevel model allowed generalizations for loess soils to be made and showed that site:slurry:biochar and site:slurry interactions were not negligible for macroaggregate yields. The use of a model soil as an internal control enabled observation of variabilities other than those related to soils or amendments. Experiments incorporating natural variability in soils or amendments resulted in partially different outcomes, indicating the need to include all important sources of variability. Highlights Effects of biochar and slurry applications were studied for different designs and mixed‐effects models were used to describe the effects. Including an internal control allowed observation of, e.g., methodological and analytical variabilities. The results suggested the need for a general inclusion of different sites. Analysis using a multilevel model allowed generalizations for loess soils. The results indicated the need to include all important sources of variability.
    Keywords: ddc:631.4
    Language: English
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    Do tree species affect decadal changes in soil organic carbon and total nitrogen stocks in Danish common garden experiments? (2021)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2022-04-01
    Description: Temperate forest soils are often considered as an important sink for atmospheric carbon (C), thereby buffering anthropogenic CO2 emissions. However, the effect of tree species composition on the magnitude of this sink is unclear. We resampled a tree species common garden experiment (six sites) a decade after initial sampling to evaluate whether forest floor (FF) and topsoil organic carbon (Corg) and total nitrogen (Nt) stocks changed in dependence of tree species (Norway spruce—Picea abies L., European beech—Fagus sylvatica L., pedunculate oak—Quercus robur L., sycamore maple—Acer pseudoplatanus L., European ash—Fraxinus excelsior L. and small‐leaved lime—Tilia cordata L.). Two groups of species were identified in terms of Corg and Nt distribution: (1) Spruce with high Corg and Nt stocks in the FF developed as a mor humus layer which tended to have smaller Corg and Nt stocks and a wider Corg:Nt ratio in the mineral topsoil, and (2) the broadleaved species, of which ash and maple distinguished most clearly from spruce by very low Corg and Nt stocks in the FF developed as mull humus layer, had greater Corg and Nt stocks, and narrow Corg:Nt ratios in the mineral topsoil. Over 11 years, FF Corg and Nt stocks increased most under spruce, while small decreases in bulk mineral soil (esp. in 0–15 cm and 0–30 cm depth) Corg and Nt stocks dominated irrespective of species. Observed decadal changes were associated with site‐related and tree species‐mediated soil properties in a way that hinted towards short‐term accumulation and mineralisation dynamics of easily available organic substances. We found no indication for Corg stabilisation. However, results indicated increasing Nt stabilisation with increasing biomass of burrowing earthworms, which were highest under ash, lime and maple and lowest under spruce. Highlights We studied if tree species differences in topsoil Corg and Nt stocks substantiate after a decade. The study is unique in its repeated soil sampling in a multisite common garden experiment. Forest floors increased under spruce, but topsoil stocks decreased irrespective of species. Changes were of short‐term nature. Nitrogen was most stable under arbuscular mycorrhizal species.
    Description: Deutsche Forschungsgemeinschaff (DFG)
    Keywords: ddc:551.9 ; ddc:631.41
    Language: English
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    Targeted covariance inflation for 3D‐volume radar reflectivity assimilation with the LETKF (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-03-31
    Description: The local ensemble transform Kalman filter (LETKF) suggested by Hunt et al., 2007 is a very popular method for ensemble data assimilation. It is the operational method for convective‐scale data assimilation at Deutscher Wetterdienst (DWD). At DWD, based on the LETKF, three‐dimensional volume radar observations are assimilated operationally for the operational ICON‐D2. However, one major challenge for the LETKF is the situation where observations show precipitation (reflectivity) whereas all ensemble members do not show such reflectivity at a given point in space. In this case, there is no sensitivity of the LETKF with respect to the observations, and the analysis increment based on the observed reflectivity is zero. The goal of this work is to develop a targeted covariance inflation (TCI) for the assimilation of 3D‐volume radar data based on the LETKF, adding artificial sensitivity and making the LETKF react properly to the radar observations. The basic idea of the TCI is to employ an additive covariance inflation as entrance point for the LETKF. Here, we construct perturbations to the simulated observation which are used by the core LETKF assimilation step. The perturbations are constructed such that they exhibit a correlation between humidity and reflectivity. This leads to a change in humidity in such a way that precipitation is more likely to occur. We describe and demonstrate the theoretical basis of the method. We then present a case study where targeted covariance inflation leads to a clear improvement of the LETKF and precipitation forecast. All examples are based on the German radar network and the ICON‐D2 model over Central Europe.
    Description: The goal of this work is to develop a targeted covariance inflation (TCI) for the assimilation of 3D‐volume radar data based on the local ensemble transform Kalman filter (LETKF), adding artificial sensitivity and making the LETKF react properly to the radar observations. Perturbations to the simulated observations are constructed such that they exhibit an empirically derived correlation between humidity and reflectivity. This leads to a change in humidity in such a way that precipitation is more likely to occur.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.5
    Language: English
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    Multi‐objective downscaling of precipitation time series by genetic programming (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
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    Publication Date: 2022-03-28
    Description: We use symbolic regression to estimate daily precipitation amounts at six stations in the Alpine region from a global reanalysis. Symbolic regression only prescribes the set of mathematical expressions allowed in the regression model, but not its structure. The regression models are generated by genetic programming (GP) in analogy to biological evolution. The two conflicting objectives of a low root‐mean‐square error (RMSE) and consistency in the distribution between model and observations are treated as a multi‐objective optimization problem. This allows us to derive a set of downscaling models that represents different achievable trade‐offs between the two conflicting objectives, a so‐called Pareto set. Our GP setup limits the size of the regression models and uses an analytical quotient instead of a standard or protected division operator. With this setup we obtain models that have a generalization performance comparable with generalized linear regression models (GLMs), which are used as a benchmark. We generate deterministic and stochastic downscaling models with GP. The deterministic downscaling models with low RMSE outperform the respective stochastic models. The stochastic models with low IQD, however, perform slightly better than the respective deterministic models for the majority of cases. No approach is uniquely superior. The stochastic models with optimal IQD provide useful distribution estimates that capture the stochastic uncertainty similar to or slightly better than the GLM‐based downscaling.
    Description: We have fitted deterministic and stochastic empirical‐statistical downscaling models that represent different possible compromises between two conflicting objectives: (a) a low RMSE and (b) consistency in the distribution between downscaled series and reference observations. The graphic shows the skill of our downscaling models w.r.t. the two objectives (larger is better) for the station Sonnblick.
    Description: CRC/TR32: Patterns in Soil‐Vegetation‐Atmosphere Systems: Monitoring, Modelling and Data Assimilation; funded by the German Research Foundation (Deutsche Forschungsgemeinschaft DFG) http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.577 ; ddc:550.2
    Language: English
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    The ‘Flood Resilience Rose’: A management tool to promote transformation towards flood resilience (2021)
    Blackwell Publishing Ltd | Oxford, UK
    Details
    Publication Date: 2021-09-29
    Description: Coping with the growing impacts of flooding in EU countries, a paradigm shift in flood management can be observed, moving from safety‐based towards risk‐based approaches and holistic perspectives. Flood resilience is a common denominator of most of the approaches. In this article, we present the ‘Flood Resilience Rose’ (FRR), a management tool to promote harmonised action towards flood resilience in European regions and beyond. The FRR is a result of a two‐step process. First, based on scientific concepts as well as analysis of relevant policy documents, we identified three ‘levels of operation’. The first level refers to the EU Floods Directive and an extended multi‐layer safety approach, comprising the four different layers of protection, prevention, preparedness and recovery, and related measures to be taken. This level is not independent but depends both on the institutional (second level) and the wider (third level) context. Second, we used surveys, semi‐structured interviews and group discussions during workshops with experts from Belgium, Denmark, Germany, the Netherlands and the United Kingdom to validate the definitions and the FRR's practical relevance. The presented FRR is thus the result of rigorous theoretical and practical consideration and provides a tool capable to strengthen flood risk management practice.
    Description: European Regional Development Fund http://dx.doi.org/10.13039/501100008530
    Keywords: 551.48 ; flood defence measures ; governance and institutions ; integrated flood risk management ; resilience
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    Tillage erosion as an important driver of in‐field biomass patterns in an intensively used hummocky landscape (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-10-06
    Description: Tillage erosion causes substantial soil redistribution that can exceed water erosion especially in hummocky landscapes under highly mechanized large field agriculture. Consequently, truncated soil profiles can be found on hill shoulders and top slopes, whereas colluvial material is accumulated at footslopes, in depressions, and along downslope field borders. We tested the hypothesis that soil erosion substantially affects in‐field patterns of the enhanced vegetation index (EVI) of different crop types on landscape scale. The interrelation between the EVI (RAPIDEYE satellite data; 5 m spatial resolution) as a proxy for crop biomass and modeled total soil erosion (tillage and water erosion modeled using SPEROS‐C) was analyzed for the Quillow catchment (size: 196 km2) in Northeast Germany in a wet versus normal year for four crop types (winter wheat, maize, winter rapeseed, winter barley). Our findings clearly indicate that eroded areas had the lowest EVI values, while the highest EVI values were found in depositional areas. The differences in the EVI between erosional and depositional sites are more pronounced in the analyzed normal year. The net effect of total erosion on the EVI compared to areas without pronounced erosion or deposition ranged from −10.2% for maize in the normal year to +3.7% for winter barley in the wet year. Tillage erosion has been identified as an important driver of soil degradation affecting in‐field crop biomass patterns in a hummocky ground moraine landscape. While soil erosion estimates are to be made, more attention should be given toward tillage erosion.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 631.4 ; agroscapelab Quillow ; crop biomass patterns ; EVI ; remote sensing ; tillage erosion
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    Sensitivity to changes in the surface‐layer turbulence parameterization for stable conditions in winter: A case study with a regional climate model over the Arctic (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-03-23
    Description: The modeling of the atmospheric boundary layer over sea ice is still challenging because of the complex interaction between clouds, radiation and turbulence over the often inhomogeneous sea ice cover. There is still much uncertainty concerning sea ice roughness, near‐surface thermal stability and related processes, and their accurate parameterization. Here, a regional Arctic climate model forced by ERA‐Interim data was used to test the sensitivity of climate simulations to a modified surface flux parameterization for wintertime conditions over the Arctic. The reference parameterization as well as the modified one is based on Monin–Obukhov similarity theory, but different roughness lengths were prescribed and the stability dependence of the transfer coefficients for momentum, heat and moisture differed from each other. The modified parameterization accounts for the most comprehensive observations that are presently available over sea ice in the inner Arctic. Independent of the parameterization used, the model was able to reproduce the two observed dominant winter states with respect to cloud cover and longwave radiation. A stepwise use of the different parameterization assumptions showed that modifications of both surface roughness and stability dependence had a considerable impact on quantities such as air pressure, wind and near‐surface turbulent fluxes. However, the reduction of surface roughness to values agreeing with those observed during the Surface Heat Budget of the Arctic Ocean campaign led to an improvement in the western Arctic, while the modified stability parameterization had only a minor impact. The latter could be traced back to the model's underestimation of the strength of stability over sea ice. Future work should concentrate on possible reasons for this underestimation and on the question of generality of the results for other climate models.
    Description: The modeling of the atmospheric boundary layer over sea ice is challenging. This is, among others, due to the distinct sea ice surface roughness and pressure ridges as shown in the image, and the often stably stratified atmosphere. We quantified the impact of used parameterizations and show that both surface roughness and stability dependence have a considerable impact on near‐surface turbulent fluxes and atmospheric circulation in Arctic climate simulations.
    Description: German Research Foundation (DFG)
    Description: Helmholtz Association (HGF), POLEX http://dx.doi.org/10.13039/100003872
    Description: Russian Science Foundation (RSF) http://dx.doi.org/10.13039/501100006769
    Keywords: ddc:551.5
    Language: English
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    Variability of the precipitation over the Tianshan Mountains, Central Asia. Part I: Linear and nonlinear trends of the annual and seasonal precipitation (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-03-29
    Description: The Tianshan Mountains, with their status as ‘water tower’, receive quantities of precipitation that are among the highest in Central Asia. There are considerable knowledge gaps regarding the understanding of spatial and temporal patterns of precipitation over this water‐scarce region. Based on the Global Precipitation Climatology Centre (GPCC) data set, this study evaluated the precipitation variations over Tianshan Mountains on different time scales by using Mann‐Kendall (M‐K) test approaches and the ensemble empirical mode decomposition (EEMD) method. The results show that (a) most parts of Tianshan experienced increasing annual precipitation during 1950–2016 while Western Tianshan, which is the wettest region, faced a downtrend of precipitation during the same 67 years; (b) the annual precipitation in the Tianshan Mountains has exhibited high‐frequency variations with 3‐ and 6‐year quasi‐periods and low‐frequency variations with 12‐, 27‐year quasi‐periods. On the decadal scale, Tianshan had two dry periods (1950–1962 and 1973–1984) and two wet periods (1962–1972 and 1985–2016) and has experienced a tendency of continuous humidification since 2004; (c) the precipitation over the Tianshan Mountains shows a strong seasonality. In total, 63.6% of all precipitation falls in spring and summer. Distinctive differences are found in seasonal precipitation variations among the sub‐Tianshan regions. Obvious upward trends of precipitation over Eastern Tianshan were found in all seasons, with Eastern Tianshan entering a humid period as early as 1986. Northern and Central Tianshan experienced a decreasing trend in summer and spring. However, in the other seasons, those two sub‐Tianshan regions have been in humid periods since the 1990s. The precipitation over Western Tianshan showed an upward trend in summer and autumn. The obvious downward trends in spring and winter have led to dry periods in these two seasons from 1997–2014 to 2008–2016, respectively.
    Description: Most parts of Tianshan experienced increasing annual precipitation during 1950–2016 while Western Tianshan, which is the wettest region, faced a downtrend of precipitation during the same 67 years. Distinctive differences are found in seasonal precipitation variations among the sub‐Tianshan regions.
    Description: Humboldt‐Universität zu Berlin National Natural Science Foundation of China
    Description: China Scholarship Council (CSC)
    Keywords: ddc:551.6
    Language: English
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    Synoptic circulation changes over Central Europe from 1900 to 2100: Reanalyses and Coupled Model Intercomparison Project phase 6 (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
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    Publication Date: 2022-09-27
    Description: While the evidence for anthropogenic climate change continues to strengthen, and concerns about severe weather events are increasing, global projections of regional climate change are still uncertain due to model‐dependent changes in large‐scale atmospheric circulation, including over North Atlantic and Europe. Here, the Jenkinson–Collison classification of daily circulation patterns is used to evaluate past and future changes in their seasonal frequencies over Central Europe for the 1900–2100 period. Three reanalyses and eight global climate models from the Coupled Model Intercomparison Project phase 6, were used based on daily mean sea‐level pressure data. Best agreement in deriving relative frequencies of the synoptic types was found between the reanalyses. Global models can generally capture the interannual variability of circulation patterns and their climatological state, especially for the less frequent synoptic types. Based on historical data and the shared socioeconomic pathway 5 scenario, the evaluated trends show more robust signals during summer, given their lesser internal variability. Increasing frequencies were found for circulation types characterized by weak pressure gradients, mainly at the expense of decreasing frequencies of westerlies. Our findings indicate that given a high‐emission scenario, these signals will likely emerge from past climate variability towards the mid‐21st century for most altered circulation patterns.
    Description: Daily synoptic circulation patterns are derived using the Jenkinson–Collinson automated classification over Central Europe to evaluate past and future changes in their temporal frequencies. Reanalyses and eight global climate models from the CMIP6 were used based on the historical experiment and a high‐emission scenario. More robust signals were found during the summer season leading to emerging changes towards the mid‐21st century.
    Description: H2020 Marie Skłodowska‐Curie Actions http://dx.doi.org/10.13039/100010665
    Description: EU International Training Network (ITN) Climate Advanced Forecasting of sub‐seasonal Extremes (CAFE)
    Keywords: ddc:551.6
    Language: English
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    Urban pluvial flood adaptation: Results of a household survey across four German municipalities (2021)
    Blackwell Publishing Ltd | Oxford, UK
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    Publication Date: 2022-09-30
    Description: In recent years, German cities were heavily impacted by pluvial flooding and related damage is projected to increase due to climate change and urbanisation. It is important to ask how to improve urban pluvial flood risk management. To understand the current state of property level adaptation, a survey was conducted in four municipalities that had recently been impacted by pluvial flooding. A hybrid framework based on the Protection Motivation Theory (PMT) and the Protection Action Decision Model (PADM) was used to investigate drivers of adaptive behaviour through both descriptive and regression analyses. Descriptive statistics revealed that participants tended to instal more low‐ and medium‐cost measures than high‐cost measures. Regression analyses showed that coping appraisal increased protection motivation, but that the adaptive behaviour also depends on framing factors, particularly homeownership. We further found that, while threat appraisal solely affects protection motivation and responsibility appraisal affects solely maladaptive thinking, coping appraisal affects both. Our results indicate that PMT is a solid starting point to study adaptive behaviours in the context of pluvial flooding, but we need to go beyond that by, for instance, considering factors of the PADM, such as responsibility, ownership, or respondent age, to fully understand this complex decision‐making process.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Keywords: ddc:551.489 ; ddc:363.34
    Language: English
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    Recent evidence for warmer and drier growing seasons in climate sensitive regions of Central America from multiple global datasets (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2022-07-26
    Description: Smallholder livelihoods throughout Central America are built on rain‐fed agriculture and depend on seasonal variations in temperature and precipitation. Recent climatic shifts in this highly diverse region are not well understood due to sparse observations, and as the skill of global climate products have not been thoroughly evaluated. We examine the performance for several reanalysis and satellite‐based global climate data products (CHIRPS/CHIRTS, ERA5, MERRA‐2, PERSIANN‐CDR) as compared to the observation‐based GPCC precipitation dataset. These datasets are then used to evaluate the magnitude and spatial extent of hydroclimatic shifts and changes in aridity and drought over the last four decades. We focus on water‐limited regions that are important for rain‐fed agriculture and particularly vulnerable to further drying, and newly delineate those regions for Central America and Mexico by adapting prior definitions of the Central American Dry Corridor. Our results indicate that the CHIRPS dataset exhibits the greatest skill for the study area. A general warming of 0.2–0.8°C·decade−1 was found across the region, particularly for spring and winter, while widespread drying was indicated by several measures for the summer growing season. Changes in annual precipitation have been inconsistent, but show declines of 20–25% in eastern Honduras/Nicaragua and in several parts of Mexico. Some regions most vulnerable to drying have been subject to statistically significant trends towards summer drying, increases in drought and aridity driven by precipitation declines, and/or a lengthening of the winter dry season, highlighting areas where climate adaptation measures may be most urgent.
    Description: Over the past four decades, precipitation trends are the main driver of drought trends, with temperature trends playing a small role. The most widespread drying and increases in aridity have occurred during the summer growing season. Based on delimitations of water‐limited and climate‐sensitive regions (brown shading) that are important for rain‐fed agriculture, some of these highly vulnerable regions overlap with areas of significant drying (red), highlighting potential prioritization areas for climate adaptation measures. image
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Frias Institute of Advanced Studies (FRIAS) http://dx.doi.org/10.13039/501100003190
    Description: National Science Foundation http://dx.doi.org/10.13039/100000001
    Keywords: ddc:551.6
    Language: English
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