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  • 1
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    Combining Commercial Microwave Link and Rain Gauge Observations to Estimate Countrywide Precipitation: A Stochastic Reconstruction and Pattern Analysis Approach (2022)
    Details
    Publication Date: 2024-02-28
    Description: Accurate spatiotemporal precipitation quantification is a crucial prerequisite for hydrological analyses. The optimal reconstruction of the spatial distribution, that is, the rainfall patterns, is particularly challenging. In this study, we reconstructed spatial rainfall on a countrywide scale for Germany by combining commercial microwave link and rain gauge observations for a better representation of the variability and spatial structure of rainfall. We further developed and applied the Random‐Mixing‐Whittaker‐Shannon method, enabling the stochastic reconstruction of ensembles of spatial fields via linear combinations of unconditional random fields. The pattern of rainfall objects is evaluated by three performance characteristics, that is, ensemble Structure‐, Amplitude‐, and Location‐error. Precipitation estimates obtained are in good agreement with the gauge‐adjusted weather radar product RADOLAN‐RW of the German Weather Service (DWD) which was used as a reference. Compared to reconstructions by Ordinary Kriging, Random Mixing showed clear advantages in the pattern representation via a five times smaller median structure error.
    Description: Plain Language Summary: Rainfall is commonly measured by dedicated sensors such as rain gauges or weather radars. Commercial microwave links (CMLs), which have the primary purpose of signal forwarding within cellular networks, can be used for rainfall measurements too. The signal, which is transmitted from one antenna to another, is being attenuated if it rains along the path. From the amount of attenuation an average rain rate can be retrieved. For many hydrological applications, it is of major interest to estimate area‐wide rainfall (i.e., rainfall maps) while observations provide only scattered information. In this study, we used the local information from almost 1,000 rain gauges and the information along the paths of 3,900 CMLs distributed over Germany to reconstruct rainfall maps. We did this by applying a method of stochastic simulation (called Random Mixing) which we compared to a more common method of estimation (Ordinary Kriging). To evaluate the quality of the obtained maps, we compared them to rainfall information from weather radars. We found that the general agreement is high, and that maps reconstructed by Random Mixing have particular advantages in representing the spatial structure, that is, the shape of rainfall cells.
    Description: Key Points: Geostatistical Random Mixing simulation now capable of countrywide spatial rainfall interpolation. Variability assessment via commercial microwave link path consideration and ensemble estimation. Realistic rainfall pattern representation quantified by ensemble Structure‐, Amplitude‐, and Location‐error metrics.
    Description: German Research Foundation
    Description: Federal Ministry of Education and Research
    Description: https://doi.org/10.5281/zenodo.4810169
    Description: https://opendata.dwd.de/climate_environment/CDC
    Description: https://maps.dwd.de/geoserver/web/wicket/bookmarkable/org.geoserver.web.demo.SRSDescriptionPage?10 26code=EPSG:1000001
    Description: https://doi.org/10.5281/zenodo.5380342
    Description: https://doi.org/10.5281/zenodo.7048941
    Description: https://doi.org/10.5281/zenodo.7049826
    Description: https://doi.org/10.5281/zenodo.7049846
    Keywords: ddc:551.5 ; precipitation estimation ; geostatistical simulation ; spatial pattern analysis ; commercial microwave links ; rain gauges ; random mixing
    Language: English
    Type: doc-type:article
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  • 2
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    High-Resolution Virtual Catchment Simulations of the Subsurface-Land Surface-Atmosphere System (2016)
    Copernicus
    Details
    Publication Date: 2016-11-01
    Description: Combining numerical models, which simulate water and energy fluxes in the subsurface-land surface-atmosphere system in a physically consistent way, becomes increasingly important to understand and study fluxes at compartmental boundaries and interdependencies of states across these boundaries. Complete state evolutions generated by such models, when run at highest possible resolutions while incorporating as many processes as attainable, may be regarded as a proxy of the real world – a virtual reality – which can be used to test hypotheses on functioning of the coupled terrestrial system and may serve as source for virtual measurements to develop data-assimilation methods. Such simulation systems, however, face severe problems caused by the vastly different scales of the processes acting in the compartments of the terrestrial system. The present study is motivated by the development of cross-compartmental data-assimilation methods, which face the difficulty of data scarcity in the subsurface when applied to real data. With appropriate and realistic measurement operators, the virtual reality not only allows taking virtual observations in any part of the terrestrial system at any density, thus overcoming data-scarcity problems of real-world applications, but also provides full information about true states and parameters aimed to be reconstructed from the measurements by data assimilation. In the present study, we have used the Terrestrial Systems Modeling Platform TerrSysMP, which couples the meteorological model COSMO, the land-surface model CLM, and the subsurface model ParFlow, to set up the virtual reality for a regional terrestrial system roughly oriented at the Neckar catchment in southwest Germany. We find that the virtual reality is in many aspects quite close to real observations of the catchment concerning, e.g., atmospheric boundary-layer height, precipitation, and runoff. But also discrepancies become apparent both in the ability of such models to correctly simulate some processes – which still need improvement – and the realism of the results of some observation operators like the SMOS and SMAP sensors, when faced with model states. In a succeeding step, we will use the virtual reality to generate observations in all compartments of the system for coupled data assimilation. The data assimilation will rely on a coarsened and simplified version of the model system.
    Print ISSN: 1812-2108
    Electronic ISSN: 1812-2116
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 3
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    Enriching the isotopic toolbox for migratory connectivity analysis: a new approach for migratory species breeding in remote or unexplored areas (2015)
    Wiley
    Details
    Publication Date: 2015-01-22
    Print ISSN: 1366-9516
    Electronic ISSN: 1472-4642
    Topics: Biology
    Published by Wiley
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  • 4
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    Copula-based downscaling of daily precipitation fields (2018)
    Wiley
    Details
    Publication Date: 2018-09-30
    Description: A novel stochastic downscaling approach to simulate ensembles of daily precipitation fields using the Gaussian copula is presented. In contrast to many other statistical downscaling techniques, this approach uses spatial correlation (correlograms) to derive the transfer function between predictors and predictands for a parsimonious model structure. Daily regional climate model (RCM) simulations for a region in Central Europe in two different spatial resolutions (7 and 42 km) served as a training set to derive the statistics necessary to simulate fine scale precipitation values. The model was calibrated with RCM simulations for the year 1971, and the evaluation was performed for the period 1972–2000 to emulate the typical problem of limited availability of fine scale data. A comprehensive evaluation of the downscaling approach comprising the spatial correlations and statistical distributions of the simulated precipitation fields and several further performance measures was performed. The distribution of simulated precipitation is in close agreement with values simulated from a distribution function that was fitted to the complete evaluation period. Average Brier skill scores of 0.5 indicate a good performance of reproducing the daily dynamical simulations for most regions. A comparison with precipitation fields interpolated with inverse distance weighting revealed an average added skill of 42% for different precipitation thresholds; 87% of the dry days and 71% of the wet days were simulated correctly. An advantage of the proposed method over deterministic downscaling techniques is that ensembles of predictand fields are generated. Thus, the uncertainty that is inherent to downscaling can be estimated. The method has the potential to be used in other downscaling applications to generate ensembles of spatially correlated predictands based on other predictors. As copulas treat the dependence structure separately from the marginal distributions of the predictors and predictands, it is possible to simulate meteorological variables from any desired distribution function. © 2018 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 5
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    Presentation and discussion of the high-resolution atmosphere–land-surface–subsurface simulation dataset of the simulated Neckar catchment for the period 2007–2015 (2021)
    Copernicus
    Details
    Publication Date: 2021-09-14
    Description: Coupled numerical models, which simulate water and energy fluxes in the subsurface–land-surface–atmosphere system in a physically consistent way, are a prerequisite for the analysis and a better understanding of heat and matter exchange fluxes at compartmental boundaries and interdependencies of states across these boundaries. Complete state evolutions generated by such models may be regarded as a proxy of the real world, provided they are run at sufficiently high resolution and incorporate the most important processes. Such a simulated reality can be used to test hypotheses on the functioning of the coupled terrestrial system. Coupled simulation systems, however, face severe problems caused by the vastly different scales of the processes acting in and between the compartments of the terrestrial system, which also hinders comprehensive tests of their realism. We used the Terrestrial Systems Modeling Platform (TerrSysMP), which couples the meteorological Consortium for Small-scale Modeling (COSMO) model, the land-surface Community Land Model (CLM), and the subsurface ParFlow model, to generate a simulated catchment for a regional terrestrial system mimicking the Neckar catchment in southwest Germany, the virtual Neckar catchment. Simulations for this catchment are made for the period 2007–2015 and at a spatial resolution of 400 m for the land surface and subsurface and 1.1 km for the atmosphere. Among a discussion of modeling challenges, the model performance is evaluated based on observations covering several variables of the water cycle. We find that the simulated catchment behaves in many aspects quite close to observations of the real Neckar catchment, e.g., concerning atmospheric boundary-layer height, precipitation, and runoff. But also discrepancies become apparent, both in the ability of the model to correctly simulate some processes which still need improvement, such as overland flow, and in the realism of some observation operators like the satellite-based soil moisture sensors. The whole raw dataset is available for interested users. The dataset described here is available via the CERA database (Schalge et al., 2020): https://doi.org/10.26050/WDCC/Neckar_VCS_v1.
    Print ISSN: 1866-3508
    Electronic ISSN: 1866-3516
    Topics: Geosciences
    Published by Copernicus
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  • 6
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    A Joint Soil‐Vegetation‐Atmospheric Modeling Procedure of Water Isotopologues: Implementation and Application to Different Climate Zones With WRF‐Hydro‐Iso (2021)
    American Geophysical Union
    Details
    Publication Date: 2021-10-01
    Electronic ISSN: 1942-2466
    Topics: Geography , Geosciences
    Published by American Geophysical Union
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  • 7
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    Glacial-interglacial changes of water isotopes (H218O, HDO) 
 as simulated by a fully coupled Earth System Model (2014)
    In:  EPIC3European Geosciences Union General Assembly, Vienna, 2014-04-27-2014-05-02
    Details
    Publication Date: 2014-07-08
    Description: During the past two decades, several atmospheric and oceanic general circulation models (GCMs) have been enhanced by the capability to explicitly simulate the hydrological cycle of the two stable water isotopes H218O and HDO. They have provided a wealth of understanding regarding changes of the water isotope signals in various archives under different past climate conditions. However, so far the number of fully coupled atmosphere-ocean GCMs with explicit water isotope diagnostics is very limited. Such coupled models are required for a more comprehensive simulation of both past climates as well as related isotope changes in the Earth’s hydrological cycle. Here, we report first results of a newly developed isotope diagnostics within the Earth system model ECHAM5-JSBACH/MPIMOM. Both H218O and HDO and their relevant fractionation processes are included in all compartments and branches of the water cycle within this model. First equilibrium simulations have been performed for both pre-industrial (PI) and Last Glacial Maximum (LGM) boundary conditions. Evaluation of the PI simulation reveals a good overall model performance in accordance with available modern isotope data from vapour measurements, precipitation samples as well as marine records. The LGM experiment results in spatially varying isotope depletion in precipitation between -20‰ and 0‰ in agreement with data from various isotope records. The simulated isotopic compoisiton of ccean surface waters shows a strong glacial enrichment in the Arctic. In further model analyses we investigate how the relation between water isotopes and key climate variables, e.g. land and surface temperatures, precipitation amounts, oceanic salinity, might has changed for different regions on a glacial-interglacial time scale. Moreover, the influence of glacial climates changes on second-order isotope signals, e.g. the Deuterium excess, is examined.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 8
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    Stable water isotopes in the coupled atmosphere-land surface model ECHAM5-JSBACH (2013)
    In:  EPIC3Geoscientific Model Development, 6, pp. 1463-1480
    Details
    Publication Date: 2019-07-17
    Description: In this study we present first results of a new model development, ECHAM5-JSBACH-wiso, where we have incorporated the stable water isotopes H218O and HDO as tracers in the hydrological cycle of the coupled atmosphere–land surface model ECHAM5-JSBACH. The ECHAM5-JSBACH-wiso model was run under present-day climate conditions at two different resolutions (T31L19, T63L31). A comparison between ECHAM5-JSBACH-wiso and ECHAM5-wiso shows that the coupling has a strong impact on the simulated temperature and soil wetness. Caused by these changes of temperature and the hydrological cycle, the δ18O in precipitation also shows variations from −4‰ up to 4‰. One of the strongest anomalies is shown over northeast Asia where, due to an increase of temperature, the δ18O in precipitation increases as well. In order to analyze the sensitivity of the fractionation processes over land, we compare a set of simulations with various implementations of these processes over the land surface. The simulations allow us to distinguish between no fractionation, fractionation included in the evaporation flux (from bare soil) and also fractionation included in both evaporation and transpiration (from water transport through plants) fluxes. While the isotopic composition of the soil water may change for δ18O by up to +8‰:, the simulated δ18O in precipitation shows only slight differences on the order of ±1‰. The simulated isotopic composition of precipitation fits well with the available observations from the GNIP (Global Network of Isotopes in Precipitation) database.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Glacial-interglacial changes 
of water isotopes (H218O, HDO) 
 as simulated by a 
fully coupled Earth System Model (2014)
    In:  EPIC3AGU Fall Meeting, San Francisco, 2014-12-15-2014-12-19
    Details
    Publication Date: 2015-02-03
    Description: During the past two decades, several atmospheric and oceanic general circulation models (GCMs) have been enhanced by the capability to explicitly simulate the hydrological cycle of the two stable water isotopes H218O and HDO. They have provided a wealth of understanding regarding changes of the water isotope signals in various archives under different past climate conditions. However, so far the number of fully coupled atmosphere-ocean GCMs with explicit water isotope diagnostics is very limited. Such coupled models are required for a more comprehensive simulation of both past climates as well as related isotope changes in the Earth’s hydrological cycle. Here, we report first results of a newly developed isotope diagnostics within the Earth system model ECHAM5-JSBACH/MPIMOM. Both H218O and HDO and their relevant fractionation processes are included in all compartments and branches of the water cycle within this model. First equilibrium simulations have been performed for both pre-industrial (PI) and Last Glacial Maximum (LGM) boundary conditions. Evaluation of the PI simulation reveals a good overall model performance in accordance with available modern isotope data from vapor measurements, precipitation samples as well as marine records. For precipitation, root-mean-square error (RMSE) between model results and GNIP δ18O data is approx. 3‰. For ocean surface water, model results and GISS δ18O observational data deviate by 1‰ RMSE or less, with strongest differences in the Arctic Ocean. The LGM experiment results in spatially varying isotope depletion in precipitation between -20‰ and 0‰ in agreement with data from various isotope records. The isotope data clearly mirrors a temperature change of similar range. For the ocean surface waters, the simulated isotopic composition shows a strong glacial enrichment in the North Atlantic of more than +0.5‰. In combination with glacial SST changes a LGM calcite δ18O enrichment of +2.5‰ is simulated. Analyses of the simulated Deuterium excess changes with Antarctic ice core data reveal a good model-data agreement and support the hypothesis of rather cool tropical SST during the last glacial maximum.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 10
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    Modelling water isotopes for an improved interpretation of climate proxy records (2012)
    In:  EPIC33rd International Conference on Earth System Modelling (3ICESM), Hamburg, Germany, 2012-09-17-2012-09-21
    Details
    Publication Date: 2019-07-17
    Description: During the past two decades, several atmospheric and oceanic general circulation models (GCMs) have been enhanced by the capability to explicitly simulate the hydrological cycle of the two stable water isotopes H218O and HDO. A number of previous studies have demonstrated the possibility of an improved interpretation of observed isotope variability in terms of climate change by such isotope GCM simulations. Here, we report new results of the ECHAM5 atmosphere GCM enhanced by explicit water isotope diagnosis (named ECHAM5-wiso hereafter). Several simulations covering climate changes in the range of the last decades up to glacial-interglacial cycles have been performed to evaluate the overall capability of the ECHAM5-wiso model and to enable a more quantitative interpretation of various isotope paleoarchives. All simulations have been performed with a high spatial model resolution of approx. 1° (T106 spectral mode) or finer. It is shown that the refinement of the spatial resolution leads to a substantially better agreement with available present-day observations and isotopic paleorecords, e.g. Antarctic ice core data. Using this new set of paleoclimate simulations, we investigate if and how climate variability is imprinted in the isotopic composition of precipitation on different time scales. Special focus is given to the question how the temperature-isotope relation might has changed in different regions of the Earth on the various time scale. The atmospheric isotope GCM results are complemented by first oceanic isotope GCM simulation results with the MPI-OM model as well as investigations of the influence of paleovegetation changes on the hydrological cycle and its isotopic composition, as simulated by an isotope-enhanced ECHAM5/JSBACH model setup.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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