ALBERT

Description: Magnetotelluric investigation in the High Agri Valley (southern Apennine, Italy) Natural Hazards and Earth System Sciences Discussions, 2, 6747-6773, 2014 Author(s): M. Balasco, A. Giocoli, S. Piscitelli, G. Romano, A. Siniscalchi, T. A. Stabile, and S. Tripladi In this paper we present the result of a Magnetotelluric (MT) investigation carried out across the High Agri Valley (HAV), southern Italy. Several MT soundings were carried out in order to obtain a ~15 km long 2-D resistivity model with an investigation depth of ~10 km. The main aim was to provide valuable data on the geological and structural setting of the HAV. The MT model was compared with pre-existing geological, geophysical and seismic data. The MT model can be schematized as a superposition of three stack lateral varying layers with different thickness and resistivity values: a surficial low-medium resistivity layer, associated to the Quaternary deposits and to the allochthonous units, and a deeper high resistivity layer, related to the Apulia Platform, separated by a thin layer connected to the mélange zone and to the Pliocene terrigenous marine deposits. Sharp lateral resistivity variations are interpreted as faults that, on the basis of accurate focal mechanism computations, display normal-faulting kinematics.

Description: Temperature distribution and Hadley circulation in an axisymmetric model Nonlinear Processes in Geophysics Discussions, 1, 1621-1655, 2014 Author(s): N. Tartaglione The impact of the temperature distribution on the Hadley circulation simulated by an axisymmetric model is studied. The temperature distributions that drive the model are modulated here by two parameters, n and k , the former controlling the horizontal broadness and the latter defining change in the vertical lapse rate. In the present study, the changes of the temperature distribution mimic changes of the energy input of the atmospheric system leaving as an invariant the equator-poles difference. Both equinoctial and time-dependent Hadley circulations are simulated and results compared. The results give evidence that concentrated temperature distributions enhance the meridional circulation and jet wind speed intensities even with a lower energy input. The meridional circulation and the subtropical jet stream widths are controlled by the broadness of horizontal temperature rather than the vertical lapse rate k , which is important only when the temperature distribution is concentrated at the equator. The jet stream position does not show any dependence with n and k , except when the temperature distribution is very wide and in such a case the jet is located at the mid-latitude. Using n = 2 and k = 1 we have the formulation of the potential temperature adopted in classical literature. A comparison with other works is performed and our results show that the model running in different configurations (equinoctial, solstitial and time-dependent) yields results similar to one another.

Description: Regional parent flood frequency distributions in Europe – Part 2: Climate and scale controls Hydrology and Earth System Sciences, 18, 4391-4401, 2014 Author(s): J. L. Salinas, A. Castellarin, S. Kohnová, and T. R. Kjeldsen This study aims to better understand the effect of catchment scale and climate on the statistical properties of regional flood frequency distributions. A database of L-moment ratios of annual maximum series (AMS) of peak discharges from Austria, Italy and Slovakia, involving a total of 813 catchments with more than 25 yr of record length is presented, together with mean annual precipitation (MAP) and basin area as catchment descriptors surrogates of climate and scale controls. A purely data-based investigation performed on the database shows that the generalized extreme value (GEV) distribution provides a better representation of the averaged sample L-moment ratios compared to the other distributions considered, for catchments with medium to higher values of MAP independently of catchment area, while the three-parameter lognormal distribution is probably a more appropriate choice for drier (lower MAP) intermediate-sized catchments, which presented higher skewness values. Sample L-moment ratios do not follow systematically any of the theoretical two-parameter distributions. In particular, the averaged values of L-coefficient of skewness (L-Cs) are always larger than Gumbel 's fixed L-Cs. The results presented in this paper contribute to the progress in defining a set of "process-driven" pan-European flood frequency distributions and to assess possible effects of environmental change on its properties.

Description: Wind waves in the Black Sea: results of a hindcast study Natural Hazards and Earth System Science, 14, 2883-2897, 2014 Author(s): V. S. Arkhipkin, F. N. Gippius, K. P. Koltermann, and G. V. Surkova In this study we describe the wind wave fields in the Black Sea. The general aims of the work were the estimation of statistical wave parameters and the assessment of interannual and seasonal wave parameter variability. The domain of this study was the entire Black Sea. Wave parameters were calculated by means of the SWAN wave model on a 5 × 5 km rectangular grid. Initial conditions (wind speed and direction) for the period between 1949 and 2010 were derived from the NCEP/NCAR reanalysis. According to our calculations the average significant wave height on the Black Sea does not exceed 0.7 m. Areas of most significant heavy sea are the southwestern and the northeastern parts of the sea as expressed in the spatial distribution of significant wave heights, wave lengths and periods. Besides, long-term annual variations of wave parameters were estimated. Thus, linear trends of the annual total duration of storms and of their quantity are nearly stable over the hindcast period. However, an intensification of storm activity is observed in the 1960s–1970s.

Description: Dynamics of turbulent western boundary currents at low latitude in a shallow water model Ocean Science Discussions, 11, 2461-2493, 2014 Author(s): C. Q. C. Akuetevi and A. Wirth The dynamics of low latitude turbulent western boundary currents crossing the equator is considered using numerical results from integrations of a reduced gravity shallow-water model. For viscosity values of 1000 m 2 s −1 and more, the boundary layer dynamics compares well to the analytical Munk-layer solution. When the viscosity is reduced, the boundary layer becomes turbulent and coherent structures in form of anticyclonic eddies, bursts (violent detachments of the viscous sub-layer) and dipoles appear. Three distinct boundary layers emerge, the viscous sub-layer, the advective boundary layer and the extended boundary layer. The first is characterized by a dominant vorticity balance between the viscous transport and the advective transport of vorticity. The second by a balance between the advection of planetary vorticity and the advective transport of relative vorticity. The extended boundary layer is the area to which turbulent motion from the boundary extends. The scaling of the three boundary layer thicknesses with viscosity is evaluated. Characteristic scales of the dynamics and dissipation are determined. A pragmatic approach to determine the eddy viscosity diagnostically for coarse resolution numerical models is proposed.

Description: Estimation of three-dimensional crustal movements in the 2011 Tohoku-oki, Japan earthquake from TerraSAR-X intensity images Natural Hazards and Earth System Sciences Discussions, 2, 7383-7408, 2014 Author(s): W. Liu, F. Yamazaki, M. Matsuoka, T. Nonaka, and T. Sasagawa The Tohoku-Oki earthquake on 11 March 2011 caused significant widespread crustal movements. In a previous study, we proposed a method for capturing two-dimensional (2-D) surface displacements from a pair of pre- and post-event TerraSAR-X (TSX) intensity images. However, it is difficult to detect three-dimensional (3-D) displacements from one pair of TSX images. In this study, three pairs of pre- and post-event TSX images taken on different paths were used to estimate 3-D crustal movements. The relationship between the actual 3-D displacements and the converted 2-D movements in the SAR images was derived based on the observation model of a SAR sensor. The 3-D movements were then calculated from three sets of detected 2-D movements that occurred within a short time period. Compared with GPS observations, the proposed method was found to be capable of detecting the 3-D crustal movements with sub-pixel accuracy.

Description: Potential of the TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor for the monitoring of terrestrial chlorophyll fluorescence Atmospheric Measurement Techniques Discussions, 7, 12545-12588, 2014 Author(s): L. Guanter, I. Aben, P. Tol, J. M. Krijger, A. Hollstein, P. Köhler, A. Damm, J. Joiner, C. Frankenberg, and J. Landgraf Global monitoring of sun-induced chlorophyll fluorescence (SIF) can improve our knowledge about the photosynthetic functioning of terrestrial ecosystems. The feasibility of SIF retrievals from spaceborne atmospheric spectrometers has been demonstrated by a number of studies in the last years. In this work, we investigate the potential of the upcoming TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor satellite mission for SIF retrieval. TROPOMI will sample the 675–775 nm spectral window with a spectral resolution of 0.5 nm and a pixel size of 7 km × 7 km. We use an extensive set of simulated TROPOMI data in order to assess the uncertainty of single SIF retrievals and subsequent spatio-temporal composites. Our results illustrate the enormous improvement in SIF monitoring achievable with TROPOMI with respect to comparable spectrometers currently in-flight, such as the Global Ozone Monitoring Experiment-2 (GOME-2) instrument. We find that TROPOMI can reduce global uncertainties in SIF mapping by more than a factor 2 with respect to GOME-2, which comes together with an about 5-fold improvement in spatial sampling. Finally, we discuss the potential of TROPOMI to accurately map other important vegetation parameters, such as leaf photosynthetic pigments and proxies for canopy structure, which will complement SIF retrievals for a self-contained description of vegetation condition and functioning.

Description: Emission of iodine-containing volatiles by selected microalgae species Atmospheric Chemistry and Physics, 14, 13327-13335, 2014 Author(s): U. R. Thorenz, L. J. Carpenter, R.-J. Huang, M. Kundel, J. Bosle, and T. Hoffmann In this study we present the results of an emission study of different phytoplankton samples in aqueous media treated with elevated ozone levels. Halocarbon measurements show that the samples tested released bromoform and different iodocarbons, including iodomethane, iodochloromethane and diiodomethane. Iodide and iodate levels in the liquid phase were representative of concentrations of surface water in a natural environment. Measurement of volatile iodine (I 2 ) emissions from two diatom samples ( Mediopyxis helysia and Porosira glacialis ) and the background sample (F/2 medium from filtered natural seawater) showed that the quantity of evolved I 2 depends on the ozone concentration in the air. This behaviour was assumed to be caused by the oxidation reaction mechanism of iodide with ozone. The I 2 emission flux agrees with model calculations at different iodide concentrations. The I 2 emission of a natural plankton concentrate sample was, however, very low compared to other samples and showed no dependence on ozone. The reason for this was shown to be the low iodide concentration in the algal suspension, which seems to be the limiting factor in the oxidative formation of I 2 .

Description: A global model simulation for 3-D radiative transfer impact on surface hydrology over Sierra Nevada and Rocky Mountains Atmospheric Chemistry and Physics Discussions, 14, 31603-31625, 2014 Author(s): W.-L. Lee, Y. Gu, K. N. Liou, L. R. Leung, and H.-H. Hsu We investigate 3-D mountain effects on solar flux distributions and their impact on surface hydrology over the Western United States, specifically the Rocky Mountains and Sierra Nevada using CCSM4 (CAM4/CLM4) global model with a 0.23° × 0.31° resolution for simulations over 6 years. In 3-D radiative transfer parameterization, we have updated surface topography data from a resolution of 1 km to 90 m to improve parameterization accuracy. In addition, we have also modified the upward-flux deviation [3-D − PP (plane-parallel)] adjustment to ensure that energy balance at the surface is conserved in global climate simulations based on 3-D radiation parameterization. We show that deviations of the net surface fluxes are not only affected by 3-D mountains, but also influenced by feedbacks of cloud and snow in association with the long-term simulations. Deviations in sensible heat and surface temperature generally follow the patterns of net surface solar flux. The monthly snow water equivalent (SWE) deviations show an increase in lower elevations due to reduced snowmelt, leading to a reduction in cumulative runoff. Over higher elevation areas, negative SWE deviations are found because of increased solar radiation available at the surface. Simulated precipitation increases for lower elevations, while decreases for higher elevations with a minimum in April. Liquid runoff significantly decreases in higher elevations after April due to reduced SWE and precipitation.

Description: Autonomous profiling float observations of the high biomass plume downstream of the Kerguelen plateau in the Southern Ocean Biogeosciences Discussions, 11, 17413-17462, 2014 Author(s): M. Grenier, A. Della Penna, and T. W. Trull Natural iron fertilisation from Southern Ocean islands results in high primary production and phytoplankton biomass accumulations readily visible in satellite ocean colour observations. These images reveal great spatial complexity with highly varying concentrations of chlorophyll, presumably reflecting both variations in iron supply and conditions favouring phytoplankton accumulation. To examine the second aspect, in particular the influences of variations in temperature and stratification, we deployed four autonomous profiling floats in the Antarctic Circumpolar Current near the Kerguelen plateau in the Indian sector of the Southern Ocean. Each "bio-profiler" measured more than 250 profiles of temperature ( T ), salinity ( S ), dissolved oxygen, chlorophyll fluorescence (Chl a ), and particle backscatter in the top 300 m of the water column, sampling up to 5 profiles per day along meandering trajectories extending up to 1000 km. Comparison of surface Chl a estimates (top 50 m depth; analogous to values from satellite images) with total water column inventories revealed largely linear relationships, suggesting that dilution of chlorophyll by mixed layer depth variations plays only a minor role in the spatial distributions observed by satellite, and correspondingly that these images provide credible information on total and not just surface biomass accumulations. Regions of very high Chl a accumulation (1.5–10 μg L -1 ) were associated predominantly with a narrow T – S class of surface waters, which appears to derive from the northern Kerguelen plateau. In contrast, waters with only moderate Chl a enrichments (0.5–1.5 μg L -1 ) displayed no clear correlation with water properties, including no dependence on mixed layer depth, suggesting a diversity of sources of iron and/or its efficient dispersion across filaments of the plume. The lack of dependence on mixed layer depth also indicates a limited influence on production by light limitation. One float became trapped in a cyclonic eddy, allowing temporal evaluation of the water column in early autumn. During this period, decreasing surface Chl a inventories corresponded with decreases in oxygen inventories on sub-mixed layer density surfaces, consistent with significant export of organic matter and its respiration and storage as dissolved inorganic carbon in the ocean interior. These results are encouraging for the expanded use of autonomous observing platforms to study biogeochemical, carbon cycle, and ecological problems, although the complex blend of Lagrangian and Eulerian sampling achieved by the floats suggests that arrays rather than single floats will often be required.

Description: Tectonic and climatic controls on the Chuquibamba landslide (western Andes, southern Peru) Earth Surface Dynamics Discussions, 2, 1129-1153, 2014 Author(s): A. Margirier, L. Audin, J. Carcaillet, and S. Schwartz The contribution of landslides to the Quaternary evolution of reliefs is poorly documented in arid contexts. In southern Peru and northern Chile several massive landslides disrupt the arid western Andean front. The Chuquibamba landslide, located in southern Peru, belongs to this set of large landslides. In this area, the Incapuquio fault system captures the intermittent drainage network and localizes rotational landslides. Seismic activity is significant in this region with recurrent M w = 9 subduction earthquakes, however none of the latest seismic events have triggered a major landslide. New terrestrial cosmogenic dating of the Chuquibamba landslide provides evidence that the last major gravitational mobilization of these rotational landslide deposits occurred at ~102 ka, during the Ouki wet climatic event identified on the Altiplano between 120 and 98 ka. Our results suggest that wet events in the arid and fractured context of the Andean forearc induced these giant debris-flows. Finally, our study highlights the role of tectonics and climate on (i) the localization of large Andean landslides and on (ii) the long-term mass transfer to the trench along the arid Andean front.

Description: Quantification of hydrologic impacts of climate change in a Mediterranean basin in Sardinia, Italy, through high-resolution simulations Hydrology and Earth System Sciences, 18, 5201-5217, 2014 Author(s): M. Piras, G. Mascaro, R. Deidda, and E. R. Vivoni Future climate projections robustly indicate that the Mediterranean region will experience a significant decrease of mean annual precipitation and an increase in temperature. These changes are expected to seriously affect the hydrologic regime, with a limitation of water availability and an intensification of hydrologic extremes, and to negatively impact local economies. In this study, we quantify the hydrologic impacts of climate change in the Rio Mannu basin (RMB), an agricultural watershed of 472.5 km 2 in Sardinia, Italy. To simulate the wide range of runoff generation mechanisms typical of Mediterranean basins, we adopted a physically based, distributed hydrologic model. The high-resolution forcings in reference and future conditions (30-year records for each period) were provided by four combinations of global and regional climate models, bias-corrected and downscaled in space and time (from ~25 km, 24 h to 5 km, 1 h) through statistical tools. The analysis of the hydrologic model outputs indicates that the RMB is expected to be severely impacted by future climate change. The range of simulations consistently predict (i) a significant diminution of mean annual runoff at the basin outlet, mainly due to a decreasing contribution of the runoff generation mechanisms depending on water available in the soil; (ii) modest variations in mean annual runoff and intensification of mean annual discharge maxima in flatter sub-basins with clay and loamy soils, likely due to a higher occurrence of infiltration excess runoff; (iii) reduction of soil water content and actual evapotranspiration in most areas of the basin; and (iv) a drop in the groundwater table. Results of this study are useful to support the adoption of adaptive strategies for management and planning of agricultural activities and water resources in the region.

Description: Complex networks, streamflow, and hydrometric monitoring system design Hydrology and Earth System Sciences Discussions, 11, 13663-13710, 2014 Author(s): M. Halverson and S. Fleming Network theory is applied to an array of streamflow gauges located in the Coast Mountains of British Columbia and Yukon, Canada. The goal of the analysis is to assess whether insights from this branch of mathematical graph theory can be meaningfully applied to hydrometric data, and more specifically, whether it may help guide decisions concerning stream gauge placement so that the full complexity of the regional hydrology is efficiently captured. The streamflow data, when represented as a complex network, has a global clustering coefficient and average shortest path length consistent with small-world networks, which are a class of stable and efficient networks common in nature, but the results did not clearly suggest a scale-free network. Stability helps ensure that the network is robust to the loss of nodes; in the context of a streamflow network, stability is interpreted as insensitivity to station removal at random. Community structure is also evident in the streamflow network. A community detection algorithm identified 10 separate communities, each of which appears to be defined by the combination of its median seasonal flow regime (pluvial, nival, hybrid, or glacial, which in this region in turn mainly reflects basin elevation) and geographic proximity to other communities (reflecting shared or different daily meteorological forcing). Betweenness analyses additionally suggest a handful of key stations which serve as bridges between communities and might therefore be highly valued. We propose that an idealized sampling network should sample high-betweenness stations, as well as small-membership communities which are by definition rare or undersampled relative to other communities, while retaining some degree of redundancy to maintain network robustness.

Description: A strategy for GIS-based 3-D slope stability modelling over large areas Geoscientific Model Development, 7, 2969-2982, 2014 Author(s): M. Mergili, I. Marchesini, M. Alvioli, M. Metz, B. Schneider-Muntau, M. Rossi, and F. Guzzetti GIS-based deterministic models may be used for landslide susceptibility mapping over large areas. However, such efforts require specific strategies to (i) keep computing time at an acceptable level, and (ii) parameterize the geotechnical data. We test and optimize the performance of the GIS-based, 3-D slope stability model r.slope.stability in terms of computing time and model results. The model was developed as a C- and Python-based raster module of the open source software GRASS GIS and considers the 3-D geometry of the sliding surface. It calculates the factor of safety (FoS) and the probability of slope failure ( P f ) for a number of randomly selected potential slip surfaces, ellipsoidal or truncated in shape. Model input consists of a digital elevation model (DEM), ranges of geotechnical parameter values derived from laboratory tests, and a range of possible soil depths estimated in the field. Probability density functions are exploited to assign P f to each ellipsoid. The model calculates for each pixel multiple values of FoS and P f corresponding to different sliding surfaces. The minimum value of FoS and the maximum value of P f for each pixel give an estimate of the landslide susceptibility in the study area. Optionally, r.slope.stability is able to split the study area into a defined number of tiles, allowing parallel processing of the model on the given area. Focusing on shallow landslides, we show how multi-core processing makes it possible to reduce computing times by a factor larger than 20 in the study area. We further demonstrate how the number of random slip surfaces and the sampling of parameters influence the average value of P f and the capacity of r.slope.stability to predict the observed patterns of shallow landslides in the 89.5 km 2 Collazzone area in Umbria, central Italy.

Description: Northern Hemisphere storminess in the Norwegian Earth System Model (NorESM1-M) Geoscientific Model Development Discussions, 7, 8975-9015, 2014 Author(s): E. M. Knudsen and J. E. Walsh Metrics of storm activity in Northern Hemisphere high- and midlatitudes are evaluated from historical output and future projections by the Norwegian Earth System Model (NorESM1-M) coupled global climate model. The European Re-Analysis Interim (ERA-Interim) and the Community Climate System Model (CCSM4), a global climate model of the same vintage as NorESM1-M, provide benchmarks for comparison. The focus is on the autumn and early winter (September through December), the period when the ongoing and projected Arctic sea ice retreat is greatest. Storm tracks derived from a vorticity-based algorithm for storm identification are reproduced well by NorESM1-M, although the tracks are somewhat better resolved in the higher-resolution ERA-Interim and CCSM4. The tracks are projected to shift polewards in the future as climate changes under the Representative Concentration Pathway (RCP) forcing scenarios. Cyclones are projected to become generally more intense in the high-latitudes, especially over the Alaskan region, although in some other areas the intensity is projected to decrease. While projected changes in track density are less coherent, there is a general tendency towards less frequent storms in midlatitudes and more frequent storms in high-latitudes, especially the Baffin Bay/Davis Strait region. Autumn precipitation is projected to increase significantly across the entire high-latitudes. Together with the projected increases in storm intensity and sea level and the loss of sea ice, this increase in precipitation implies a greater vulnerability to coastal flooding and erosion, especially in the Alaskan region. The projected changes in storm intensity and precipitation (as well as sea ice and sea level pressure) scale generally linearly with the RCP value of the forcing and with time through the 21st century.

Description: Assessing winter cover crop nutrient uptake efficiency using a water quality simulation model Hydrology and Earth System Sciences, 18, 5239-5253, 2014 Author(s): I.-Y. Yeo, S. Lee, A. M. Sadeghi, P. C. Beeson, W. D. Hively, G. W. McCarty, and M. W. Lang Winter cover crops are an effective conservation management practice with potential to improve water quality. Throughout the Chesapeake Bay watershed (CBW), which is located in the mid-Atlantic US, winter cover crop use has been emphasized, and federal and state cost-share programs are available to farmers to subsidize the cost of cover crop establishment. The objective of this study was to assess the long-term effect of planting winter cover crops to improve water quality at the watershed scale (~ 50 km 2 ) and to identify critical source areas of high nitrate export. A physically based watershed simulation model, Soil and Water Assessment Tool (SWAT), was calibrated and validated using water quality monitoring data to simulate hydrological processes and agricultural nutrient cycling over the period of 1990–2000. To accurately simulate winter cover crop biomass in relation to growing conditions, a new approach was developed to further calibrate plant growth parameters that control the leaf area development curve using multitemporal satellite-based measurements of species-specific winter cover crop performance. Multiple SWAT scenarios were developed to obtain baseline information on nitrate loading without winter cover crops and to investigate how nitrate loading could change under different winter cover crop planting scenarios, including different species, planting dates, and implementation areas. The simulation results indicate that winter cover crops have a negligible impact on the water budget but significantly reduce nitrate leaching to groundwater and delivery to the waterways. Without winter cover crops, annual nitrate loading from agricultural lands was approximately 14 kg ha −1 , but decreased to 4.6–10.1 kg ha −1 with cover crops resulting in a reduction rate of 27–67% at the watershed scale. Rye was the most effective species, with a potential to reduce nitrate leaching by up to 93% with early planting at the field scale. Early planting of cover crops (~ 30 days of additional growing days) was crucial, as it lowered nitrate export by an additional ~ 2 kg ha −1 when compared to late planting scenarios. The effectiveness of cover cropping increased with increasing extent of cover crop implementation. Agricultural fields with well-drained soils and those that were more frequently used to grow corn had a higher potential for nitrate leaching and export to the waterways. This study supports the effective implementation of cover crop programs, in part by helping to target critical pollution source areas for cover crop implementation.

Description: Preface: Environmental benefits of biochar Solid Earth, 5, 1301-1303, 2014 Author(s): J. Paz-Ferreiro, A. Méndez, A. M. Tarquis, A. Cerdà, and G. Gascó

Description: Amalgamation in landslide maps: effects and automatic detection Natural Hazards and Earth System Sciences Discussions, 2, 7651-7678, 2014 Author(s): O. Marc and N. Hovius Inventories of individually delineated landslides are a key to understanding landslide physics and mitigating their impact. They permit assessment of area-frequency distributions and landslide volumes, and testing of statistical correlations between landslides and physical parameters such as topographic gradient or seismic strong motion. Amalgamation, i.e. the mapping of several adjacent landslides as a single polygon, can lead to potentially severe distortion of the statistics of these inventories. This problem can be especially severe in datasets produced by automated mapping. We present 5 inventories of earthquake-induced landslides mapped with different materials and techniques and affected by varying degrees of amalgamation. Errors on the total landslide volume and power-law exponent of the area-frequency distribution, resulting from amalgamation, may be up to 200 and 50%, respectively. We present an algorithm based on image and DEM analysis, for automatic identification of amalgamated polygons. On a set of about 2000 polygons larger than 1000 m 2 , tracing landslides triggered by the 1994 Northridge earthquake, the algorithm performs well, with only 2.7–3.6% wrongly amalgamated landslides missed and 3.9–4.8% correct polygons wrongly identified as amalgams. This algorithm can be used broadly to check landslide inventories and allow faster correction by automating the identification of amalgamation.

Description: Long-term variability of dust events in Iceland (1949–2011) Atmospheric Chemistry and Physics, 14, 13411-13422, 2014 Author(s): P. Dagsson-Waldhauserova, O. Arnalds, and H. Olafsson The long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and interpreted together with earlier results obtained from northeastern (NE) Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust observations. However, frequent volcanic eruptions, with the re-suspension of volcanic materials and dust haze, increased the number of dust events fourfold (135 dust days annually). The position of the Icelandic Low determined whether dust events occurred in the NE (16.4 dust days annually) or in the southern (S) part of Iceland (about 18 dust days annually). The decade with the most frequent dust days in S Iceland was the 1960s, but the 2000s in NE Iceland. A total of 32 severe dust storms (visibility 〈 500 m) were observed in Iceland with the highest frequency of events during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm, occurring during summer/autumn (May–September) and during mild southwesterly winds, while the subarctic dust events (S Iceland) were mainly cold, occurring during winter/spring (March–May) and during strong northeasterly winds. About half of the dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between particulate matter (PM 10 ) concentrations and visibility during dust observations at the stations Vík and Stórhöfði. This study shows that Iceland is among the dustiest areas of the world and that dust is emitted year-round.

Description: On the origin of the occasional spring nitrate peak in Greenland snow Atmospheric Chemistry and Physics, 14, 13361-13376, 2014 Author(s): L. Geng, J. Cole-Dai, B. Alexander, J. Erbland, J. Savarino, A. J. Schauer, E. J. Steig, P. Lin, Q. Fu, and M. C. Zatko Ice core nitrate concentrations peak in the summer in both Greenland and Antarctica. Two nitrate concentration peaks in one annual layer have been observed some years in ice cores in Greenland from samples dating post-1900, with the additional nitrate peak occurring in the spring. The origin of the spring nitrate peak was hypothesized to be pollution transport from the mid-latitudes in the industrial era. We performed a case study on the origin of a spring nitrate peak in 2005 measured from a snowpit at Summit, Greenland, covering 3 years of snow accumulation. The effect of long-range transport of nitrate on this spring peak was excluded by using sulfate as a pollution tracer. The isotopic composition of nitrate (δ 15 N, δ 18 O and Δ 17 O) combined with photochemical calculations suggest that the occurrence of this spring peak is linked to a significantly weakened stratospheric ozone (O 3 ) layer. The weakened O 3 layer resulted in elevated UVB (ultraviolet-B) radiation on the snow surface, where the production of OH and NO x from the photolysis of their precursors was enhanced. Elevated NO x and OH concentrations resulted in enhanced nitrate production mainly through the NO 2 + OH formation pathway, as indicated by decreases in δ 18 O and Δ 17 O of nitrate associated with the spring peak. We further examined the nitrate concentration record from a shallow ice core covering the period from 1772 to 2006 and found 19 years with double nitrate peaks after the 1950s. Out of these 19 years, 14 of the secondary nitrate peaks were accompanied by sulfate peaks, suggesting long-range transport of nitrate as their source. In the other 5 years, low springtime O 3 column density was observed, suggesting enhanced local production of nitrate as their source. The results suggest that, in addition to direct transport of nitrate from polluted regions, enhanced local photochemistry can also lead to a spring nitrate peak. The enhanced local photochemistry is probably associated with the interannual variability of O 3 column density in the Arctic, which leads to elevated surface UV radiation in some years. In this scenario, enhanced photochemistry caused increased local nitrate production under the condition of elevated local NO x abundance in the industrial era.

Description: Spatial and temporal variation of CO over Alberta using measurements from satellite, aircrafts, and ground stations Atmospheric Chemistry and Physics Discussions, 14, 31767-31812, 2014 Author(s): H. S. Marey, Z. Hashisho, L. Fu, and J. Gille Alberta is Canada's largest oil producer and its oil sand deposits comprise 30% of the world's oil reserves. The process of bitumen extraction and upgrading releases trace gases and aerosols to the atmosphere. In this study we present satellite-based analysis to explore, for the first time, various contributing factors that affect tropospheric carbon monoxide (CO) levels over Alberta. The multispectral product that uses both near-infrared (NIR) and the thermal-infrared (TIR) radiances for CO retrieval from the Measurements of Pollution in the Troposphere (MOPITT) are examined for the 12 year period from 2002–2013. Moderate Resolution Imaging Spectroradiometer (MODIS) thermal anomaly product from 2001 to 2013 is employed to investigate the seasonal and temporal variations of forest fires. Additionally, in situ CO measurements at industrial and urban sites are compared to satellite data. Furthermore, the available MOZAIC/IAGOS (Measurement of Ozone, Water Vapor, Carbon Monoxide, Nitrogen Oxide by Airbus In-Service Aircraft/In service Aircraft for Global Observing System) aircraft CO profiles (April 2009–December 2011) are used to validate MOPITT CO data. The climatological time curtain plot and spatial maps for CO over northern Alberta indicate the signatures of transported CO for two distinct biomass burning seasons, summer and spring. Distinct seasonal patterns of CO at the urban site s (Edmonton and Calgary cities) point to the strong influence of traffic. Meteorological parameters play an important role on the CO spatial distribution at various pressure levels. Northern Alberta shows stronger upward lifting motion which leads to larger CO total column values while the poor dispersion in central and south Alberta exacerbate s the surface CO pollution. Inter-annual variations of satellite data depict a slightly decreasing trend for both regions while the decline trend is more evident from ground observations, especially at the urban sites. MOPITT CO vertical averages and MOZAIC/IAGOS aircraft profiles were in good agreement within the standard deviation at all pressure levels. There is consistency between the time evolution of high CO episodes monitored by satellite and ground measurements and the fire frequency peak time which implies that biomass burning has affected the tropospheric CO distribution in northern Alberta. These findings have further demonstrated the potential use of MOPITT V5 multispectral (NIR+TIR) product for assessing a complicated surface process.

Description: Particulate emissions from residential wood combustion in Europe – revised estimates and an evaluation Atmospheric Chemistry and Physics Discussions, 14, 31719-31765, 2014 Author(s): H. A. C. Denier van der Gon, R. Bergström, C. Fountoukis, C. Johansson, S. N. Pandis, D. Simpson, and A. Visschedijk Currently residential wood combustion (RWC) is increasing in Europe because of rising fossil fuel prices but also due to climate change mitigation policies. However, especially in small-scale applications, RWC may cause high emissions of particulate matter (PM). Recently we have developed a new high-resolution (7 km × 7 km) anthropogenic carbonaceous aerosol emission inventory for Europe. The inventory indicated that about half of the total PM 2.5 emission in Europe is carbonaceous aerosol and identified RWC as the largest organic aerosol (OA) source in Europe. The inventory was partly based on national reported PM emissions. Use of this OA inventory as input for two Chemical Transport Models (CTMs), PMCAMx and EMEP MSC-W, revealed major underestimations of OA in winter time, especially for regions dominated by RWC. Interestingly, this was not universal but appeared to differ by country. In the present study we constructed a new bottom-up emission inventory for RWC accounting for the semi-volatile components of the emissions. The new RWC emissions are higher than those in the previous inventory by a factor of 2–3 but with substantial inter-country variation. The new emission inventory served as input for the CTMs and a substantially improved agreement between measured and predicted organic aerosol was found. The new RWC inventory improves the model calculated OA significantly. Comparisons to Scandinavian source apportionment studies also indicate substantial improvements in the modeled wood-burning component of OA. This suggests that primary organic aerosol emission inventories need to be revised to include the semi-volatile OA that is formed almost instantaneously due to cooling of the flue gas or exhaust. Since RWC is a key source of fine PM in Europe, a major revision of the emission estimates as proposed here is likely to influence source-receptor matrices and modelled source apportionment. Since usage of biofuels, such as wood, in small combustion units is a globally significant source, this insight may also dramatically change global estimates of organic aerosol emissions.

Description: Impact of planetary boundary layer turbulence on model climate and tracer transport Atmospheric Chemistry and Physics Discussions, 14, 31627-31674, 2014 Author(s): E. L. McGrath-Spangler, A. Molod, L. E. Ott, and S. Pawson Planetary boundary layer (PBL) processes are important for weather, climate, and tracer transport and concentration. One measure of the strength of these processes is the PBL depth. However, no single PBL depth definition exists and several studies have found that the estimated depth can vary substantially based on the definition used. In the Goddard Earth Observing System (GEOS-5) atmospheric general circulation model, the PBL depth is particularly important because it is used to calculate the turbulent length scale that is used in the estimation of turbulent mixing. This study analyzes the impact of using three different PBL depth definitions in this calculation. Two definitions are based on the scalar eddy diffusion coefficient and the third is based on the bulk Richardson number. Over land, the bulk Richardson number definition estimates shallower nocturnal PBLs than the other estimates while over water this definition generally produces deeper PBLs. The near surface wind velocity, temperature, and specific humidity responses to the change in turbulence are spatially and temporally heterogeneous, resulting in changes to tracer transport and concentrations. Near surface wind speed increases in the bulk Richardson number experiment cause Saharan dust increases on the order of 1 × 10 −4 kg m −2 downwind over the Atlantic Ocean. Carbon monoxide (CO) surface concentrations are modified over Africa during boreal summer, producing differences on the order of 20 ppb, due to the model's treatment of emissions from biomass burning. While differences in carbon dioxide (CO 2 ) are small in the time mean, instantaneous differences are on the order of 10 ppm and these are especially prevalent at high latitude during boreal winter. Understanding the sensitivity of trace gas and aerosol concentration estimates to PBL depth is important for studies seeking to calculate surface fluxes based on near-surface concentrations and to studies projecting future concentrations.

Description: Aerosol hygroscopicity and cloud condensation nuclei activity during the AC 3 Exp campaign: implications for cloud condensation nuclei parameterization Atmospheric Chemistry and Physics, 14, 13423-13437, 2014 Author(s): F. Zhang, Y. Li, Z. Li, L. Sun, R. Li, C. Zhao, P. Wang, Y. Sun, X. Liu, J. Li, P. Li, G. Ren, and T. Fan Aerosol hygroscopicity and cloud condensation nuclei (CCN) activity under background conditions and during pollution events are investigated during the Aerosol-CCN-Cloud Closure Experiment (AC 3 Exp) campaign conducted at Xianghe, China in summer 2013. A gradual increase in size-resolved activation ratio (AR) with particle diameter ( D p ) suggests that aerosol particles have different hygroscopicities. During pollution events, the activation diameter ( D a ) measured at low supersaturation (SS) was significantly increased compared to background conditions. An increase was not observed when SS was 〉 0.4%. The hygroscopicity parameter (κ) was ~ 0.31–0.38 for particles in accumulation mode under background conditions. This range in magnitude of κ was ~ 20%, higher than κ derived under polluted conditions. For particles in nucleation or Aitken mode, κ ranged from 0.20–0.34 for background and polluted cases. Larger particles were on average more hygroscopic than smaller particles. The situation was more complex for heavy pollution particles because of the diversity in particle composition and mixing state. A non-parallel observation CCN closure test showed that uncertainties in CCN number concentration estimates ranged from 30–40%, which are associated with changes in particle composition as well as measurement uncertainties associated with bulk and size-resolved CCN methods. A case study showed that bulk CCN activation ratios increased as total condensation nuclei (CN) number concentrations ( N CN ) increased on background days. The background case also showed that bulk AR correlated well with the hygroscopicity parameter calculated from chemical volume fractions. On the contrary, bulk AR decreased with increasing total N CN during pollution events, but was closely related to the fraction of the total organic mass signal at m/z 44 ( f 44 ), which is usually associated with the particle's organic oxidation level. Our study highlights the importance of chemical composition in determining particle activation properties and underlines the significance of long-term observations of CCN under different atmospheric environments, especially regions with heavy pollution.

Description: Factors affecting flood insurance purchase in residential properties in Johor, Malaysia Natural Hazards and Earth System Science, 14, 3297-3310, 2014 Author(s): U. G. Aliagha, T. E. Jin, W. W. Choong, M. Nadzri Jaafar, and H. M. Ali High-impact floods have become a virtually annual experience in Malaysia, yet flood insurance has remained a grossly neglected part of comprehensive integrated flood risk management. Using discriminant analysis, this study seeks to identify the demand-side variables that best predict flood insurance purchase and risk aversion between two groups of residential homeowners in three districts of Johor State, Malaysia: those who purchased flood insurance and those who did not. Our results revealed an overall 34% purchase rate, with Kota Tinggi district having the highest (44%) and thus the highest degree of flood risk aversion. The Wilks' lambda F test for equality of group means, standardised discriminant function coefficients, structure correlation, and canonical correlation has clearly shown that there are strong significant attribute differences between the two groups of homeowners, based on the measures of objective flood risk exposure, subjective risk perception, and socio-economic cum demographic variables. However, the measures of subjective risk perception were found to be more predictive of flood insurance purchase and flood risk aversion.

Description: A century of sea level data and the UK's 2013/14 storm surges: an assessment of extremes and clustering using the Newlyn tide gauge record Ocean Science, 10, 1031-1045, 2014 Author(s): M. P. Wadey, I. D. Haigh, and J. M. Brown For the UK's longest and most complete sea level record (Newlyn), we assess extreme high waters and their temporal clustering; prompted by the 2013/2014 winter of storms and flooding. These are set into context against this almost 100-year record. We define annual periods for which storm activity and high sea levels can be compared on a year-by-year basis. Amongst the storms and high tides which affected Newlyn, the recent winter produced the largest recorded high water level (3 February 2014) and five other high water events above a 1 in 1-year return period. The large magnitude of tide and mean sea level, and the close inter-event spacings (of large return period high waters), suggests that the 2013/2014 extreme high water level "season" can be considered the most extreme on record. However, storm and sea level events may be classified in different ways. For example, in the context of sea level rise (which we calculate linearly as 1.81 ± 0.1 mm yr −1 from records between 1915 to 2014), a lower probability combination of surge and tide occurred on 29 January 1948, whilst the 1995/1996 storm surge season saw the most high waters of ≥ the 1 in 1-year return period. We provide a basic categorisation of the four types of extreme high water level cluster, ranging from consecutive tidal cycles to multiple years. The assessment is extended to other UK sites (with shorter sea level records and different tide-surge characteristics), which suggests 2013/2014 was particularly unusual. Further work will assess clustering mechanisms and flood system "memory".

Description: Derivation and evaluation of landslide-triggering thresholds by a Monte Carlo approach Hydrology and Earth System Sciences, 18, 4913-4931, 2014 Author(s): D. J. Peres and A. Cancelliere Assessment of landslide-triggering rainfall thresholds is useful for early warning in prone areas. In this paper, it is shown how stochastic rainfall models and hydrological and slope stability physically based models can be advantageously combined in a Monte Carlo simulation framework to generate virtually unlimited-length synthetic rainfall and related slope stability factor of safety data, exploiting the information contained in observed rainfall records and field-measurements of soil hydraulic and geotechnical parameters. The synthetic data set, dichotomized in triggering and non-triggering rainfall events, is analyzed by receiver operating characteristics (ROC) analysis to derive stochastic-input physically based thresholds that optimize the trade-off between correct and wrong predictions. Moreover, the specific modeling framework implemented in this work, based on hourly analysis, enables one to analyze the uncertainty related to variability of rainfall intensity within events and to past rainfall (antecedent rainfall). A specific focus is dedicated to the widely used power-law rainfall intensity–duration ( I – D ) thresholds. Results indicate that variability of intensity during rainfall events influences significantly rainfall intensity and duration associated with landslide triggering. Remarkably, when a time-variable rainfall-rate event is considered, the simulated triggering points may be separated with a very good approximation from the non-triggering ones by a I – D power-law equation, while a representation of rainfall as constant–intensity hyetographs globally leads to non-conservative results. This indicates that the I – D power-law equation is adequate to represent the triggering part due to transient infiltration produced by rainfall events of variable intensity and thus gives a physically based justification for this widely used threshold form, which provides results that are valid when landslide occurrence is mostly due to that part. These conditions are more likely to occur in hillslopes of low specific upslope contributing area, relatively high hydraulic conductivity and high critical wetness ratio. Otherwise, rainfall time history occurring before single rainfall events influences landslide triggering, determining whether a threshold based only on rainfall intensity and duration may be sufficient or it needs to be improved by the introduction of antecedent rainfall variables. Further analyses show that predictability of landslides decreases with soil depth, critical wetness ratio and the increase of vertical basal drainage (leakage) that occurs in the presence of a fractured bedrock.

Description: Climate change and stream temperature projections in the Columbia River basin: habitat implications of spatial variation in hydrologic drivers Hydrology and Earth System Sciences, 18, 4897-4912, 2014 Author(s): D. L. Ficklin, B. L. Barnhart, J. H. Knouft, I. T. Stewart, E. P. Maurer, S. L. Letsinger, and G. W. Whittaker Water temperature is a primary physical factor regulating the persistence and distribution of aquatic taxa. Considering projected increases in air temperature and changes in precipitation in the coming century, accurate assessment of suitable thermal habitats in freshwater systems is critical for predicting aquatic species' responses to changes in climate and for guiding adaptation strategies. We use a hydrologic model coupled with a stream temperature model and downscaled general circulation model outputs to explore the spatially and temporally varying changes in stream temperature for the late 21st century at the subbasin and ecological province scale for the Columbia River basin (CRB). On average, stream temperatures are projected to increase 3.5 °C for the spring, 5.2 °C for the summer, 2.7 °C for the fall, and 1.6 °C for the winter. While results indicate changes in stream temperature are correlated with changes in air temperature, our results also capture the important, and often ignored, influence of hydrological processes on changes in stream temperature. Decreases in future snowcover will result in increased thermal sensitivity within regions that were previously buffered by the cooling effect of flow originating as snowmelt. Other hydrological components, such as precipitation, surface runoff, lateral soil water flow, and groundwater inflow, are negatively correlated to increases in stream temperature depending on the ecological province and season. At the ecological province scale, the largest increase in annual stream temperature was within the Mountain Snake ecological province, which is characterized by migratory coldwater fish species. Stream temperature changes varied seasonally with the largest projected stream temperature increases occurring during the spring and summer for all ecological provinces. Our results indicate that stream temperatures are driven by local processes and ultimately require a physically explicit modeling approach to accurately characterize the habitat regulating the distribution and diversity of aquatic taxa.

Description: Monitoring and modelling of soil–plant interactions: the joint use of ERT, sap flow and Eddy Covariance data to characterize the volume of an orange tree root zone Hydrology and Earth System Sciences Discussions, 11, 13353-13384, 2014 Author(s): G. Cassiani, J. Boaga, D. Vanella, M. T. Perri, and S. Consoli Mass and energy exchanges between soil, plants and atmosphere control a number of key environmental processes involving hydrology, biota and climate. The understanding of these exchanges also play a critical role for practical purposes e.g. in precision agriculture. In this paper we present a methodology based on coupling innovative data collection and models in order to obtain quantitative estimates of the key parameters of such complex flow system. In particular we propose the use of hydro-geophysical monitoring via 4-D Electrical Resistivity Tomography (ERT) in conjunction with measurements of plant transpiration via sap flow and evapotranspiration from Eddy Covariance (EC). This abundance of data is fed to a spatially distributed soil model in order to characterize the distribution of active roots. We conducted experiments in an orange orchard in Eastern Sicily (Italy), characterized by the typical Mediterranean semi-arid climate. The subsoil dynamics, particularly influenced by irrigation and root uptake, were characterized mainly by the ERT setup, consisting of 48 buried electrodes on 4 instrumented micro boreholes (about 1.2 m deep) placed at the corners of a square (about 1.3 m in side) surrounding the orange tree, plus 24 mini-electrodes on the surface spaced 0.1 m on a square grid. During the monitoring, we collected repeated ERT and TDR soil moisture measurements, soil water samples, sap flow measurements from the orange tree and EC data. We conducted a laboratory calibration of the soil electrical properties as a function of moisture content and pore water electrical conductivity. Irrigation, precipitation, sap flow and ET data are available allowing knowledge of the system's long term forcing conditions on the system. This information was used to calibrate a 1-D Richards' equation model representing the dynamics of the volume monitored via 3-D ERT. Information on the soil hydraulic properties was collected from laboratory and field experiments. The successful results of the calibrated modeling exercise allow the quantification of the soil volume interested by root water uptake. This volume is much smaller (with a surface area less than 2 m 2 , and about 40 cm thickness) than expected and assumed in the design of classical drip irrigation schemes that prove to be losing at least half of the irrigated water that is not uptaken by the plants.

Description: Energy exchange and wave action conservation for magnetohydrodynamic (MHD) waves in a general, slowly varying medium Annales Geophysicae, 32, 1495-1510, 2014 Author(s): A. D. M. Walker Magnetohydrodynamic (MHD) waves in the solar wind and magnetosphere are propagated in a medium whose velocity is comparable to or greater than the wave velocity and which varies in both space and time. In the approximation where the scales of the time and space variation are long compared with the period and wavelength, the ray-tracing equations can be generalized and then include an additional first-order differential equation that determines the variation of frequency. In such circumstances the wave can exchange energy with the background: wave energy is not conserved. In such processes the wave action theorem shows that the wave action, defined as the ratio of the wave energy to the frequency in the local rest frame, is conserved. In this paper we discuss ray-tracing techniques and the energy exchange relation for MHD waves. We then provide a unified account of how to deal with energy transport by MHD waves in non-uniform media. The wave action theorem is derived directly from the basic MHD equations for sound waves, transverse Alfvén waves, and the fast and slow magnetosonic waves. The techniques described are applied to a number of illustrative cases. These include a sound wave in a medium undergoing a uniform compression, an isotropic Alfvén wave in a steady-state shear layer, and a transverse Alfvén wave in a simple model of the magnetotail undergoing compression. In each case the nature and magnitude of the energy exchange between wave and background is found.

Description: Examining the major contributors and controlling factors of ozone production in a rural area of the Yangtze River Delta region during harvest season Atmospheric Chemistry and Physics Discussions, 14, 30913-30945, 2014 Author(s): X. Pan, Y. Kanaya, H. Tanimoto, S. Inomata, Z. Wang, S. Kudo, and I. Uno Open biomass burning (OBB) has been reported to emit substantial amounts of non-methane hydrocarbons (NMHCs), and the mixing of OBB with urban plumes could exacerbate regional ozone (O 3 ) pollution. In the present study, an observational field campaign was performed in a rural area at the edge of Yangtze River Delta region (YRDR) during harvest season when intensive open burning of wheat residues was observed. The O 3 production rate at the site was calculated using a photochemical box model (Regional Atmospheric Chemical Mechanism, Version 2) constrained by real-time ambient measurements (e.g., O 3 , volatile organic compounds (VOCs), the sum of NO 2 + NO (NO x ), J values). During the period impacted by OBB, the O 3 concentration frequently exceeded 100 ppbv. Analysis showed that the net O 3 production was pronounced, in particular when the site was characterized by a prevailing southerly wind that also brought substantial amounts of NO x emitted from urban areas. At these times, the maximum rate of O 3 production was 20 ppbv h −1 with potential production rate of 102 ppbv on a daily basis. The O 3 production at the site was typically VOC-sensitive in the morning because NO x dominated the plumes. However, in the afternoon, conditions became NO x -sensitive due to the rapid photochemical consumption of NO x in the production of O 3 . A positive matrix factorization analysis indicated that solvent usage and OBB were the primary contributors to the mass fraction of ambient NMHCs observed at the study site, and were responsible for 35 and 23% of the total O 3 production, respectively. The preferential presence of NO x in the morning inhibited net O 3 production; meanwhile O 3 built up in the afternoon due to a decrease in NO x concentrations. These results indicated that a joint effort in the regulation of solvent (aromatics) usage and OBB, as well as NO x from on-road vehicle exhaust may be effective in eliminating high-O 3 pollution risk in the rural areas of the YRDR.

Description: On the use of the post-closure method uncertainty band to evaluate the performance of land surface models against eddy covariance flux data Biogeosciences Discussions, 11, 16911-16951, 2014 Author(s): J. Ingwersen, K. Imukova, P. Högy, and T. Streck The energy balance of eddy covariance (EC) flux data is normally not closed. Therefore, at least if used for modeling, EC flux data are usually post-closed, i.e. the measured turbulent fluxes are adjusted so as to close the energy balance. At the current state of knowledge, however, it is not clear how to partition the missing energy in the right way. Eddy flux data therefore contain some uncertainty due to the unknown nature of the energy balance gap, which should be considered in model evaluation and the interpretation of simulation results. We propose to construct the post-closure method uncertainty band (PUB), which essentially designates the differences between non-adjusted flux data and flux data adjusted with the three post-closure methods (Bowen ratio, latent heat flux (LE) and sensible heat flux ( H ) method). To demonstrate this approach, simulations with the NOAH-MP land surface model were evaluated based on EC measurements conducted at a winter wheat stand in Southwest Germany in 2011, and the performance of the Jarvis and Ball–Berry stomatal resistance scheme was compared. The width of the PUB of the LE was up to 110 W m –2 (21% of net radiation). Our study shows that it is crucial to account for the uncertainty of EC flux data originating from lacking energy balance closure. Working with only a single post-closing method might result in severe misinterpretations in model-data comparisons.

Description: Carbon, oxygen and biological productivity in the Southern Ocean in and out the Kerguelen plume: CARIOCA drifter results Biogeosciences Discussions, 11, 16877-16909, 2014 Author(s): L. Merlivat, J. Boutin, and F. d'Ovidio The Kerguelen Plateau region in the Indian sector of the Southern Ocean supports annually a large-scale phytoplankton bloom which is naturally fertilized with iron. As part of the second Kerguelen Ocean and Plateau compared Study expedition (KEOPS2) in austral spring (October–November 2011), one Carioca buoy was deployed east of the Kerguelen plateau. It drifted eastward downstream in the Kerguelen plume. Hourly surface measurements of p CO 2 , O 2 and ancillary observations were collected between 1 November 2011 to 12 February 2012 with the aim of characterizing the spatial and temporal variability of the biological Net Community Production (NCP) downstream the Kerguelen plateau, assess the impact of iron-induced productivity on the biological carbon consumption and consequently on the CO 2 flux exchanged at the air–sea interface. The trajectory of the buoy until mid-December was within the longitude range, 72–83° E, close to the polar front and then in the polar frontal zone, PFZ, until 97° E. From 17 November to 16 December, the buoy drifted within the Kerguelen plume following a filament carrying dissolved iron, DFe, for a total distance of 700 km. In the first part of the trajectory, the ocean surface waters are a sink for CO 2 and a source for CO 2 , with fluxes of respective mean values equal to −8 and +38 mmol CO 2 m −2 d −1 . Eastward, as the buoy escapes the iron enriched filament, the fluxes are in opposite direction, with respective mean values of +5 and −48 mmol O 2 m −2 d −1 . These numbers clearly indicate the strong impact of biological processes on the biogeochemistry in the surface waters within the Kerguelen plume in November-mid-December, while it is undetectable eastward in the PFZ from mid-December to mid-February. While the buoy follows the Fe enriched filament, simultaneous observations of dissolved inorganic carbon, DIC, and dissolved oxygen, O 2 , highlight biological events lasting from 2 to 4 days. Stoichiometric ratios, O 2 /C, between 1.1 and 1.4 are observed indicating new and regenerated production regimes. NCP estimates range from 60 to 140 mmol C m −2 d −1 . Based on the relationship between the time a water parcel has left the plateau and its iron content, we have highlighted that the main control on the value of NCP is the availability of iron in the upper water column, with the largest NCP occurring in waters that have recently left the plateau and presented the highest iron concentrations.

Description: Comparison of UV/Vis and FDOM sensors for in situ monitoring of stream DOC concentrations Biogeosciences Discussions, 11, 16855-16876, 2014 Author(s): G.-Y. Yoo, Y. Jeong, E.-J. Lee, J.-H. Park, and N.-H. Oh Optical measurements using ultra-violet/visible (UV/Vis) spectrophotometric sensors and fluorescent dissolved organic matter (FDOM) sensors have recently been used as proxies of dissolved organic carbon (DOC) concentrations of streams and rivers at high temporal resolution. Despite of the merits of the sensors, temperature changes and particulate matter in water can interfere the sensor readings, over- or under-estimating DOC concentrations. However, little efforts have been made to compare responses of the two types of the sensors in natural conditions. We conducted both laboratory experiments and in situ monitoring with a UV/Vis sensor and a FDOM sensor during the three storm events in the fall of 2012 and the spring of 2013 in a forest stream in Korea in order to compare their performance. Laboratory experiments using the Suwannee River natural organic matter, humic acid, and fulvic acid demonstrated strong linear relationships between both the sensor signals and measured DOC concentrations with R 2 ≥ 0.98. Although temperature compensation might not be needed for the UV/Vis sensor, it was sensitive to relativley small changes in turbidity. In contrast, the FDOM sensor was insenstive to relatively low turbidity while the FDOM sensor outputs decreased significantly as temperature increased, requiring temperature compensated FDOM (e.g. FDOM 20 for 20 °C) for in situ monitoring of DOC. The results suggest that both sensors can be employed as a~proxy for stream DOC concentrations after temperature and turbidity compensation in a forest stream where terrestrially derived humic-like materials are dominant components.

Description: Modeling the impact of riverine DON removal by marine bacterioplankton on primary production in the Arctic Ocean Biogeosciences Discussions, 11, 16953-16992, 2014 Author(s): V. Le Fouest, M. Manizza, B. Tremblay, and M. Babin The planktonic and biogeochemical dynamics of the Arctic shelves exhibit a strong variability in response to Arctic warming. In this study, in order to elucidate on the processes regulating the production of phytoplankton (PP) and bacterioplankton (BP) and their interactions, we employ a biogeochemical model coupled to a pan-Arctic ocean-sea ice model (MITgcm) to explicitly simulate and quantify the contribution of usable dissolved organic nitrogen (DON) drained by the major circum-Arctic rivers on PP and BP in a scenario of melting sea ice (1998–2011). Model simulations suggest that on average between 1998 and 2011, the removal of usable RDON by bacterioplankton is responsible of a ~26% increase of the annual BP for the whole Arctic Ocean. With respect to total PP, the model simulates an increase of ~8% on an annual basis and of ~18% in summer. Recycled ammonium is responsible for the PP increase. The recycling of RDON by bacterioplankton promotes higher BP and PP but there is no significant temporal trend in the BP : PP ratio within the ice-free shelves over the 1998–2011 period. This suggests no significant evolution in the balance between autotrophy and heterotrophy in the last decade with a constant annual flux of RDON into the coastal ocean although changes in RDON supply and further reduction in sea ice cover could potentially alter this delicate balance.

Description: The double layers in the plasma sheet boundary layer during magnetic reconnection Nonlinear Processes in Geophysics Discussions, 1, 1657-1671, 2014 Author(s): J. Guo and B. Yu We studied the evolutions of double layers which appear after the magnetic reconnection through two-dimensional electromagnetic particle-in-cell simulation. The simulation results show that the double layers are formed in the plasma sheet boundary layer after magnetic reconnection. At first, the double layers which have unipolar structures are formed. And then the double layers turn into bipolar structures, which will couple with another new weak bipolar structure. Thus a new double layer or tripolar structure comes into being. The double layers found in our work are about several ten Debye lengths, which accords with the observation results. It is suggested that the electron beam formed during the magnetic reconnection is responsible for the production of the double layers.

Description: 〈b〉Ensemble forecasts of air quality in eastern China – Part 1: Model description and implementation of the MarcoPolo–Panda prediction system, version 1〈/b〉〈br〉 Guy P. Brasseur, Ying Xie, Anna Katinka Petersen, Idir Bouarar, Johannes Flemming, Michael Gauss, Fei Jiang, Rostislav Kouznetsov, Richard Kranenburg, Bas Mijling, Vincent-Henri Peuch, Matthieu Pommier, Arjo Segers, Mikhail Sofiev, Renske Timmermans, Ronald van der A, Stacy Walters, Jianming Xu, and Guangqiang Zhou〈br〉 Geosci. Model Dev., 12, 33-67, https://doi.org/10.5194/gmd-12-33-2019, 2019〈br〉 An operational multi-model forecasting system for air quality provides daily forecasts of ozone, nitrogen oxides, and particulate matter for 37 urban areas in China. The paper presents an intercomparison of the different forecasts performed during a specific period of time and highlights recurrent differences between the model output. Pathways to improve the forecasts by the multi-model system are suggested.

Description: 〈b〉RandomFront 2.3: a physical parameterisation of fire spotting for operational fire spread models – implementation in WRF-SFIRE and response analysis with LSFire+〈/b〉〈br〉 Andrea Trucchia, Vera Egorova, Anton Butenko, Inderpreet Kaur, and Gianni Pagnini〈br〉 Geosci. Model Dev., 12, 69-87, https://doi.org/10.5194/gmd-12-69-2019, 2019〈br〉 Wildfires are a concrete problem and impact on human life, property and the environment. An extremely dangerous phenomenon is so-called 〈q〉fire spotting〈/q〉, i.e., the generation of secondary ignitions responsible for dangerous flare-ups during wildfires. The aim of this research was to improve the tools used for risk management through the inclusion of fire spotting in operational wildfire simulators used by forest service agencies.

Description: 〈b〉Vertical characterization of aerosol optical properties and brown carbon in winter in urban Beijing, China〈/b〉〈br〉 Conghui Xie, Weiqi Xu, Junfeng Wang, Qingqing Wang, Dantong Liu, Guiqian Tang, Ping Chen, Wei Du, Jian Zhao, Yingjie Zhang, Wei Zhou, Tingting Han, Qingyun Bian, Jie Li, Pingqing Fu, Zifa Wang, Xinlei Ge, James Allan, Hugh Coe, and Yele Sun〈br〉 Atmos. Chem. Phys., 19, 165-179, https://doi.org/10.5194/acp-19-165-2019, 2019〈br〉 We present the first simultaneous real-time online measurements of aerosol optical properties at ground level and at 260 m on a meteorological tower in urban Beijing in winter. The vertical similarities and differences in scattering and absorption coefficients were characterized. The increases in MAC of BC were mainly associated with the coating materials on rBC. Coal combustion was the dominant source contribution of brown carbon followed by biomass burning and SOA in winter in Beijing.

Description: 〈b〉Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging〈/b〉〈br〉 Chunlin Li, Quanfu He, Julian Schade, Johannes Passig, Ralf Zimmermann, Daphne Meidan, Alexander Laskin, and Yinon Rudich〈br〉 Atmos. Chem. Phys., 19, 139-163, https://doi.org/10.5194/acp-19-139-2019, 2019〈br〉 〈p〉Following wood pyrolysis, tar ball aerosols were laboratory generated from wood tar separated into polar and nonpolar phases. Chemical information of fresh tar balls was obtained from a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and single-particle laser desorption/resonance enhanced multiphoton ionization mass spectrometry (SP-LD-REMPI-MS). Their continuous refractive index (RI) between 365 and 425 nm was retrieved using a broadband cavity enhanced spectroscopy (BBCES). Dynamic changes in the optical and chemical properties for the nonpolar tar ball aerosols in 〈span〉NO〈sub〉〈i〉x〈/i〉〈/sub〉〈/span〉-dependent photochemical process were investigated in an oxidation flow reactor (OFR). Distinct differences in the chemical composition of the fresh polar and nonpolar tar aerosols were identified. Nonpolar tar aerosols contain predominantly high-molecular weight unsubstituted and alkyl-substituted polycylic aromatic hydrocarbons (PAHs), while polar tar aerosols consist of a high number of oxidized aromatic substances (e.g., methoxy-phenols, benzenediol) with higher O : C ratios and carbon oxidation states. Fresh tar balls have light absorption characteristics similar to atmospheric brown carbon (BrC) aerosol with higher absorption efficiency towards the UV wavelengths. The average retrieved RI is 〈span〉1.661+0.020〈i〉i〈/i〉〈/span〉 and 〈span〉1.635+0.003〈i〉i〈/i〉〈/span〉 for the nonpolar and polar tar aerosols, respectively, with an absorption Ångström exponent (AAE) between 5.7 and 7.8 in the detected wavelength range. The RI fits a volume mixing rule for internally mixed nonpolar/polar tar balls. The RI of the tar ball aerosols decreased with increasing wavelength under photochemical oxidation. Photolysis by UV light (254 nm), without strong oxidants in the system, slightly decreased the RI and increased the oxidation state of the tar balls. Oxidation under varying OH exposure levels and in the absence of 〈span〉NO〈sub〉〈i〉x〈/i〉〈/sub〉〈/span〉 diminished the absorption (bleaching) and increased the O : C ratio of the tar balls. The photobleaching via OH radical initiated oxidation is mainly attributed to decomposition of chromophoric aromatics, nitrogen-containing organics, and high-molecular weight components in the aged particles. Photolysis of nitrous oxide (〈span〉N〈sub〉2〈/sub〉O〈/span〉) was used to simulate 〈span〉NO〈sub〉〈i〉x〈/i〉〈/sub〉〈/span〉-dependent photochemical aging of tar balls in the OFR. Under high-〈span〉NO〈sub〉〈i〉x〈/i〉〈/sub〉〈/span〉 conditions with similar OH exposure, photochemical aging led to the formation of organic nitrates, and increased both oxidation degree and light absorption for the aged tar ball aerosols. These observations suggest that secondary organic nitrate formation counteracts the bleaching by OH radical photooxidation to eventually regain some absorption of the aged tar ball aerosols. The atmospheric implication and climate effects from tar balls upon various oxidation processes are briefly discussed.〈/p〉

Description: 〈b〉Atmospheric new particle formation in China〈/b〉〈br〉 Biwu Chu, Veli-Matti Kerminen, Federico Bianchi, Chao Yan, Tuukka Petäjä, and Markku Kulmala〈br〉 Atmos. Chem. Phys., 19, 115-138, https://doi.org/10.5194/acp-19-115-2019, 2019〈br〉 The characteristics of new particle formation (NPF) in China, including frequency, formation rate, and particle growth rate, were summarized comprehensively and were compared among observations in different environments. The interactions between air pollution and NPF are discussed, as well as the possible reasons for more frequent NPF under heavy pollution conditions than in our current understanding. Significant and future research directions for NPF studies in China are also summarized.

Description: 〈b〉Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging〈/b〉〈br〉 Chunlin Li, Quanfu He, Julian Schade, Johannes Passig, Ralf Zimmermann, Daphne Meidan, Alexander Laskin, and Yinon Rudich〈br〉 Atmos. Chem. Phys., 19, 139-163, https://doi.org/10.5194/acp-19-139-2019, 2019〈br〉 〈p〉Following wood pyrolysis, tar ball aerosols were laboratory generated from wood tar separated into polar and nonpolar phases. Chemical information of fresh tar balls was obtained from a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and single-particle laser desorption/resonance enhanced multiphoton ionization mass spectrometry (SP-LD-REMPI-MS). Their continuous refractive index (RI) between 365 and 425 nm was retrieved using a broadband cavity enhanced spectroscopy (BBCES). Dynamic changes in the optical and chemical properties for the nonpolar tar ball aerosols in 〈span〉NO〈sub〉〈i〉x〈/i〉〈/sub〉〈/span〉-dependent photochemical process were investigated in an oxidation flow reactor (OFR). Distinct differences in the chemical composition of the fresh polar and nonpolar tar aerosols were identified. Nonpolar tar aerosols contain predominantly high-molecular weight unsubstituted and alkyl-substituted polycylic aromatic hydrocarbons (PAHs), while polar tar aerosols consist of a high number of oxidized aromatic substances (e.g., methoxy-phenols, benzenediol) with higher O : C ratios and carbon oxidation states. Fresh tar balls have light absorption characteristics similar to atmospheric brown carbon (BrC) aerosol with higher absorption efficiency towards the UV wavelengths. The average retrieved RI is 〈span〉1.661+0.020〈i〉i〈/i〉〈/span〉 and 〈span〉1.635+0.003〈i〉i〈/i〉〈/span〉 for the nonpolar and polar tar aerosols, respectively, with an absorption Ångström exponent (AAE) between 5.7 and 7.8 in the detected wavelength range. The RI fits a volume mixing rule for internally mixed nonpolar/polar tar balls. The RI of the tar ball aerosols decreased with increasing wavelength under photochemical oxidation. Photolysis by UV light (254 nm), without strong oxidants in the system, slightly decreased the RI and increased the oxidation state of the tar balls. Oxidation under varying OH exposure levels and in the absence of 〈span〉NO〈sub〉〈i〉x〈/i〉〈/sub〉〈/span〉 diminished the absorption (bleaching) and increased the O : C ratio of the tar balls. The photobleaching via OH radical initiated oxidation is mainly attributed to decomposition of chromophoric aromatics, nitrogen-containing organics, and high-molecular weight components in the aged particles. Photolysis of nitrous oxide (〈span〉N〈sub〉2〈/sub〉O〈/span〉) was used to simulate 〈span〉NO〈sub〉〈i〉x〈/i〉〈/sub〉〈/span〉-dependent photochemical aging of tar balls in the OFR. Under high-〈span〉NO〈sub〉〈i〉x〈/i〉〈/sub〉〈/span〉 conditions with similar OH exposure, photochemical aging led to the formation of organic nitrates, and increased both oxidation degree and light absorption for the aged tar ball aerosols. These observations suggest that secondary organic nitrate formation counteracts the bleaching by OH radical photooxidation to eventually regain some absorption of the aged tar ball aerosols. The atmospheric implication and climate effects from tar balls upon various oxidation processes are briefly discussed.〈/p〉

Description: 〈b〉Watershed classification for the Canadian prairie〈/b〉〈br〉 Jared D. Wolfe, Kevin R. Shook, Chris Spence, and Colin J. Whitfield〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-625,2019〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Watershed classification can identify regions expected to respond similarly to disturbance. Methods should extend beyond hydrology to include other environmental questions, such as ecology and water quality. We developed a classification for the Canadian Prairie, and identified seven classes defined by watershed characteristics, including elevation, climate, wetland density, and surficial geology. Results provide a basis for evaluating watershed response to land management and climate condition.

Description: 〈b〉Implications of water management representations for watershed hydrologic modeling in the Yakima River basin〈/b〉〈br〉 Jiali Qiu, Qichun Yang, Xuesong Zhang, Maoyi Huang, Jennifer C. Adam, and Keyvan Malek〈br〉 Hydrol. Earth Syst. Sci., 23, 35-49, https://doi.org/10.5194/hess-23-35-2019, 2019〈br〉 Complex water management activities challenge hydrologic modeling. We evaluated how different representations of reservoir operation and agricultural irrigation affect streamflow simulations in the Yakima River basin. Results highlight the importance of the inclusion of reliable reservoir and irrigation information in watershed models for improving watershed hydrology modeling. Models used here are public and hold the promise to benefit water assessment and management in other basins.

Description: 〈b〉Aircraft-based measurements of High Arctic springtime aerosol show evidence for vertically varying sources, transport and composition〈/b〉〈br〉 Megan D. Willis, Heiko Bozem, Daniel Kunkel, Alex K. Y. Lee, Hannes Schulz, Julia Burkart, Amir A. Aliabadi, Andreas B. Herber, W. Richard Leaitch, and Jonathan P. D. Abbatt〈br〉 Atmos. Chem. Phys., 19, 57-76, https://doi.org/10.5194/acp-19-57-2019, 2019〈br〉 The vertical distribution of Arctic aerosol is an important driver of its climate impacts. We present vertically resolved measurements of aerosol composition and properties made in the High Arctic during spring on an aircraft platform. We explore how aerosol properties are related to transport history and show evidence of vertical trends in aerosol sources, transport mechanisms and composition. These results will help us to better understand aerosol–climate interactions in the Arctic.

Description: 〈b〉Estimating the soil N〈sub〉2〈/sub〉O emission intensity of croplands in northwest Europe〈/b〉〈br〉 Vasileios Myrgiotis, Mathew Williams, Robert M. Rees, and Cairistiona F. E. Topp〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-490,2019〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 This study focuses on a northwest European cropland region and shows that the type of crop growing on a soil has notable effects on the emission of nitrous oxide (N〈sub〉2〈/sub〉O – a greenhouse gas) from that soil. It was found that N〈sub〉2〈/sub〉O emissions from soils under oilseed cultivation are significantly higher than soils under cereal cultivation. This variation is mostly explained by the fact that oilseeds require more nitrogen (fertiliser) than cereals especially at early crop growth stages.

Description: 〈b〉A Double ITCZ Phenomenology of Wind Errors in the Equatorial Atlantic in Seasonal Forecasts with ECMWF Models〈/b〉〈br〉 Jonathan K. P. Shonk, Teferi D. Demissie, and Thomas Toniazzo〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1316,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 Modern climate models are affected by systematic biases that harm their ability to produce reliable seasonal forecasts and climate projections. In this study, we investigate causes of biases in wind patterns over the tropical Atlantic during northern spring in three related models. We find that the wind biases are associated with an increase in excess rainfall and convergence in the tropical western Atlantic at the start of April, leading to the redirection of trade winds away from the equator.

Description: 〈b〉Spiky Fluctuations and Scaling in High-Resolution EPICA Ice Core Dust Fluxes〈/b〉〈br〉 Shaun Lovejoy and Fabrice Lambert〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-171,2019〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 0 comments)〈br〉 We analyze the statistical properties of the eight past glacial-interglacial cycles as well as subsections of a generic glacial cycle using the high-resolution dust flux dataset from the Antarctic EPICA Dome C ice core. We show that the high southern latitude climate during glacial maxima, interglacial, and glacial inception is generally more stable but more drought-prone than during mid-glacial conditions.

Description: 〈b〉Nutrient distribution and nitrogen and oxygen isotopic composition of nitrate in water masses of the subtropical South Indian Ocean〈/b〉〈br〉 Natalie C. Harms, Niko Lahajnar, Birgit Gaye, Tim Rixen, Kirstin Dähnke, Markus Ankele, Ulrich Schwarz-Schampera, and Kay-Christian Emeis〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-511,2019〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 The Indian Ocean subtropical gyre is a large oligotrophic area that is likely to adjust to continued warming by increasing stratification, reduced nutrient supply, and decreasing biological production. In this study, we investigated concentrations of nutrients and stable isotopes of nitrate. We determine the lateral influence of water masses entering the gyre from the northern Indian Ocean and from the Southern Ocean and quantify the input of nitrogen by N〈sub〉2〈/sub〉-fixation into the surface layer.

Description: 〈b〉New particle formation in the marine atmosphere during seven cruise campaigns〈/b〉〈br〉 Yujiao Zhu, Kai Li, Yanjie Shen, Yang Gao, Xiaohuan Liu, Yang Yu, Huiwang Gao, and Xiaohong Yao〈br〉 Atmos. Chem. Phys., 19, 89-113, https://doi.org/10.5194/acp-19-89-2019, 2019〈br〉 In this paper, we investigate new particle formation (NPF) events during seven cruises. NPF events were observed on 25 days and were most likely associated with the long-range transport of anthropogenic air pollutants. The relationship between the net generated amount of new particles and their apparent formation rate is established and explained in terms of the roles of different vapor precursors. The survival probability of new particles to CCN size is also discussed.

Description: 〈b〉Aircraft-based measurements of High Arctic springtime aerosol show evidence for vertically varying sources, transport and composition〈/b〉〈br〉 Megan D. Willis, Heiko Bozem, Daniel Kunkel, Alex K. Y. Lee, Hannes Schulz, Julia Burkart, Amir A. Aliabadi, Andreas B. Herber, W. Richard Leaitch, and Jonathan P. D. Abbatt〈br〉 Atmos. Chem. Phys., 19, 57-76, https://doi.org/10.5194/acp-19-57-2019, 2019〈br〉 The vertical distribution of Arctic aerosol is an important driver of its climate impacts. We present vertically resolved measurements of aerosol composition and properties made in the High Arctic during spring on an aircraft platform. We explore how aerosol properties are related to transport history and show evidence of vertical trends in aerosol sources, transport mechanisms and composition. These results will help us to better understand aerosol–climate interactions in the Arctic.

Description: 〈b〉Simulated single-layer forest canopies delay Northern Hemisphere snowmelt〈/b〉〈br〉 Markus Todt, Nick Rutter, Christopher G. Fletcher, and Leanne M. Wake〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-270,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Vegetation is often represented by a single layer in global land models. Studies have found deficient simulation of thermal radiation beneath forest canopies when represented by single-layer vegetation. This study corrects thermal radiation in forests for a global land model using single-layer vegetation in order to assess the effect of deficient thermal radiation on snow cover and snowmelt. Results indicate that single-layer vegetation causes snow in forests being too cold and melting too late.

Description: 〈b〉Brief Communication: Early season snowpack loss and implications for oversnow vehicle recreation travel planning〈/b〉〈br〉 Benjamin J. Hatchett and Hilary G. Eisen〈br〉 The Cryosphere, 13, 21-28, https://doi.org/10.5194/tc-13-21-2019, 2019〈br〉 We examine the timing of early season snowpack relevant to oversnow vehicle (OSV) recreation over the past 3 decades in the Lake Tahoe region (USA). Data from two independent data sources suggest that the timing of achieving sufficient snowpack has shifted later by 2 weeks. Increasing rainfall and more dry days play a role in the later onset. Adaptation strategies are provided for winter travel management planning to address negative impacts of loss of early season snowpack for OSV usage.

Description: 〈b〉Aerosol radiative effects with MACv2〈/b〉〈br〉 Stefan Kinne〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-949,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉onthly global maps for aerosol properties of the MACv2 climatology are applied in an off-line radiative transfer model to determine aerosol radiative effects. For details beyond global averages in most cases global maps are presented to visualize regional and seasonal details. Aside from the direct radiative (aerosol presence) effect, including those for aerosol components as extracted from MACv2 aerosol optics, also the major aerosol indirect radiative effect is covered. Hereby, the impact of smaller drops in water clouds due to added anthropogenic aerosol was simulated by applying a satellite retrieval based fit from locally associations between aerosol and drop concentrations over oceans. Present-day anthropogenic aerosols of MACv2 – on a global average basis – reduce the radiative net-fluxes at the top of the atmosphere (TOA) by −1.0 W/m〈sup〉2〈/sup〉 and at the surface by −2.1 W/m〈sup〉2〈/sup〉. Direct cooling contributions are only about half of indirect contributions (−.35 vs −.65) at TOA, but about twice at the surface (−1.45 vs −.65), as solar absorption of the direct effect warms the atmosphere by +1.1 W/m〈sup〉2〈/sup〉. Natural aerosols are on average less absorbing (for a relatively larger solar TOA cooling) and larger in size (now contributing with IR greenhouse warming). Thus, average TOA direct forcing efficiencies for total and anthropogenic aerosol happen to be similar: −11 W/m〈sup〉2〈/sup〉/AOD at all-sky and −24 W/m〈sup〉2〈/sup〉/AOD at clear-sky conditions. The present-day direct impact by all soot (BC) is globally averaged +0.55W/m〈sup〉2〈/sup〉 and at least half of it should be attributed to anthropogenic sources. Hereby any accuracy of anthropogenic impacts, not just for soot, suffers from the limited access to a pre-industrial reference. Anthropogenic uncertainty has a particular strong impact on aerosol indirect effects, which dominate the (TOA) forcing. Accounting for uncertainties in the anthropogenic definition, present-day aerosol forcing is estimated to stay within the −0.7 to −1.6 W/m〈sup〉2〈/sup〉 range, with a best estimate at −1 W/m〈sup〉2〈/sup〉. Calculations with model predicted temporal changes to anthropogenic AOD indicate that qualitatively the anthropogenic aerosol forcing has not changed much over the last decades and is not likely to increase over the next decades, despite strong regional shifts. These regional shifts explain most solar insolation (brightening or dimming) trends that have been observed by ground-based radiation data.〈/p〉

Description: 〈b〉Thermal structure of the mesopause region during the WADIS-2 rocket campaign〈/b〉〈br〉 Raimund Wörl, Boris Strelnikov, Timo P. Viehl, Josef Höffner, Pierre-Dominique Pautet, Michael J. Taylor, Yucheng Zhao, and Franz-Josef Lübken〈br〉 Atmos. Chem. Phys., 19, 77-88, https://doi.org/10.5194/acp-19-77-2019, 2019〈br〉 Simultaneous temperature measurements during the WADIS-2 rocket campaign are used to investigate the thermal structure of the mesopause region. Vertically and horizontally resolved in situ and remote measurements are in good agreement and show dominating long-term and large-scale waves with periods of 24 h and higher tidal harmonics. Only a few gravity waves with periods shorter than 6 h and small amplitudes are there.

Description: 〈b〉Verification of anthropogenic VOC emission inventory through ambient measurements and satellite retrievals〈/b〉〈br〉 Jing Li, Yufang Hao, Maimaiti Simayi, Yuqi Shi, Ziyan Xi, and Shaodong Xie〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1133,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 We established an emission inventory of anthropogenic VOCs in the Beijing–Tianjin–Hebei region of China. The developed emission inventory was evaluated through ambient measurements and satellite retrieval results. To obtain a more accurate emission inventory, we propose the investigation of the household coal consumption, the adjustment of EFs based on the latest pollution control policies, and the verification of the source profiles of OVOCs and halocarbons.

Description: 〈b〉Classification of aerosol population type and cloud condensation nuclei properties in a coastal California littoral environment using an unsupervised cluster model〈/b〉〈br〉 Samuel A. Atwood, Sonia M. Kreidenweis, Paul J. DeMott, Markus D. Petters, Gavin C. Cornwell, Andrew C. Martin, and Kathryn A. Moore〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1297,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 This paper presents measurements of aerosol particles at a coastal location. The particles were classified into distinct aerosol types using both microphysical measurements and meteorological information, allowing rapid changes between the aerosol types to be reliably identified. These particles can alter cloud and precipitation processes, and inclusion of the differences between types can improve atmospheric models and remote sensing retrievals in littoral zones.

Description: 〈b〉Development of a balloon-borne instrument for CO〈sub〉2〈/sub〉 vertical profile observations in the troposphere〈/b〉〈br〉 Mai Ouchi, Yutaka Matsumi, Tomoki Nakayama, Kensaku Shimizu, Takehiko Sawada, Toshinobu Machida, Hidekazu Matsueda, Yousuke Sawa, Isamu Morino, Osamu Uchino, Tomoaki Tanaka, and Ryoichi Imasu〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-376,2019〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 A novel, practical observation system for measuring tropospheric carbon dioxide (CO〈sub〉2〈/sub〉) concentrations carried by a small helium-filled balloon (CO〈sub〉2〈/sub〉 sonde), has been developed for the first time. The low-cost CO〈sub〉2〈/sub〉 sondes can potentially be used for frequently measurements of vertical profiles of CO〈sub〉2〈/sub〉 in any parts of the world providing as useful information to understand the global and regional carbon budgets by replenishing the present sparse observation coverage.

Description: 〈b〉Comparison of Different Sequential Assimilation Algorithms for Satellite-derived Leaf Area Index Using the Data Assimilation Research Testbed (lanai)〈/b〉〈br〉 Xiao-Lu Ling, Cong-Bin Fu, Zong-Liang Yang, and Wei-Dong Guo〈br〉 Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2018-232,2019〈br〉 〈b〉Manuscript under review for GMD〈/b〉 (discussion: open, 0 comments)〈br〉 Both observation and simulation can provide the temporal and spatial variation of vegetation characteristic, while they are not satisfactory for understanding the mechanism of the exchange between ecosystems and atmosphere. Data assimilation (DA) can combine the observation and models via mathematical statistical analysis.The results show that the Ensemble Adjust Kalman Filter (EAKF) is the optical algorithm. In addition, models perform better when the DA accept more proportion of observation.

Description: 〈b〉The importance of crystalline phases in ice nucleation by volcanic ash〈/b〉〈br〉 Elena C. Maters, Donald B. Dingwell, Corrado Cimarelli, Dirk Müller, Thomas F. Whale, and Benjamin J. Murray〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1326,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 This experimental study investigates the influence of volcanic ash chemical composition, crystallinity, and mineralogy on its ability to promote freezing of supercooled water. The results indicate that crystals in ash play a key role in this process, and suggest that alkali and plagioclase feldspars in ash may be highly ice-active. These findings contribute to improving understanding of the potential of ash emissions from different explosive eruptions to impact ice formation in the atmosphere.

Description: 〈b〉Large increases in N〈sub〉cn〈/sub〉 and N〈sub〉ccn〈/sub〉 together with a nucleation-modeparticle pool over the northwestern Pacific Ocean in the spring of 2014〈/b〉〈br〉 Juntao Wang, Yanjie Shen, Kai Li, Yang Gao, Huiwang Gao, and Xiaohong Yao〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1089,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 In this paper, we studied the spatiotemporal variability of N〈sub〉cn〈/sub〉 and particle number size distributions, as well as N〈sub〉ccn〈/sub〉 and CCN activities over the NWPO in the spring of 2014. Several new findings have been revealed and discussed, e.g., large increases of N〈sub〉cn〈/sub〉 and N〈sub〉ccn〈/sub〉, against historical data and small contributions of dust and BB aerosols to N〈sub〉cn〈/sub〉 and N〈sub〉ccn〈/sub〉 on the monthly time scale, etc. This work may help understand the influence of the current outflow from the Asian continent on the climate.

Description: 〈b〉Analyses of temperature and precipitation in the Indian Jammu and Kashmir region for the 1980–2016 period: implications for remote influence and extreme events〈/b〉〈br〉 Sumira Nazir Zaz, Shakil Ahmad Romshoo, Ramkumar Thokuluwa Krishnamoorthy, and Yesubabu Viswanadhapalli〈br〉 Atmos. Chem. Phys., 19, 15-37, https://doi.org/10.5194/acp-19-15-2019, 2019〈br〉 This paper is of first of its kind for the Jammu and Kashmir (western Himalayas) region, India. It shows the clear relation between the upper tropospheric Rossby wave activity (potential vorticity at the 350 K potential temperature and 200 mb level surface pressure) and the surface weather parameters (e.g., precipitation) over a period of 3 decades during 1980–2016. This indicates that the climatic weather pattern over the Kashmir region is influenced mostly by global climate change processes.

Description: 〈b〉Secondary organic aerosol formation from smoldering and flaming combustion of biomass: a box model parametrization based on volatility basis set〈/b〉〈br〉 Giulia Stefenelli, Jianhui Jiang, Amelie Bertrand, Emily A. Bruns, Simone M. Pieber, Urs Baltensperger, Nicolas Marchand, Sebnem Aksoyoglu, André S. H. Prévôt, Jay G. Slowik, and Imad El Haddad〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1308,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 Box model simulations, based on the volatility basis set (VBS) approach, of smog chamber wood combustion experiments conducted at different temperatures (−10 °C, 2 °C, 15 °C), emission loads, combustion conditions (flaming and smoldering) and residential stoves fabricated in the last two decades. Novel parameterization methods based on a genetic algorithm approach allowed estimation of precursor class contributions to SOA and evaluation of the effect of emission variability on SOA yield predictions.

Description: 〈b〉Impacts of Horizontal Resolution and Air–Sea Flux Parameterization on the Intensity and Structure of simulated Typhoon Haiyan (2013)〈/b〉〈br〉 Mien-Tze Kueh, Wen-Mei Chen, Yang-Fan Sheng, Simon C. Lin, Tso-Ren Wu, Eric Yen, Yu-Lin Tsai, and Chuan-Yao Lin〈br〉 Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2018-333,2019〈br〉 〈b〉Manuscript under review for NHESS〈/b〉 (discussion: open, 0 comments)〈br〉 In this study, we show that both the model horizontal resolution and air-sea flux parameterization can exert large influence on tropical cyclone intensity simulation but with different impacts on wind structures. We highlight the intensification and contraction of TC eyewall in response to the reduction of grid spacing. We also suggest that a well-developed eyewall is more conducive to the positive effect of flux formulas on TC development.

Description: 〈b〉Primary and secondary sources of ambient formaldehyde in the Yangtze River Delta based on OMPS observation〈/b〉〈br〉 Wenjing Su, Cheng Liu, Qihou Hu, Shaohua Zhao, Youwen Sun, Wei Wang, Yizhi Zhu, Jianguo Liu, and Jhoon Kim〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1192,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 For a better understanding of the pollution and atmospheric chemistry of HCHO, we evaluated its primary and secondary sources in the Yangtze River Delta based on HCHO column density from Ozone Mapping and Profiler Suite (OMPS) and combining with surface in-situ measurements. We found that secondary formation contributed most to ambient HCHO for a long time, but primary emission could be dominant in the winter. The usability of total HCHO as the proxy of VOCs reactivity depends on time scale.

Description: 〈b〉Local and regional contributions to fine particulate matter in the 18 cities of Sichuan Basin, southwestern China〈/b〉〈br〉 Xue Qiao, Hao Guo, Ya Tang, Pengfei Wang, Wenye Deng, Xing Zhao, Jianlin Hu, Qi Ying, and Hongliang Zhang〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1214,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 A source-oriented version of the CMAQ model was used to quantify contributions from nine regions to PM〈sub〉2.5〈/sub〉 and its components in the 18 cities within the Sichuan Basin. Non-local emissions contribute to 39~66 % and 25~52 % to the citywide average PM〈sub〉2.5〈/sub〉 concentrations of 45~126 and 14~31 μg m〈sup〉−3〈/sup〉 in the winter and summer, respectively. This study demonstrates the importance of joint emission control efforts among cities within the SCB and neighbor regions to the east.

Description: 〈b〉MAX-DOAS measurements of tropospheric NO〈sub〉2〈/sub〉 and HCHO in Nanjing and the comparison to OMI observations〈/b〉〈br〉 Ka Lok Chan, Zhuoru Wang, Aijun Ding, Klaus-Peter Heue, Yicheng Shen, Jing Wang, Feng Zhang, Nan Hao, and Mark Wenig〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1266,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 The manuscript presents long term observations of atmospheric nitrogen dioxide (NO〈sub〉2〈/sub〉) and formaldehyde (HCHO) in Nanjing using a MAX-DOAS instrument. The measurements were performed from April 2013 to February 2017. The MAX-DOAS measurements of NO〈sub〉2〈/sub〉 and HCHO are used to validate OMI satellite observations and to investigate the influences of region transport of air pollutants on the air quality in Nanjing.

Description: 〈b〉Detection of Outflow of Formaldehyde and Glyoxal from the African continent to the Atlantic Ocean with a MAX-DOAS Instrument〈/b〉〈br〉 Lisa K. Behrens, Andreas Hilboll, Andreas Richter, Enno Peters, Leonardo M. A. Alvarado, Anna B. Kalisz Hedegaard, Folkard Wittrock, John P. Burrows, and Mihalis Vrekoussis〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1286,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 MAX-DOAS measurements were conducted on the research vessel Maria S. Merian during a cruise from the Azores to South Africa in October 2016. The measurements indicate enhanced levels of HCHO and CHOCHO over the remote Atlantic Ocean, which is unexpected due to their short lifetime. Precursors of these gases or gas-aerosol combinations might be transported. Model simulations indicate potential source regions over the African continent, probably related to biomass burning or biogenic emissions.

Description: 〈b〉Develop a coupled agent-based modeling approach for uncertain water management decisions〈/b〉〈br〉 Jin-Young Hyun, Shih-Yu Huang, Y. C. Ethan Yang, Vincent Tidwell, and Jordan Macknick〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-555,2019〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 This study applies a 〈q〉two-way〈/q〉 coupled agent-based model (ABM) with a River-Reservoir management model (RiverWare) to address the interaction between human and natural systems using Bayesian Inference (BI) mapping joined with Cost-Loss (CL). The calibration results show that this methodology can capture the historical pattern of both human activities and natural dynamics and outperforms those without using BI and CL.

Description: 〈b〉Potentials and pitfalls of permafrost active layer monitoring using the HVSR method: a case study in Svalbard〈/b〉〈br〉 Andreas Köhler and Christian Weidle〈br〉 Earth Surf. Dynam., 7, 1-16, https://doi.org/10.5194/esurf-7-1-2019, 2019〈br〉 The uppermost part of permanently frozen ground can thaw during summer and refreeze during winter. We use a method based on naturally generated seismic waves to continuously monitor these changes close to the research settlement of Ny-Ålesund in Svalbard between April and August 2016. Our results reveal some potential pitfalls when interpreting temporal variations in the data. However, we show that a careful data analysis makes this method a very useful tool for long-term permafrost monitoring.

Description: 〈b〉Long-profile evolution of transport-limited gravel-bed rivers〈/b〉〈br〉 Andrew D. Wickert and Taylor F. Schildgen〈br〉 Earth Surf. Dynam., 7, 17-43, https://doi.org/10.5194/esurf-7-17-2019, 2019〈br〉 Rivers can raise or lower their beds by depositing or eroding sediments. We combine equations for flow, channel/valley geometry, and gravel transport to learn how climate and tectonics shape down-valley profiles of river-bed elevation. Rivers steepen when they receive more sediment (relative to water) and become straighter with tectonic uplift. Weathering and breakdown of gravel is needed to produce gradually widening river channels with concave-up profiles that are often observed in the field.

Description: 〈b〉Definition differences and internal variability affect the simulated Arctic sea ice melt season〈/b〉〈br〉 Abigail Smith and Alexandra Jahn〈br〉 The Cryosphere, 13, 1-20, https://doi.org/10.5194/tc-13-1-2019, 2019〈br〉 Here we assessed how natural climate variations and different definitions impact the diagnosed and projected Arctic sea ice melt season length using model simulations. Irrespective of the definition or natural variability, the sea ice melt season is projected to lengthen, potentially by as much as 4–5 months by 2100 under the business as usual scenario. We also find that different definitions have a bigger impact on melt onset, while natural variations have a bigger impact on freeze onset.

Description: 〈b〉Three decades of simulated global terrestrial carbon fluxes from a data assimilation system confronted to different periods of observations〈/b〉〈br〉 Karel Castro-Morales, Gregor Schürmann, Christoph Köstler, Christian Rödenbeck, Martin Heimann, and Sönke Zaehle〈br〉 Biogeosciences Discuss., doi:10.5194/bg-2018-517,2019〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 To obtain nearly thirty years of global terrestrial carbon fluxes, we simultaneously incorporated in a land surface model three different time periods of two observational data sets: absorbed photosynthetic active radiation and atmospheric CO〈sub〉2〈/sub〉 concentrations. One decade of data is enough to improve the modeled long-term trends and seasonal amplitudes of the assimilated variables, particularly in boreal regions. This model has the potential to provide short-term predictions of land carbon fluxes.

Description: 〈b〉Ostracods as ecological and isotopic indicators of lake water salinity changes: The Lake Van example〈/b〉〈br〉 Jeremy McCormack, Finn Viehberg, Derya Akdemir, Adrian Immenhauser, and Ola Kwiecien〈br〉 Biogeosciences Discuss., doi:10.5194/bg-2018-476,2019〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 We juxtapose changes in ostracod taxonomy, morphology (noding) and oxygen (δ〈sup〉18〈/sup〉O) and carbon (δ〈sup〉13〈/sup〉C) isotopic composition for the last 150 kyr with independent low-resolution salinity proxies. We demonstrate that for Lake Van, salinity is the most important factor influencing the composition of the ostracod assemblage and the formation of nodes on the valves of limnocytherinae species. Ostracod δ〈sup〉18〈/sup〉O shows a higher sensibility towards climatic and hydrological variations than the bulk isotopy.

Description: 〈b〉Organic signatures in Pleistocene cherts from Lake Magadi (Kenya), analogs for early Earth hydrothermal deposits〈/b〉〈br〉 Manuel Reinhardt, Walter Goetz, Jan-Peter Duda, Christine Heim, Joachim Reitner, and Volker Thiel〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-513,2019〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 Organic matter in Archean hydrothermal cherts may contain molecular traces of early life. Alteration processes during and after deposition, however, may have obliterated potential biosignatures. Our results from modern analog samples (Pleistocene cherts from Lake Magadi, Kenya) show that biomolecules can survive early hydrothermal destruction in the macromolecular fraction of the organic matter. A conservation of molecular biosignatures in Archean hydrothermal cherts therefore seems possible.

Description: 〈b〉Detection of Outflow of Formaldehyde and Glyoxal from the African continent to the Atlantic Ocean with a MAX-DOAS Instrument〈/b〉〈br〉 Lisa K. Behrens, Andreas Hilboll, Andreas Richter, Enno Peters, Leonardo M. A. Alvarado, Anna B. Kalisz Hedegaard, Folkard Wittrock, John P. Burrows, and Mihalis Vrekoussis〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1286,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 MAX-DOAS measurements were conducted on the research vessel Maria S. Merian during a cruise from the Azores to South Africa in October 2016. The measurements indicate enhanced levels of HCHO and CHOCHO over the remote Atlantic Ocean, which is unexpected due to their short lifetime. Precursors of these gases or gas-aerosol combinations might be transported. Model simulations indicate potential source regions over the African continent, probably related to biomass burning or biogenic emissions.

Description: 〈b〉Primary and secondary sources of ambient formaldehyde in the Yangtze River Delta based on OMPS observation〈/b〉〈br〉 Wenjing Su, Cheng Liu, Qihou Hu, Shaohua Zhao, Youwen Sun, Wei Wang, Yizhi Zhu, Jianguo Liu, and Jhoon Kim〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1192,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 For a better understanding of the pollution and atmospheric chemistry of HCHO, we evaluated its primary and secondary sources in the Yangtze River Delta based on HCHO column density from Ozone Mapping and Profiler Suite (OMPS) and combining with surface in-situ measurements. We found that secondary formation contributed most to ambient HCHO for a long time, but primary emission could be dominant in the winter. The usability of total HCHO as the proxy of VOCs reactivity depends on time scale.

Description: 〈b〉Greenland Ice Sheet late-season melt: Investigating multi-scale drivers of K-transect events〈/b〉〈br〉 Thomas J. Ballinger, Thomas L. Mote, Kyle Mattingly, Angela C. Bliss, Edward Hanna, Dirk van As, Melissa Prieto, Saeideh Gharehchahi, Xavier Fettweis, Brice Noël, Paul C. J. P. Smeets, Mads H. Ribergaard, and John Cappelen〈br〉 The Cryosphere Discuss., https//doi.org/10.5194/tc-2018-285,2019〈br〉 〈b〉Manuscript under review for TC〈/b〉 (discussion: open, 0 comments)〈br〉 Studies have questioned links between Arctic marginal sea open water duration and Greenland Ice Sheet (GrIS) surface balance changes, namely melt events. Through analyses involving observations and climate models, we show that late summer through autumn “unseasonal” melt events are primarily driven by the northward movement of warm, moist air masses across the western ice sheet edge, while near-surface, off-ice winds block heat transfer off nearby Baffin Bay.

Description: 〈b〉Snow cover variability across glaciers in Nordenskiöldland (Svalbard) from point measurements in 2014–2016〈/b〉〈br〉 Marco Möller and Rebecca Möller〈br〉 Earth Syst. Sci. Data Discuss., https//doi.org/10.5194/essd-2018-158,2019〈br〉 〈b〉Manuscript under review for ESSD〈/b〉 (discussion: open, 0 comments)〈br〉 Snow water equivalents (SWE) are useful for calibration and validation of different snow cover-related modeling efforts (e.g. glacier mass balance or snow drift). They form a measure of snow accumulation better than snow depth as they are independent of density differences and thus comparable. A dataset is presented which provides point data of snow depth and density measurements as well as of calculated SWE from 109 locations on glaciers in the central region of the Arctic archipelago Svalbard.

Description: 〈b〉Fifty years of recorded hillslope runoff on seasonally-frozen ground: The Swift Current, Saskatchewan, Canada dataset〈/b〉〈br〉 Anna E. Coles, Jeffrey J. McDonnell, and Brian G. McConkey〈br〉 Earth Syst. Sci. Data Discuss., https//doi.org/10.5194/essd-2018-126,2019〈br〉 〈b〉Manuscript under review for ESSD〈/b〉 (discussion: open, 1 comment)〈br〉 〈p〉Long records of hillslope runoff and nutrients are rare – on seasonally frozen ground they are almost non-existent. The Swift Current hillslopes at the Swift Current Research and Development Centre on the Canadian Prairies provide such a long-term hydrological record. Runoff, runoff nutrient concentration, snowpack, soil moisture, and soil nutrient concentration were monitored on the three 5 ha hillslopes over a 50-year period (1962–2011). Runoff from the hillslopes was generated episodically during snowmelt and occasional rainfall events. Edge-of-field runoff was measured with a 0.61 m H-flume. Daily runoff nutrient concentration data are available for nitrate (March 1971–April 2011), ammonium (February 1996–April 2011), and orthophosphate (March–April 1971; June 1991–April 2011). Snowpack data (snowpack depth, density and water equivalent) were determined via manual snow surveys carried out several times each winter, between January and March, between 1965 and 2011 Gravimetric soil moisture content was measured in October and April each year between 1971 and 2011 at five depth intervals (0–15, 15–30, 30–60, 60–90, and 90–120 cm) at nine points on each hillslope. We summarize these hillslope data in two publically-available repositories: 1) 1962–2011 data on runoff, runoff nutrients, snowpack, soil moisture, soil nutrients, and crop and tillage practices at 〈a href="https://doi.org/10.23684/hhn5-rz52" target="_blank"〉https://doi.org/10.23684/hhn5-rz52〈/a〉; and 2) digital elevation data at 〈a href="https://doi.org/10.20383/101.011" target="_blank"〉https://doi.org/10.20383/101.011〈/a〉. Complete climate data recorded at a Environment and Climate Change Canada meteorological station located 390 m from the three hillslopes are publically-available at 〈a href="http://climate.weather.gc.ca/" target="_blank"〉http://climate.weather.gc.ca/〈/a〉.〈/p〉

Description: 〈b〉GemPy 1.0: open-source stochastic geological modeling and inversion〈/b〉〈br〉 Miguel de la Varga, Alexander Schaaf, and Florian Wellmann〈br〉 Geosci. Model Dev., 12, 1-32, https://doi.org/10.5194/gmd-12-1-2019, 2019〈br〉 〈i〉GemPy〈/i〉 is an open-source Python-based 3-D structural geological modeling software, which allows the implicit (i.e. automatic) creation of complex geological models from interface and orientation data. 〈i〉GemPy〈/i〉 is implemented in the programming language Python, making use of a highly efficient underlying library, Theano, for efficient code generation that performs automatic differentiation. This enables the link to probabilistic machine-learning and Bayesian inference frameworks.

Description: 〈b〉Comparison of the GRUAN data products for Meisei RS-11G and Vaisala RS92-SGP radiosondes at Tateno (36.06° N, 140.13° E), Japan〈/b〉〈br〉 Eriko Kobayashi, Shunsuke Hoshino, Masami Iwabuchi, Takuji Sugidachi, Kensaku Shimizu, and Masatomo Fujiwara〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-416,2019〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The authors carried out dual flights of RS-11G and RS92-SGP radiosondes and investigated the differences in the performance of the radiosondes to help characterize GRUAN data products. A novel aspect of GRUAN data products is that vertically resolved uncertainty estimates and metadata are provided for each sounding and comparison of GRUAN data products is important in securing the temporal homogeneity of climate data records.

Description: 〈b〉WHU-SGCC: A novel approach for blending daily satellite (CHIRP) and precipitation observations over Jinsha River Basin〈/b〉〈br〉 Gaoyun Shen, Nengcheng Chen, Wei Wang, and Zeqiang Chen〈br〉 Earth Syst. Sci. Data Discuss., https//doi.org/10.5194/essd-2018-150,2019〈br〉 〈b〉Manuscript under review for ESSD〈/b〉 (discussion: open, 0 comments)〈br〉 The development of effective methods for high-accuracy precipitation estimates over complex terrain and on a daily scale is important for mountainous hydrological applications. This study offers a novel approach called WHU-SGCC by blending rain gauged and satellite data, to estimate daily precipitation at 0.05° resolution over Jinsha River Basin, the complicated mountainous terrain with sparse rain gauge data, considering the spatial correlation and the historical precipitation characteristics.

Description: 〈b〉GemPy 1.0: open-source stochastic geological modeling and inversion〈/b〉〈br〉 Miguel de la Varga, Alexander Schaaf, and Florian Wellmann〈br〉 Geosci. Model Dev., 12, 1-32, https://doi.org/10.5194/gmd-12-1-2019, 2019〈br〉 〈i〉GemPy〈/i〉 is an open-source Python-based 3-D structural geological modeling software, which allows the implicit (i.e. automatic) creation of complex geological models from interface and orientation data. 〈i〉GemPy〈/i〉 is implemented in the programming language Python, making use of a highly efficient underlying library, Theano, for efficient code generation that performs automatic differentiation. This enables the link to probabilistic machine-learning and Bayesian inference frameworks.

Description: 〈b〉Merits of novel high-resolution estimates and existing long-term estimates of humidity and incident radiation in a complex domain〈/b〉〈br〉 Helene Birkelund Erlandsen, Lena Merete Tallaksen, and Jørn Kristiansen〈br〉 Earth Syst. Sci. Data Discuss., https//doi.org/10.5194/essd-2018-121,2019〈br〉 〈b〉Manuscript under review for ESSD〈/b〉 (discussion: open, 0 comments)〈br〉 Robust estimates of runoff, snow, and evaporation rely on high quality estimates of incoming solar and thermal radiation at the surface, and near surface humidity. Taking advantage of the physical soundness of a numerical weather reanalyisis and the preciseness and spatial resolution of a national gridded temperature data set, new estimates of these variables are presented for Norway. Further, existing data sets and observations are compared, emphasising daily correlation, trends, and gradients.

Description: 〈b〉Fifty years of recorded hillslope runoff on seasonally-frozen ground: The Swift Current, Saskatchewan, Canada dataset〈/b〉〈br〉 Anna E. Coles, Jeffrey J. McDonnell, and Brian G. McConkey〈br〉 Earth Syst. Sci. Data Discuss., https//doi.org/10.5194/essd-2018-126,2019〈br〉 〈b〉Manuscript under review for ESSD〈/b〉 (discussion: open, 1 comment)〈br〉 〈p〉Long records of hillslope runoff and nutrients are rare – on seasonally frozen ground they are almost non-existent. The Swift Current hillslopes at the Swift Current Research and Development Centre on the Canadian Prairies provide such a long-term hydrological record. Runoff, runoff nutrient concentration, snowpack, soil moisture, and soil nutrient concentration were monitored on the three 5 ha hillslopes over a 50-year period (1962–2011). Runoff from the hillslopes was generated episodically during snowmelt and occasional rainfall events. Edge-of-field runoff was measured with a 0.61 m H-flume. Daily runoff nutrient concentration data are available for nitrate (March 1971–April 2011), ammonium (February 1996–April 2011), and orthophosphate (March–April 1971; June 1991–April 2011). Snowpack data (snowpack depth, density and water equivalent) were determined via manual snow surveys carried out several times each winter, between January and March, between 1965 and 2011 Gravimetric soil moisture content was measured in October and April each year between 1971 and 2011 at five depth intervals (0–15, 15–30, 30–60, 60–90, and 90–120 cm) at nine points on each hillslope. We summarize these hillslope data in two publically-available repositories: 1) 1962–2011 data on runoff, runoff nutrients, snowpack, soil moisture, soil nutrients, and crop and tillage practices at 〈a href="https://doi.org/10.23684/hhn5-rz52" target="_blank"〉https://doi.org/10.23684/hhn5-rz52〈/a〉; and 2) digital elevation data at 〈a href="https://doi.org/10.20383/101.011" target="_blank"〉https://doi.org/10.20383/101.011〈/a〉. Complete climate data recorded at a Environment and Climate Change Canada meteorological station located 390 m from the three hillslopes are publically-available at 〈a href="http://climate.weather.gc.ca/" target="_blank"〉http://climate.weather.gc.ca/〈/a〉.〈/p〉

Description: 〈b〉Calibration and analysis of the uncertainty in downscaling global land use and land cover projections from GCAM〈/b〉〈br〉 Min Chen, Chris R. Vernon, Maoyi Huang, Katherine V. Calvin, and Ian P. Kraucunas〈br〉 Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2018-248,2019〈br〉 〈b〉Manuscript under review for GMD〈/b〉 (discussion: open, 0 comments)〈br〉 Demeter is a community spatial downscaling model that disaggregates land use and land cover changes projected by integrated human-Earth system models. However, Demeter has not been intensively calibrated, and we still lack a good knowledge about its sensitivity to key parameters and the parameter uncertainties. This paper aims to solve this problem.

Description: 〈b〉WHU-SGCC: A novel approach for blending daily satellite (CHIRP) and precipitation observations over Jinsha River Basin〈/b〉〈br〉 Gaoyun Shen, Nengcheng Chen, Wei Wang, and Zeqiang Chen〈br〉 Earth Syst. Sci. Data Discuss., https//doi.org/10.5194/essd-2018-150,2019〈br〉 〈b〉Manuscript under review for ESSD〈/b〉 (discussion: open, 0 comments)〈br〉 The development of effective methods for high-accuracy precipitation estimates over complex terrain and on a daily scale is important for mountainous hydrological applications. This study offers a novel approach called WHU-SGCC by blending rain gauged and satellite data, to estimate daily precipitation at 0.05° resolution over Jinsha River Basin, the complicated mountainous terrain with sparse rain gauge data, considering the spatial correlation and the historical precipitation characteristics.

Description: 〈b〉On the fine vertical structure of the low troposphere over the coastal margins of East Antarctica〈/b〉〈br〉 Étienne Vignon, Olivier Traullé, and Alexis Berne〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1197,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 The sea-level rise associated to climate change will depend on how much the Antarctic ice sheet gain – viz precipitation – or loose mass. The precipitation simulation by climate models used for projections depends on the representation of the atmospheric circulation over and around Antarctica. Using daily measurements from balloon soundings at nine stations, this study characterizes the structure of the atmosphere over the Antarctic coast and assess its representation in a climate model.

Description: 〈b〉Insights into the O : C dependent mechanisms controlling the evaporation of α-pinene secondary organic aerosol particles〈/b〉〈br〉 Angela Buchholz, Andrew T. Lambe, Arttu Ylisirniö, Zijun Li, Olli-Pekka Tikkanen, Celia Faiola, Eetu Kari, Liqing Hao, Olli Luoma, Wei Huang, Claudia Mohr, Douglas R. Worsnop, Sergey A. Nizkorodov, Taina Yli-Juuti, Siegfried Schobesberger, and Annele Virtanen〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1305,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 We studied the evaporation of α-pinene secondary organic aerosol particles in clean air to derive their volatility from the observed size changes. We found that the particles became more resilient to evaporation with increased oxidative age, possibly increasing their lifetime in the atmosphere. Also, increased relative humidity increased the particle evaporation. Mass spectrometry measurements of the particles at different stages of evaporation revealed some water-induced composition changes.

Description: 〈b〉Insights into the O : C dependent mechanisms controlling the evaporation of α-pinene secondary organic aerosol particles〈/b〉〈br〉 Angela Buchholz, Andrew T. Lambe, Arttu Ylisirniö, Zijun Li, Olli-Pekka Tikkanen, Celia Faiola, Eetu Kari, Liqing Hao, Olli Luoma, Wei Huang, Claudia Mohr, Douglas R. Worsnop, Sergey A. Nizkorodov, Taina Yli-Juuti, Siegfried Schobesberger, and Annele Virtanen〈br〉 Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2018-1305,2019〈br〉 〈b〉Manuscript under review for ACP〈/b〉 (discussion: open, 0 comments)〈br〉 We studied the evaporation of α-pinene secondary organic aerosol particles in clean air to derive their volatility from the observed size changes. We found that the particles became more resilient to evaporation with increased oxidative age, possibly increasing their lifetime in the atmosphere. Also, increased relative humidity increased the particle evaporation. Mass spectrometry measurements of the particles at different stages of evaporation revealed some water-induced composition changes.

Description: 〈b〉Quantitative precipitation estimation with weather radar using a data- and information-based approach〈/b〉〈br〉 Malte Neuper and Uwe Ehret〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-606,2019〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 In our study we apply a data-driven approach to estimate precipitation quantitatively with the use of weather radar data. The method is based on Information theory concepts. It uses predictive relations expressed by empirical discrete probability distributions directly derived from data rather than the standard deterministic functions.

Description: 〈b〉Develop a coupled agent-based modeling approach for uncertain water management decisions〈/b〉〈br〉 Jin-Young Hyun, Shih-Yu Huang, Y. C. Ethan Yang, Vincent Tidwell, and Jordan Macknick〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-555,2019〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 This study applies a 〈q〉two-way〈/q〉 coupled agent-based model (ABM) with a River-Reservoir management model (RiverWare) to address the interaction between human and natural systems using Bayesian Inference (BI) mapping joined with Cost-Loss (CL). The calibration results show that this methodology can capture the historical pattern of both human activities and natural dynamics and outperforms those without using BI and CL.

Description: 〈b〉Stochastic modeling of flow and conservative transport in three-dimensional discrete fracture networks〈/b〉〈br〉 I-Hsien Lee, Chuen-Fa Ni, Fang-Pang Lin, Chi-Ping Lin, and Chien-Chung Ke〈br〉 Hydrol. Earth Syst. Sci., 23, 19-34, https://doi.org/10.5194/hess-23-19-2019, 2019〈br〉 Few studies focused on the direct solution of the ADE for 3-D DFNs. The study is the first to solve the ADE and focus on assessing the velocity uncertainty in 3-D DFNs. The velocity uncertainty shows a limited range of influence close to the mean diameter of a fracture. The information is useful for engineering designs at sites with fractured rocks. We quantified that the tracer test in wells might lead to the overestimation of mean concentration and induce high uncertainty in fractured media.

Description: 〈b〉Time-variability of the fraction of young water in a small headwater catchment〈/b〉〈br〉 Michael P. Stockinger, Heye R. Bogena, Andreas Lücke, Christine Stumpp, and Harry Vereecken〈br〉 Hydrol. Earth Syst. Sci. Discuss., https//doi.org/10.5194/hess-2018-604,2019〈br〉 〈b〉Manuscript under review for HESS〈/b〉 (discussion: open, 0 comments)〈br〉 Precipitation moves through the soil to become streamwater. The fraction of precipitation that became streamwater after 3 months (Fyw) can be calculated with the stable isotopes of water. Previously this was done for all the isotope data available, e.g., for several years. We used one year of data to calculate Fyw and moved this calculation time window over the time series. Results highlight that Fyw varies in time. Comparison studies of different regions should take this into account.

Description: 〈b〉The significant contribution of HONO to secondary pollutants during a severe winter pollution event in southern China〈/b〉〈br〉 Xiao Fu, Tao Wang, Li Zhang, Qinyi Li, Zhe Wang, Men Xia, Hui Yun, Weihao Wang, Chuan Yu, Dingli Yue, Yan Zhou, Junyun Zheng, and Rui Han〈br〉 Atmos. Chem. Phys., 19, 1-14, https://doi.org/10.5194/acp-19-1-2019, 2019〈br〉 This study has identified the major contributors to the observed high HONO levels during a severe winter pollution episode and highlighted the importance of HONO chemistry in the combined photochemical and haze pollution in a subtropical region. It also highlighted the critical need to include and update HONO sources in regional air quality models in order to predict ozone and other secondary pollutants better during heavy pollution events in southern China and similar regions.

Description: 〈b〉A reconstruction of warm water inflow to Upernavik Isstrøm since AD 1925 and its relation to glacier retreat〈/b〉〈br〉 Flor Vermassen, Nanna Andreasen, David J. Wangner, Nicolas Thibault, Marit-Solveig Seidenkrantz, Rebecca Jackson, Sabine M. Schmidt, Kurt H. Kjær, and Camilla S. Andresen〈br〉 Clim. Past Discuss., https//doi.org/10.5194/cp-2018-174,2019〈br〉 〈b〉Manuscript under review for CP〈/b〉 (discussion: open, 0 comments)〈br〉 This study shows that warming of ocean waters is related to the retreat of Upernavik Isstrøm, a glacier in Northwest Greenland. We show that in the 1930s and after 2000 the waters in the fjord warmed and the glacier retreated. We found this by investigating microfossils from sediments in Upernavik Fjord; different species occur in response to warmer waters.

Description: 〈b〉The CMEMS GlobColour 〈i〉Chlorophyll-a〈/i〉 Product Based on Satellite Observation〈/b〉〈br〉 Philippe Garnesson, Antoine Mangin, Odile Fanton d'Andon, Julien Demaria, and Marine Bretagnon〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-155,2019〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉This work concerns the chlorophyll products based on Satellite Observation and disseminated in the frame of the Copernicus Marine Environmental Monitoring Service (CMEMS).〈/p〉 〈p〉 This work highlights the main advantages provided by the Copernicus Globcolour processor which is used to serve the CMEMS with a long time series from 1997 to present with level 3 & 4 products at Global level (4 km of spatial resolution) and for the Atlantic level 4 product (1 km).〈/p〉 〈p〉 It discusses the different ways to merge data coming from different sensors and it is shown that the GlobColour processor approach provide a better flexibility. At present, it is the only one CMEMS processor able to ingest the OLCI-S3A in the merged product (OLCI-S3A data are ingested in the operational CMEMS products since the April 2018 release).〈/p〉 〈p〉 Behind the merging, the flagging strategy to go from level 2 provided by spatial agencies to the level 3 CMEMS products is also discussed. A better spatial coverage is demonstrated, including the coastal area which is of particular interest for many users involved in the EU Water Framework and Marine Strategy Framework Directive.〈/p〉

Description: 〈b〉Induced seismicity in geologic carbon storage〈/b〉〈br〉 Víctor Vilarrasa, Jesus Carrera, Sebastià Olivella, Jonny Rutqvist, and Lyesse Laloui〈br〉 Solid Earth Discuss., https//doi.org/10.5194/se-2018-129,2019〈br〉 〈b〉Manuscript under review for SE〈/b〉 (discussion: open, 0 comments)〈br〉 To meet the goal of the Paris Agreement to limit temperature increase below 2 ºC, Geologic Carbon Storage (GCS) will be necessary at the gigatone scale. But to successfully deploy GCS, seismicity induced by CO〈sub〉2〈/sub〉 injection should be controlled and maintained below a threshold that does not generate nuisances to the population. We conclude that felt induced seismicity can be minimized provided that a proper site characterization, monitoring and pressure management are performed.

Description: 〈b〉Improved aerosol correction for OMI tropospheric NO〈sub〉2〈/sub〉 retrieval over East Asia: constraint from CALIOP aerosol vertical profile〈/b〉〈br〉 Mengyao Liu, Jintai Lin, K. Folkert Boersma, Gaia Pinardi, Yang Wang, Julien Chimot, Thomas Wagner, Pinhua Xie, Henk Eskes, Michel Van Roozendael, François Hendrick, Pucai Wang, Ting Wang, Yingying Yan, Lulu Chen, and Ruijing Ni〈br〉 Atmos. Meas. Tech., 12, 1-21, https://doi.org/10.5194/amt-12-1-2019, 2019〈br〉 China has become the world’s largest emitter of NO〈sub〉〈i〉x〈/i〉〈/sub〉, which mainly comes from vehicle exhaust, power plants, etc. However, there are no official ground-based measurements before 2013, so satellites have been widely used to monitor and analyze NO〈sub〉〈i〉x〈/i〉〈/sub〉 pollution here. Aerosol is the key factor influencing the accuracy of the satellite NO〈sub〉〈i〉x〈/i〉〈/sub〉 product. Our study provides a more accurate way to account for aerosol's influence compared to current widely used products.