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In recent years climate changes have been observed. Extreme weather events are becomingincreasingly. International organizations related to climate research report that 2016 was thewarmest year in the history of measurements, the second in order was the year 2018and the twenty-warmest years in the history of measurements were the last twentyyears. Drought is the most complicated climatic phenomenon among the hazards related to theweather. Drought monitoring is based on the use of large amounts of data: temperature,precipitation, evaporation, soil moisture data and many others. This monitoring requiresconducting a long-term field measurements. Many different satellite data is commonly used in environmental monitoring e.g.: LIDAR,radar, spectral data, thermal imagery etc. Increased of the spatial resolution up to severalmeters or even centimeters pixel dimension, enable to carry out analyses in the operatingmode even in large areas. Additionally, many of the satellite images are open accessdata. The aim of the presented research is to find the relations between indicatorscharacterizing agricultural drought, which were calculated using traditional and remotesensing methods. These relations will help to answer the question, if it is possible to usespectral data for monitoring agricultural drought. The work contains an analysis ofchanges in the availability of water on grasslands in the context of agricultural droughtmonitoring. Preliminary research carried out on grassland in an area with homogeneous weatherconditions, did not show any strong correlation between spectral indicators and ameteorological and hydrological indicators, in terms of moisture content in the soil-plantenvironment. Therefore, it was decided to extend the research in the spatial and temporalaspect and the number of analysed parameters. The research was conducted on grasslands in lowland areas (< 300 m a.s.l.) in LoverSilesian Voivodship, Poland, the research area was about 15,000 km2. CA 800 grasslandwith a total area about 750 km2 were analysed. Spectral data were obtained forthe period between July 2015 to November 2018 from Sentinel-2 (ESA). Severalspectral indicators based on the amount of chlorophyll, anthocyanins, carotenoids andwater content were calculated. Spectral indicator values were correlated with anaverage temperature, precipitation and evaporation for characteristic periods previousthe given image date. The analyses showed spatial and temporal variability of theagricultural drought in the grassland in lowland areas, described using spectraldata. Keyword: agricultural drought, remote sensing, satellite data, drought monitoring,Sentinel-2 [ABSTRACT FROM AUTHOR]

Mars Science laboratory (MSL) has been operating successfully since early August 2012 with the REMS instrument providing extremely valuable atmospheric observations of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements.The REMS-H relative humidity device is based on polymeric capacitive humidity sensors developed by Vaisala Inc. and it makes use of three (3) humidity sensor heads. The humidity device is mounted on the REMS boom providing ventilation with the ambient atmosphere through a filter protecting the device from airborne dust. The REMS-H humidity instrument has created an unprecedented data record of more than two full Martian years.It has measured the relative humidity and temperature at 1.6 m height for a period of 5 minutes every hour as part of the MSL/REMS instrument package. Mars Science laboratory (MSL) has been operating successfully since early August 2012 with the REMS instrument providing extremely valuable atmospheric observations of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements.The annual in situ water cycle based on three full Martian years at the Gale crater will be discussed. We will utilize the REMS-H instrument's in situ observations accompanied by orbital observations and modeling efforts. We will infer the hourly atmospheric VMR from the REMS-H observations and compare these VMR measurements with predictions of VMR given by our 1D column Martian atmospheric/regolith model to investigate the local water cycle, exchange processes and the local climate in Gale Crater.The strong diurnal variation suggests there are surface-atmosphere exchange processes at Gale Crater during all seasons, which deplete moisture to the ground in the evening and nighttime and release the moisture back to the atmosphere during the daytime. Our modeling results presumably indicate that adsorption processes take place during the nighttime and desorption during the daytime. Other processes, e.g. convective turbulence play a significant role in the daytime in conveying the moisture into the atmosphere. A clear increase in the amount of early morning atmospheric humidity was detected from about sol 1800 onward, when Curiosity started to climb onto Mt. Sharp. The MSL MastCam pictures from this time show exposed bedrock scenery with very sparse and thin layers of wind-blown dust. Our simulations indicate that a plausible explanation for the increase of the atmospheric humidity during early mornings could be the Mt Sharp bedrock material a higher inertia low porosity of an exposed bedrock material. [ABSTRACT FROM AUTHOR]

Understanding the changing Arctic water cycle has new urgency as sea ice, moisturesources, and precipitation patterns are rapidly shifting due to climate change. InJuly 2018, we installed a Picarro Continuous Water Sampler and isotopic analyzerto a second-order stream in Pallas-Yllästunturi National Park, Finland. This newintegrated system enables us to continuously measure the stable isotope geochemistry(δ18O and δ2H) of stream water in-situ with exceptionally high-frequency (10/min)allowing us to reveal patterns and processes previously out of reach with standardcampaign sampling. Coupling these data with standard measurements of streamwater discharge, temperature, DOC and pH, as well as event-based precipitation andcontinuous real-time water vapor isotope measurements places watershed and regionalisotope hydrology into a new realm of understanding. Initial results indicate thatduring the prolonged mid-summer 2018 drought, mean stream water δ18O andδ2H values were -14 ± 1 ‰ and -99 ± 2 ‰ respectively. These values reflectthe fundamental recharge of the basin being mostly driven by snow melt water(typical snow δ18O ∼ -17 ‰). Our baseline drought measurements allow us topartition and quantify hydrologic threshold for enrichment of stream water isotopes asprecipitation was detected in the system later in fall 2018, and further for depletion asisotope values decreased when moving towards winter. Continuous high-frequencymeasurements of stream isotope geochemistry will provide insight into how water ismobilized in the catchment on different seasons and an assessment of how futurechanges in precipitation patterns and seasonality of flow regimes will affect Arcticwatersheds. These data will further allow more accurate hydrograph separation andprovide the basis to investigate changing watershed scale ecohydrological pathwaysthrough seasons, including in-stream biogeochemical and biological processes. [ABSTRACT FROM AUTHOR]

In order to advance our ability to predict the future availability of water resources and the risk of water related disasters under a changing climate, it is necessary to bring together the land surface and hydrological modelling communities. This presentation will describe Hydro-JULES, a new research programme funded by the UK's Natural Environment Research Council. The Hydro-JULES programme will build a three-dimensional, open source, community model of the terrestrial water cycle to support and enable collaborative work across the research and academic communities in hydrology and land-surface science. An advanced terrestrial hydrological model will be generated that couples to the Joint UK Land Environment Simulator (JULES) and related models, including the UK Met Office Unified Model. This new five-year programme, is supported by NERC National Capability funding and will be delivered by the Centre for Ecology and Hydrology (CEH) in partnership with the British Geological Survey (BGS) and National Centre for Atmospheric Science (NCAS). Hydro-JULES aims to address critical research questions in the fields of hydrology, land-atmosphere feedbacks, carbon and nutrient cycles, data science and integration with novel instrumentation and Earth observation technologies; quantify the risks of hydro-climatic extremes (e.g., floods and drought) in a changing environment to support long-range planning and policy decisions; improve hydrological forecasting using new sensors and modelling technology. The Hydro-JULES project covers topics in land-surface science and hydrology including: quantification of hydro-meteorological risks, using high-resolution climate predictions for hydrological applications, calculation the impacts of environmental change on evaporation, transpiration, and soil moisture, modelling flood inundation over large areas, representing anthropogenic interventions in the water cycle, and application of new techniques including Earth observation and data assimilation. The presentation will explore the scientific drivers for integrated land surface and hydrological modelling and outline the main elements of the structure of the work programme. We discuss the development of interfaces between components of the terrestrial water cycle to support integrated modelling of the water cycle and associated Earth system feedbacks, and describe mechanisms for community engagement and collaboration. [ABSTRACT FROM AUTHOR]

Precipitation recycling over the Tibetan Plateau (TP) is essential for regional land-atmosphere interactions and hydrological cycle processes. In this study, the characteristic and mechanism of moisture source variation in recent years (1982-2011) are assessed using the quasi-isentropic backward trajectory method and ERA-Interim dataset. The contribution percent of moisture source inside and outside the TP to the total precipitation in 1982-2011 is 39% and 61% respectively. Local evaporative source over the TP, evaporative source from Arabian Sea and over the southeast TP are the sub-regions that with moisture source increasing contribution. Monthly precipitation change for the TP coherence better with the moisture source change outside the TP than inside. Moisture source change inside the TP is mainly because of the latent heat change in 1998-2011 relative to 1982-1997. [ABSTRACT FROM AUTHOR]

The Pan-Third Pole (PTP), which extending westward from the Tibetan Plateau (TP) to Europe, is the core region of the "The Belt and Road" initiative. The TP has experienced a large-scale accelerated warming over the past few decades, which far exceeds the rate of global warming. This warming trend is considered to be the main cause for the retreat of glaciers and have profound impact on the regional and even global hydrologic cycle. Absorbing aerosols are known to exert a great melting potential on these glaciers through reducing snow and ice albedo and radiative forcing. Therefore, understanding the dominating aerosol types, properties and trends in the PTP region is of great significance for assessing the radiative forcing and climatic effects of this region. In this study, the decadal (2007-2016) active (CALIOP/CALIPSO) and passive (MODIS/Aqua and OMI/Aura) satellite measurements are used to derive the climatology of columnar and vertical distribution, optical properties and changing trends of the dominating aerosols over the PTP region. Results indicate that the PTP region has very distinct climatic features from the west to the east as humid-arid-humid climate characteristics. The Taklimakan Desert (TD) and Iranian Plateau (IP) regions are dominated by dust aerosol, elevated smoke aerosol is the dominating type in Central Europe (CE) and Indo-China (IC) regions, while TP is the cleanest region of the whole PTP. The contribution of dust to total aerosol extinction was 96% and 86% in TD and IP regions respectively, but 54% and 30% of total aerosol extinction in CE and IC regions were contributed by elevated smoke. The mean aerosol extinction coefficient (MAEC) has obvious difference in different regions of the PTP, aerosol layers with the strongest extinction (>0.1 km-1) mainly occur below 4 km. The weakest extinction layers (>0.001 km-1) mainly distribute between 5-7 km and reach approximately 8 km in the TP region, which indicates pronounced vertical transport in this region. The decadal trends of column aerosol optical depth (AOD) over different regions of PTP related to the contributions of different dominating aerosol types. In IC region, significant upward trend (spring) and downward trend (autumn and winter) of AOD are mainly caused by elevated smoke. In CE region, The downward trends of AOD in spring and winter attribute to polluted dust and elevated smoke, respectively. Elevated smoke has significantly increased in summer over the TP region. [ABSTRACT FROM AUTHOR]

The demands for better representations of physical processes in numerical models and therapid evolution of computing power have boosted the development of models that candescribe the terrestrial water cycle in a coupled approach. Such coupled models simulatewater and energy fluxes in the atmosphere, on the land surface, and in the subsurface in aphysically consistent way, albeit with massive computational costs and high uncertainty of allparameters involved. The main objective of our research is the development of a suitable,ensemble-based data-assimilation framework to update model states and/or parameters of acoupled land surface-subsurface model. Towards this end, we first had to addressthe question of how to generate an adequate ensemble. As simulation system, weused the Terrestrial Systems Modeling Platform TerrSysMP, which couples thecommunity land-surface model (CLM) and the subsurface model Parflow. The modeldomain covers a rectangular area of 1×5km2 and has a uniform depth of 50m.Streams are defined along the northern, southern and western boundaries of thedomain. The subsurface material is divided into four main units, and the top soil layersconsist of three different soil types, each with different vegetation. The referencemodel, which we consider our synthetic truth, has a horizontal grid resolution of10m. For the ensemble, we coarsened the grid to a resolution of 40m. We couldafford 128 realizations with the available computing resources, considering thateach member had to undergo a spin-up phase. Grid coarsening led to smoothedtopographical features. Since local grid refinement is not implemented in Parflow, therivers were wider in the coarser model. We divided the ensemble in four groups:Members of the first group considered spatial variability in the saturated hydraulicconductivity, while soil parameters were considered homogeneous within soil units, andplant physiology was identical to that of the reference model. In a second group,soil parameters were treated as spatially variable fields and subsurface parameterswere homogeneous within each rock unit. The third group contained variationsin plant physiology and homogeneous soil and subsurface parameters. The lastgroup was a combination of the others. We conclude that grid coarsening has amajor effect on overland flow, river discharge, and river infiltration/exfiltration andevaporation rates. River interactions with the subsurface could be compensated, tosome extent, by scaling river parameters, but the overestimation of evaporationrates could not be fixed. The suitability of river-related data of coarsened modelsfor data assimilation is still unclear. For each ensemble group, we could definea distinctive response in the simulated states and fluxes, and therefore establishthe relevance of certain groups of parameters for specific processes within andbetween compartments. Finally, the observed ensemble spread of several model statesand fluxes suggests that our ensemble is suitable for a coupled data assimilation. [ABSTRACT FROM AUTHOR]

Interannual variability of Antarctic Intermediate Water (AAIW) in the tropical North Atlantic is investigated using the GECCO\superscript{2} ocean state estimate and Argo data. AAIW salinity variability near the western boundary is shown to be highly correlated with the western boundary current (WBC) transport on interannual timescales. Northward propagating anomalies are associated with the WBC variability that, in turn, is related to the large-scale wind stress curl forcing by means of the Sverdrup balance. AAIW anomalies also propagate westward with the speed of baroclinic Rossby waves, indicating that the westward propagation of baroclinic Rossby waves also plays a role in the variability of AAIW characteristics. Slow eastward spreading of AAIW anomalies is also identified on decadal timescales. Understanding the observed interannual and decadal variability of AAIW salinity is important to properly interpret salinity changes with respect to changes in the hydrological cycle. [ABSTRACT FROM AUTHOR]

AbstractThis study focuses on future moisture flux change projections over the Tibetan Plateau (TP). The downscaling results for the historical period (1980-2005) was evaluated for water cycle aspects precipitation (P), evaporation (E) and P-E against the Global Land Data Assimilation Systems (GLDAS). Whether the mechanisms applying in the historical period continue to the future (2010-2100) is also investigated by WRF and CCSM projections under two scenarios (RCP4.5 and RCP8.5). The mechanism of P-E changes is analyzed by decomposing into dynamic, thermodynamic and transient eddy components. Compared to the coarse-resolution forcing, the downscaling better reproduces the historical spatial patterns and seasonal means of annual average P, E and P-E over the TP. WRF projects a diverse spatial variation of P-E changes with an increase in northern TP and decrease in southern TP in contrast to the averaged increase in CCSM. The dynamic component dominates P-E changes for the historical period in both CCSM and WRF. In the future, however, the thermodynamic component in CCSM contributes dominantly to P-E changes under RCP4.5 and RCP8.5 from the near-term (2010-2039) to the long-term future (2070-2099). Unlike CCSM, WRF inherits the mechanism seen in the historical period: the dynamic component dominates P-E changes. Further, P-E changes in the dynamical downscaling in the future are less sensitive to warming than its coarse-resolution forcing. [ABSTRACT FROM AUTHOR]

The source of moisture is an important part of the hydrological cycle that affects climate system. Potentially, moisture sources are important controls of the isotope composition of precipitation, but their studies in the continental mid- and low-latitudes are still scarce. We identify moisture uptake locations of precipitation over Postojna (Slovenia) for period from 2009 to 2013. By using HYSPLIT trajectory model of NOAA, we did 5-day reconstruction of air mass history for the days with precipitation and determined the moisture uptake locations along back trajectories. Moisture uptake locations were identified along each trajectory using HYSPLIT output data and standard equations for saturation humidity mixing ratio, saturation vapour pressure and specific humidity. Our analysis showed that during studied period around 45% of the precipitation over Postojna originated from Mediterranean and south Atlantic area, with majority of locations originated in the Adriatic Sea. On the other hand, 41% of precipitation originated from moisture recycled over continents, predominantly from Pannonian basin.Multivariable analyses of source regions do not explain any variability of the oxygen isotope composition of precipitation over Postojna. The large proportion of recycled moisture is originated from transpiration rather than evaporation, which produced water vapour with less negative δ18O values. Thus, recycled moisture has and isotope signature undistinctable from the oceanic moisture sources. Climate parameters partly control δ18O values of precipitation, being highly important in paleoclimate studies. In case of Postojna δ18O values of precipitation, surface temperature is the main climate control, whereas amount effect was not recorded, and winter North Atlantic Oscillation (NAO) does not impact the δ18O values of precipitation. We corelated Western Mediterranean Oscillation (WeMO) with oxygen stable isotope composition and found small, but significant correlation. However, multivariate analyses correlation of WeMO and temperature du not explain more variability than temperature alone. Therefore, our interpretation of δ18O values of precipitation in terms of climate is limited to surface temperature, although at least half of the variability observed still depends on unknown controls of the hydrological cycle.Speleothems from Postojna Cave are under investigation and have the potential to record a δ18O signal related to the δ18O values of precipitation. Therefore, these speleothems may be used to reconstruct temperature in the region. [ABSTRACT FROM AUTHOR]

A design of a 3D printed Zero Tension Lysimeter for tracing percolating water and Dissolved Organic Carbon in soil forests in BelgiumCristina Ariza-Carricondo, Marilyn Roland, Bert Gielen, Eric Struyf, Hugues Titeux, Ivan Janssens, Caroline Vincke.Future climate conditions involve increased temporal rainfall variability, with both increased intensity and increased frequency of high rainfall events. These changes lead to an intensification of the hydrological cycle, with higher runoff flows in the wet periods and stronger dry-out of the soils during the longer drought periods. Such alterations in precipitation patterns will cause large changes in the carbon balance of forests. In particular, hydrological conditions are the main driver of Dissolved Organic Carbon (DOC) leaching, both on intra-annual and inter-annual timescales. Longer periods of drought, and occasional strong precipitation events, could cause a more event-driven carbon export from soils through DOC losses. The importance of dissolved and gaseous export under different precipitation regimes remains largely unexplored, partly because of technical constraints to accurately measuring dissolved export fluxes, and partly due to a strong focus on greenhouse gas balances in current research infrastructures. We have designed a leaching water collector also called Zero Tension Lysimeter (ZTL), 3D printed, which has specific characteristics that have been improved thanks to the experiences of previous studies. The ZTL has been designed to collect the percolating water at different depths with the objective to quantitatively trace the movement of DOC in the soil, without the need to model soil water drainage. This ZTL has been installed in two different ways, to study the consequences of the disturbance caused by the installation.As the goal of the research is to study the effects of altered precipitation regimes on DOC leaching, different manipulation experiments will reproduce expected-future climate phenomena, such as strong droughts followed by heavy rain events. Also during and after those experiments water will be collected and analysed for DOC content.Amount of water added, amount of water collected and analysed at different depths, temperature, soil moisture and soil respiration will be measured in every experimental plot. Measurements will be used to reconstruct the water cycle at two Belgian ICOS forest sites: Brasschaat (Pinus sylvestris) and Vielsalm (Fagus sylvatica and Pseudotsuga menziesii), allowing us to couple the DOC results with forest phenology and climate. This will enable us to assess whether a shift is likely to occur in gaseous vs. DOC losses with changing rain regimes. [ABSTRACT FROM AUTHOR]

Evidence for surface and atmosphere coupling is corroborated in both modeling and observation-based field experiments. Recent advances in high-performance computing and development of convection-permitting regional-scale atmospheric models combined with high-resolution hydrologic models has made modeling of surface atmosphere interactions feasible for the scientific community. These models can account for the impacts of the overland flow and subsurface flow components of the hydrologic cycle. One such model is the Weather Research and Forecasting (WRF) regional atmospheric model that can be coupled to the WRF-Hydro hydrologic model.In the present study, both the uncoupled WRF (advanced research WRF; WRF-ARW) and otherwise identical WRF-Hydro model are executed for the 2017 and 2018 summertime North American Monsoon (NAM) seasons in Arizona, a semi-arid environment. In this environment, diurnal convection is impacted by precipitation recycling from the land surface. Understanding of NAM convection is critical to both the research and the operational communities, as extreme weather events can give rise to flash flooding, severe straight-line winds, and blowing dust. The current work assesses the impact of the representation of hydrologic processes at the land surface, in both modeling setups, and how these affect 1) local surface energy budgets during the NAM throughout Arizona and 2) the spectral behavior of diurnally driven NAM convection. Model results suggest that adding surface and subsurface flow from WRF-Hydro increases soil moisture and latent heat near the surface. This increases the amount of instability and moisture available for deep convection in the model simulations, and enhances the growth of convection at the peak of the diurnal cycle. [ABSTRACT FROM AUTHOR]

The studies conducted in the second half of the Sixteenth Century were crucial both for thebirth of the modern hydrological science and for the modern epistemology. Thanks to the newexperiment–based scientific approach, and to quantitative observation, the Sun was about tobe fully recognized as the engine of the hydrological cycle, instead of an endogenous enginewithin the Earth, originally conjectured by Aristotle to explain the water supply of greatrivers. In 1663 Schott published his opus Anatomia physico–hydrostatica fontium acfluminum in which the opinions of ancient and modern authors about the origin ofsprings and rivers are carefully reviewed and discussed. Schott’s opus, which remarksAristotelian conjectures on the endogenous origin of the main rivers, shows the traditionalstructure of an opiniones book, based on the ancient humanistic and dialecticalmethod. In this book, Schott reports about some observations recently made about the capability ofthe water to rise within a soil column, to which Perrault will refer as a starting point to designthe experiments reported in his classical opus De l’origine des fontaines (1674). In it, afterreviewing previous authors’ opinions and stating his own hypotheses, Perrault reports about aset of experiments which he performed to test three main questions related to basicsoil–hydrological problems. Only few pages are devoted to the experiments and they are placed at a turning pointof the book, after which the results are thoroughly discussed in comparison withquantitative observations made by other authors, also involving observations about thecatchment behaviour in a general sense. With this approach he places himself in theperspective of a deeply renewed epistemology: only a decade passed between thepublication of Schott’s opus and Perrault’s one, but their perspective is radicallydifferent. Moreover, at the same time, the questions posed on the hydrological cycle and on the soilhydrology, which are hardly reproducible by means of a controlled laboratory model,severely tested this modern scientific approach at its beginning. Perrault seems to be aware ofsuch difficulties and his choice to move the point of view from the scale of the laboratorymodel, to that of the catchment, makes him a progenitor of the contemporary epistemology ofcomplexity, which is framed both on laboratory analysis and on cases study. Thus even ifPerrault’s conclusions went in the direction of the ancient opinion, his work is not onlyseminal for hydrology, but also it helps to enlighten some intricate features of scientificrevolution. Aiming at contributing to understand the importance of Perrault’s opus, we will discusshis epistemological importance through the lens of the repeatability of the experiments, of theintriguing didactic aspects which, starting from his experiments, may arise for modernunderstanding of hydrology, and of his attitude to face the complexity of the hydrologicalprocesses. [ABSTRACT FROM AUTHOR]

Soil moisture is an important component of the hydrological cycle. The amount of water stored in the unsaturated zone is related to evapotranspiration, infiltration and surface water flow and hence soil moisture is an important variable for estimating groundwater recharge. These estimates are of great value for calibration and validation of hydrological models that serve as tools for groundwater management. Soil moisture is variable in time and space and through scales. In this study, we combine high resolution Sentinel-1 data with coarse resolution SMOS data to downscale satellite retrieved soil moisture to catchment scale. The radiometric SMOS data relates to soil moisture and has a resolution of 40km. The high resolution radar backscatter from Sentinel-1 reflects the spatial heterogeneity of soil moisture. A linear relation between the radiometric retrieved soil moisture and radar backscatter is assumed with parameters that relate to the spatial heterogeneity. These parameters can be estimated using time series. We apply this approach to an area in West Denmark. In the investigation area, three different kinds of vegetation cover are present: forest plantation, heathland and farm land. Ground-based observations of catchment- and point-scale soil moisture derived with the cosmic-ray method and probes are used to validate the downscaled data. [ABSTRACT FROM AUTHOR]

Dynamic Global Vegetation Models (DGVMs), e.g. LPJ-Guess model, have been widely applied to study transient aspects of ecosystem response (e.g. vegetation dynamics and biogeochemistry) to climate change and certain other aspects of global change. However, there are still considerable disagreements between model simulations and observations, especially in tropic region. It has been observed that Amazon rainforest green up during dry seasons while model simulations show plant productivity in Amazon rainforest rapidly decreases during drought. Amazon rainforest is the planet's largest forest and biologically richest ecosystem, and the changes in the biophysical state of the Amazon rainforest have a strong effect on global climate through associated changes in carbon and hydrological cycles. Therefore, it is of significance to study mechanisms that are not correctly treated in models in order to improve the understanding about carbon and hydrological cycle in Amazonia.The Gross Primary Production (GPP), one of ecological term to describe terrestrial carbon balance, provide important information about the environmental under global climate change, as the critical component of the global carbon cycle is the vegetation, mainly due to photosynthesis. Thus GPP is considered for uncertainty analysis and matiodel evaluon. In addition, LPJ-Guess model is used to model GPP. Results show that increasing soil depth, and considering rooting depth and groundwater depth, allow broadleaf evergreen forests in tropical Amazonia to maintain biophysical function through seasonal drought, as a result of better agreement between modeled GPP and observed GPP. [ABSTRACT FROM AUTHOR]

Tree transpiration in humid tropical forests modulates the global water cycle and is a key driver of climate regulation. Yet, our understanding and predictions of how tropical trees regulate water use in response to climate variability remain elusive. With a progressively warming climate, atmospheric evaporative demand (i.e., vapor pressure deficit, VPD) will be increasingly important for plant functioning, becoming the major control of plant water use in the 21st century. Using measurements in 34 tree species at seven sites across a precipitation gradient in the neotropics, we determined how the VPD threshold at which sap flux levels-off at maximum values (VPD-FD) and maximum sap flux (FDmax) vary with precipitation regime (long-term annual precipitation, MAP; seasonal drought intensity, P-DRY) and two functional traits related to foliar and wood economics spectra (leaf mass per area, LMA; wood specific gravity, WSG). We show that, even though VPD-FD and FDmax are highly variable within sites, they follow a negative trend in response to increasing MAP and P-DRY across sites. LMA and WSG exerted little detectable effects on VPD-FD and FDmax, suggesting that these widely-used integrative traits provide limited explanatory power of dynamic plant responses to environmental variation within hyper-diverse tropical forests. This study demonstrates that long-term precipitation and thus, soil moisture, play a critical role in the transpiration response of humid tropical forests to VPD. Moreover, our findings suggest that under predicted higher evaporative demand, trees growing in wetter environments in humid tropical regions may be subjected to reduced water exchange with the atmosphere relative to trees growing in drier climates. [ABSTRACT FROM AUTHOR]

Marine cold air outbreaks (CAOs) are the dominant weather systems injecting moisture into the mid- and high latitude atmosphere - yet their role in the water cycle is not well understood. We present here a numerical process study of an intense, basin-scale CAO in the Nordic Seas. To that end, we perform simulations with the limited area weather prediction model COSMO at resolutions from coarse to convection resolving. Using tagged water tracers transported within a secondary water cycle built into the model, we follow the moisture that evaporates into the CAO air mass from evaporation to precipitation. Based on these simulations we characterize the water cycle associated with the CAO. Specifically, we show that the CAO is associated with a net injection of moisture of about 7% of the hemispheric mid- to high latitude water content. Thus, we analyse the footprint of the CAO in surface evaporation and precipitation, as well as moisture pathways. Most importantly, we show that the CAO is associated with a highly local water cycle where rapid turnover leads to a residence time of water vapour on the order of only one day. These characteristics of the water cycle are in strong contrast to that of other weather systems that are associated with the long-range transport of moisture, such as frontal systems. The close linkage of CAO formation and the storm track as well as the important contribution of CAOs to the mid- to high latitude moisture budget suggest that CAOs may be an important contributor of latent energy to the diabatic intensification of individual storms. The local nature of the water cycle during CAOs and the decoupling of a cyclone's cold sector from the dynamical ascent regions in its warm sector question, however, to what extent this can be effective. As we demonstrate, the tagging approach provides a promising avenue in addressing this specific question and, more generally, in pinpointing the role of CAOs in the energy budget of a storm track. [ABSTRACT FROM AUTHOR]

A varved lake record extending ca 500 years back in time was reconstructed from Arctic Fennoscandian Lake Kevojärvi (69°45'N 27° 00'E). The lake Kevojärvi is a fluvial lake, where the most prominent feature of an annual hydrological cycle is the accumulation of snow during the winter and the rapid release of water on spring during the melting of snow. The sediments of Lake Kevojärvi are of clastic-organic varve type. The clastic lamina consists of silt and sand particles deposited as a consequence of extensive flooding on spring during which the lake level is rising typically for about two meters. Biogenic lamina is formed of the allochthonous and autochthonous organic matter produced during growing season and preserved at the anoxic bottom waters during the winter stratification under the ice cover. The hydrological cycle and synoptic weather conditions are monitored from the research station at the Lake Kevojärvi. The conditions at the water column is monitored continuously using temperature sensors throughout the water column and multiparameter sonde at the near bottom waters since spring 2017. The varve structure was investigated using microfacies analyses while the chemical composition was analyzed with seasonal resolution using micro-X-ray fluorescence. The detailed monitoring on the catchment and at the water column combined with high resolution varve and chemical records provides a great possibility to reconstruct and understand the past variability of local hydroclimatological conditions in detail. 500-year long Lake Kevojärvi varve record reveal changes in local hydroclimate and correspondence of local hydroclimate to large scale atmospheric circulation patterns. [ABSTRACT FROM AUTHOR]

Agricultural vegetation, as managed ecosystem, showed different structural and physiological characteristics form natural vegetation (forest/grassland), i. e. albedo, leaf area index, surface roughness, canopy resistance. Besides, agricultural vegetation showed distinct phenology with natural vegetation. These differences will alter the biogeophysical and the biogeochemical cycles, causing feedbacks to climate. However, spring phenology change along with cropland expansion by occupying forest or grassland are not well documented, and also its subsequent effects. Here, we firstly quantify spring phenology difference between agricultural vegetation and forest/grassland in spatial details of 0.5º×0.5º of China by adopting both in-situ and satellite-observed method. Agricultural vegetation showed significant later spring phenology (SOS, start of growing season) compared with adjacent natural forest/grassland, with more than 30 days in Northeast China Plain and Xinjiang Oasis region. Such a distinct asynchronous growth will lead to considerable differences on carbon uptake (carbon cycle) and ET (water cycle), and with subsequent impacts on local/regional climate. This study calls for notice of the important role of land cover change induced phenology change and its subsequent biogeophysical and biogeochemical effects. Moreover, more accurate spring phenology of agricultural vegetation in Earth System Models instead of grassland is quite needed to reveal the effects of historical and future cropland expansion. [ABSTRACT FROM AUTHOR]

Theory and observations indicate that plant stomatal conductance decreases in response to increase in the atmospheric CO2. This physiological CO2 response causes reduction in the evapotranspiration and modification of the global hydrological cycle, affecting the global radiative fluxes and climate sensitivity. While this biogeophysical mechanism is included into all comprehensive Earth System Models, its radiative forcing has not been isolated from the other biospheric feedbacks. To evaluate the scale of its radiative forcing, we performed two sensitivity experiments with the CMIP6 version of the MPI Earth system model (MPI-ESM1.2-LR). In addition to the standard 4xCO2 simulation, in which both climate and carbon cycle respond to an instantaneous 4-fold increase in CO2, we performed the 4xCO2rad simulation in which biogeochemistry and plants were not affected by elevated CO2. We analyse changes in outgoing radiation and surface temperature using the Gregory et al. (2004) approach for radiative forcing, and compare results with- and without physiological CO2 response. Rescaling to the doubling of the CO2 concentration, stomatal conductance response increases equilibrium climate sensitivity of the model by ca. 10 %, and its radiative feedback is estimated at 0.14 W/m2/K. This suggest that the magnitude of this positive biogeophysical feedback is comparable with the magnitude of biogeochemical (climate-carbon) feedback.Gregory, J. M., and Coauthors, 2004: A new method for diagnosing radiative forcing and climate sensitivity. Geophys. Res. Lett., 31.L03205, doi:10.1029/2003GL018747. [ABSTRACT FROM AUTHOR]

A thorough understanding of the biogeochemical, water, and energy cycles and their interactions is needed to assess the potential implications of global warming on our future climate. Oceanic-atmospheric oscillation patterns have a strong impact on the variability in the water cycle and, hence on vegetation dynamics. However, the relation between ocean-atmospheric oscillations and hydrology is not yet fully understood. To accurately predict the impact of climate change on hydrology and ecosystem response, a better knowledge about these connections is indispensable.The objective of this study is to identify oceanic-atmospheric controls on hydrology and disentangle the impact of individual climate modes. The approach used in this study is called LASSO (least absolute shrinkage and selection operator) regression, which is a data-driven method that uses automatic feature selection and regularization. In our study, we use LASSO to quantify the impact of 17 major ocean-atmospheric oscillations (e.g., El Niño Southern Oscillation, Northern Atlantic Oscillation) on hydrologic variables, such as precipitation. The methodology allows accounting for cross-correlations in the features, i.e. climate oscillation indices, which can therefore be treated as independent variables. For validation of the LASSO models a nested cross-validation and a significance test using the Benjamini-Hochberg procedure is applied. Additionally, every feature incorporates a possible time lag between zero and five months to account for a potential lagged response of hydrology to ocean-atmospheric oscillations. Both experiments to disentangle the overall effect and the seasonal effect are performed. Looking at the Mediterranean region and using precipitation from CRU (Climatic Research Unit) as response variable, up to 40% of the variability can be explained by ocean-atmospheric oscillations in the winter season model, using data only of December, January and February. We show that the Northern Annular Mode, the East Atlantic Oscillation, the East Atlantic Western Russia Pattern and the North Atlantic Oscillation have a significant impact. These results help us to get a better understanding of how the individual climate modes affect different regions of the world and to gain new insights in the interactions between ocean, atmosphere, land, and ultimately the biosphere. [ABSTRACT FROM AUTHOR]

Wetland ecosystems covers only about 2% of the Earth surface and about 6% of land. Despite such small area, this ecosystems plays an important role in the global water cycle, protecting biodiversity and in the global carbon cycle. Therefore wetlands are important ecosystems and numerous efforts for protection them have been taken in global (e.g. Ramsar Convention on Wetlands), continental (e.g. EU Water Framework Directive) and local (e.g. establishing national parks for protection of wetlands) scale. Preservation of the suitable state of wetland depends mainly on adequate soil hydration resulting of water cycle components. The most important component of the water cycle in wetlands is evapotranspiration. Hence, measurements and modelling of the evapotranspiration in this ecosystems is crucial for determination of underlying processes which are important for preservation of the wetlands. The main aim of this study is to compare the performance of two surface energy balance models, SEBS (Surface Energy Balance System) and SEBAL (Surface Energy Balance Algorithm for Land), in the Upper Biebrza Basin (NE Poland), which is a part of one of the biggest wetlands in Europe. Both of the models are based on remotely sensed data (surface temperature, DEM and vegetation properties), and basic meteorological data. In this study Landsat 8 data from vegetation seasons (April – September) 2014-2017 was used. The results from both models were compared with each other and with ground truth data measured using the eddy covariance method. The eddy covariance tower is located in the Upper Biebrza Basin on the fen. The results show that further work on these types of models applied to wetlands ecosystems should be performed. In further investigations ground truth data for validation and improvement of input parameters should be collected. The research was conducted within the scope of research grant NCN2012/05/B/NZ9/03467 "INterception-TRanspiration-EVaporation; interdependencies of hydrological processes in WETland ECOsystems (INTREV-WetEco)" and project "High-resolution modelling and monitoring of Water and Energy Transfers in wetland ecosystems (HiWET") that is funded by BELSPO STEREO III (INTER/STEREOIII/13/03/HiWET; CONTRACT NR SR/00/301) [ABSTRACT FROM AUTHOR]

The Paleocene – Eocene Thermal Maximum (PETM) is marked by approximately 5 °C of global surface and deep ocean warming, superimposed on already warm latest Paleocene climates. The PETM is characterized by a negative stable carbon isotope excursion (CIE) in the global exogenic carbon pool, poleward migration of thermophilic biota, ocean acidification, increased weathering, photic zone euxinia and intensified hydrological cycle. Reconstructed temperatures for the PETM in mid and high-latitudes regularly exceed modern open marine tropical temperatures. However, constraints on absolute tropical temperatures and the biotic response during the PETM were lacking.Recently, 3 new localities from the equatorial Atlantic yielded constraints on sea surface temperature. These records revealed warming of 3-4ºC of already warm sea water (33-34 ºC) to extremely warm sea surface temperatures (~37ºC) during the PETM. This indicates persistent polar amplification and refutes tropical thermostat theory even at extremely high temperatures. Similar to the biotic response at higher latitude localities, early stages of the PETM are marked by acme events of thermophilic dinoflagellate cysts (dinocysts) in these equatorial records. We also record widespread deoxygenation, expressed as photic zone euxinia on the shelf and expanding oxygen minimum zones further offshore. However, in stark contrast to the flourishing plankton communities at mid and high latitudes, we observe a nearly complete absence of planktic eukaryote microfossil groups during peak warmth. Surprisingly, this absence cannot be explained by anoxia, acidification, preservation biases or sediment dilution. Based on multi-proxy evidence, we find the absence is best explained by heat-stress. We re-examined published data in other oceanic basins and argue heat-stress may have been more widespread in tropical oceans than previously considered. We will discuss the latest insights and implications in the context of other transient rapid warming events and subsequent recovery. [ABSTRACT FROM AUTHOR]

Hydrologic models have been proposed to assess the impact of urbanization and climate change on water resources. The Catchment Hydrologic Cycle Assessment Tool (CAT) is a semi-distributed hydrological model based on physical parameters and it has a link-node model structure (Kim and Jang, 2017). The model includes evapotranspiration, infiltration, groundwater movement, and channel routing sub-modules. Particularly, the hydrologic process in paddy fields and other areas can be simulated with improved facilities such as pond, infiltration trench, bio-retention, wetland, and rainwater harvesting. The improved facilities support to evaluate the potential damages caused by human interruption and play a vital rule to establish sustainable environmental gains in Asian catchments. The CAT model has been tested and verified from small to large size catchments in Korea (Birhanu et al., 2018; Jang et al., 2016). In addition, it was applied for a small peri-urban catchment in U.K. (Miller et al., 2014) and paddy irrigation area in Thailand. The model conceptualization and development is based on single layered unconfined aquifers assumptions. The Darcy–Weisbach equation is used to compute the groundwater movement. The rainfall-runoff process depends on the response of pervious, impervious and paddy areas. The infiltration can be simulated using Green-Ampt, Rainfall Excess, and Horton equations. The Kinematic Wave, Muskingum-Cunge and Muskingum methods are implemented for channel routing. The recent model is upgraded to CAT version 3.0, it integrates GIS pre-processor that allows extracting physical parameters and catchment characteristics from DEM, land use and soil map. In addition, it allows estimating potential evapotranspiration other than Penman-Monteith equation using the Blaney-Criddle, Hamon, Turc, Hargreaves methods. The upgraded model was released in May 2018 (watercycle.kict.re.kr) and several conceptual lumped models (GR4J, GSM, HBV, SYMHYD, TANK, TPHM) including PEST parameter optimization is integrated. The integration of multiple model structures with PEST optimization algorithm enables the user to implement a simple model structure for areas with limited data and facilitates the calibration process.Acknowledgments: This research is supported by the Research Program (20190101-001) of Korea Institute of Civil Engineering & Building Technology and by the Korea Environmental Industry & Technology Institute (KEITI) grant funded by the Ministry of Environment (Grant 18AWMP-B083066-05). ReferencesBirhanu, D., Kim, H., Jang, C. and Park, S.: Does the Complexity of Evapotranspiration and Hydrological Models Enhance Robustness?, Sustainability, 10(8), 2837, 2018.Jang, C. H., Kim, H. J., Ahn, S. R. and Kim, S. J.: Assessment of hydrological changes in a river basin as affected by climate change and water management practices, by using the cat model, Irrig. and Drain., 65, 26–35, 2016.Kim, H. and Jang, C. H.: Catchment Hydrologic Cycle Assessment Tool - A User Guide, Korea Institute of Civil Engineering and Building Technology, Korea, 2017.Miller, J. D., Kim, H., Kjeldsen, T. R., Packman, J., Grebby, S. and Dearden, R.: Assessing the impact of urbanization on storm runoff in a peri-urban catchment using historical change in impervious cover, J. Hydrol., 515, 59–70, 2014. [ABSTRACT FROM AUTHOR]

Under the framework of the EU-Horizon 2020 project BINGO (Bringing INnovation to onGOing water management), climate change impacts on the water cycle in the Wupper catchment area are being studied. For this purpose, the Soil and Water Assessment Tool (SWAT) has been set up, calibrated and validated. The model integrates detailed spatially and temporarily distributed soil, land-surface and meteorological information and can therefore closely link the impact of changes in climate variables to future changes in the numerous hydrological system variables. In this study, short-term (decadal) as well as long-term (centennial) impacts of climate change scenarios are examined, for the Wupper sub-catchment "Große Dhünn". This sub-catchment generates the inflow to a large reservoir, which is used as drinking water source for about 0.5 million people and as flood protection system for downstream areas. Changes of principal water balance components due to climate change, are therefore of high importance in this region.Climate change information are derived from medium-term decadal predictions, based on the MiKlip framework, for the time span 2015-2024, as well as from long-term IPCC-RCP scenarios, for the years 2006-2100. The study assesses potential future hydrological changes in the "Große Dhünn" catchment, based on both data sets and compares the projected changes for the overlapping time period (2015-2024).Decadal predictions as well as IPCC-RCP scenarios indicate that in the near future, winter months will experience reduced reservoir inflow, while summer inflow will slightly increase. The main reason for the decreasing winter discharge rates lays in decreasing precipitation during the respective winter months. In addition, temperature and concurrently also ET rates will increase during winter, which will intensify the decrease in discharge rates. Increasing summer temperatures and ET rates are compensated by increasing summer precipitation rates, and are resulting in a slight increase in summer discharge rates.For long-term predictions however, RCP scenarios indicate that under both RCP scenarios a significant reduction of inflow to the reservoir is expected in all seasons. Furthermore low flows will shift from early to late summer, making a careful management and saving of water resources until later in the hydrological year necessary.A comparison of simulated runoff based on decadal predictions and IPCC-RCP runoff scenarios reveals the interesting fact, that decadal predictions might underestimate the variability of future runoff responses to climate change. While RCP scenarios show a similar variability in runoff compared to historical data, decadal predictions indicate a significant reduction in future runoff variability. This is especially important to consider for future reservoir management, considering the range of potential extreme high and low flows in the near-future. [ABSTRACT FROM AUTHOR]

Recent global studies suggest that the total emission of CO2 from streams and rivers is highly significant and correspond to as much as 85% of the total oceanic CO2 uptake. To address this issue, a large boreal river in Northern Sweden (Indalsälven) was instrumented in April 2018 with water-side measurements combined with an atmospheric eddy-covariance system measuring the vertical fluxes of CO2. This is one of the first known studies of its kind where long term eddy covariance measurements are conducted in a river settingThe river Indalsälven was found to be almost constantly oversaturated with respect to CO2 and with high water-side pCO2 dynamics varying in the range of 400-4500 ppm. During the spring, the pCO2 in the water was in the range of 500-700 ppm and at the same time, large emissions of CO2 from the river were measured. The rapid snowmelt resulting in high water flow in combination with occasionally high winds resulted in high gas transfer velocities, k600. By the beginning of July, the pCO2 in water had increased to over 4000 ppm, likely due to high aquatic degradation of organic material. During the period of July to September, a diel cycle of pCO2 in water was observed with amplitudes of up to several thousand ppm. Simultaneously CO2 emissions in the range of 13-17 µmol m-2s-1 were measured. Wind speed showed a positive correlation with the measured CO2 emissions and k600, with the highest emissions associated to data from the wind sector where the upwind distance to land was greatest.Our data show that a boreal river act as a strong source of atmospheric CO2. The dynamic behaviour in pCO2 and emission clearly highlight the importance of continuous high-frequency CO2 measurements in order to correctly incorporate rivers in landscape carbon balances. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) or the water vapour flux is an important component in the water cycle and is widely studied due to its implications in disciplines ranging from hydrology to agricultural and climate sciences. In the recent past, growing attention has been given to estimating ET fluxes at regional and global scales. However, estimation of ET at large scales has been a difficult task due to direct measurement of ET being possible only at point locations, for example using flux towers. For the African continent, only a limited number of flux tower data are openly available for use, which makes verification of regional and global ET products very difficult. Recent advances in satellite based products provide promising data to fill these observational gaps. ET cannot be directly measured by satellite based measurements, but can be derived from physical variables that can be observed from space, such as latent heat and surface heat using the surface energy balance. In addition, due to passing frequencies and cloud interference, interpolations in time are required. In this respect, remote sensing derived ET cannot be interpreted as direct satellite observations but as model outputs generated based on satellite forcing data. Satellite observations often give useful information on the spatial variability, however the products tend to suffer from a large bias. Since it is difficult to validate ET estimates using observed data points, a method of inferring ET for a basin based on observed data is to subtract discharge (Q) from precipitation (P). Using this general water balance, it is possible to gain an understanding of the magnitude of ET within a given basin from observations of discharge and precipitation data and hence to estimate biases in ET estimation obtained through satellite images. However, there is little overlap between measured discharge and RS derived estimations of ET which poses the problem of finding overlapping time periods for comparison. Therefore, can we justify evaluating estimations of ET using different time periods? A trend analysis can be done in order to justify the use of possible different time periods. Spatial variability can be analysed using specific land cover elements that tend to have a higher or lower ET such as lakes, forested and irrigated areas deltas and deserts. This study focuses on a methodology for evaluating ET products (GLEAM, WAPOR, MODIS, ETMONITOR, SSEBop, WECANN) from observations and observation based ET estimates at the continental scale over Africa using long-term averages of ET for available time periods. The spatial variability is evaluated by comparing different land cover classes with known higher or lower values of ET. Results indicate that most remote sensing products are strongly biased when compared to P-Q estimations at catchment scale. From the data analysed, the recently published WAPOR data set is outperforming other existing remote sensing products. Providing unbiased daily ET products with a resolution of 30-250 meters, the WAPOR dataset shows to be a promising dataset that can be used as a reference for inter-model comparisons. [ABSTRACT FROM AUTHOR]

Increasing CO2 concentrations and future climate change will affect the ability of ecosystemsto sequester carbon due to increasing nutrient limitation, in particular nitrogen (N), which isthe key limiting nutrient in many terrestrial ecosystems. However, the N deficit is difficult, ifnot impossible, to quantify simply from the ecosystem monitoring data. One of the mostcommon tools used is the N stable isotope composition, either at natural abundance, wherethe isotopic fractionation of different processes can indicate N limitation, or asadded tracer in manipulative experiments to trace the fate of N in the ecosystem.Despite the wealth of data, terrestrial biosphere models do not often include thecapacity to include 15N in their predictions, making it difficult to use the availableinformation. We have developed a new terrestrial biosphere model QUINCY (QUantifying Interactionsbetween terrestrial Nutrient CYcles and the climate system) which includes fully coupledcarbon, nutrient and water cycles, as well as an improved representation of plant and soilphysiological processes. Most importantly, we include a 15N tracer to all soil and vegetationpools that allows us to evaluate our model against observations directly. Here, wepresent the first results from a land surface model which includes explicit isotopetracers. First, we explore the trends in foliar 15N during the last century at over 400 forest sitesworldwide. The observed trends of foliar 15N show a decline during the last decades implyingincreasing N deficiency in the ecosystems but attributing the driver of these changes is notstraightforward simply from observations. Our model is able to replicate the observed trendand we show that it is caused by the CO2 fertilisation effect, rather than changes in climateand N deposition. Next, we test the model at two manipulative experimental sites, the Free-Air Carbondioxide Enrichment (FACE) experiment at Oak Ridge National Laboratory (ORNL),where measurements of natural abundance 15N allow an in-depth exploration ofN limitation under elevated CO2, and the 15N enrichment experiment at Cornell,where the 15N tracer allows us to explore fate of added N in soil and vegetationpools. These three case studies showcase the utility of a terrestrial biosphere model withintegrated isotope tracers to not only predict the observed state of the ecosystem but alsoexplore the fundamental drivers and internal ecosystem processes. [ABSTRACT FROM AUTHOR]

Snow cover in the Qinghai-Tibet Plateau (QTP) is a critical component in the water cycle and regional climate of East Asia. Satellite data from three different sources (i.e., the Multi-Sensor Synergy of FengYun-3 (FY3A/B/C MULSS), the Moderate Resolution Imaging Spectroradiometer (MODIS), and the Interactive Multi-sensor Snow and Ice Mapping System (IMS)) were used to analyze the QTP fractional-snow-cover (FSC) change and associated uncertainties in the last decade. A four-step cloud removal procedure was applied to those data, which effectively reduced the cloud percentage from 40.8–56.1% to 2.2–3.3%, with an averaged error about 2% estimated by a random sampling method. Compared with in-situ observations, the cloud-removed FY3B and MODIS have annual mean classification accuracy of about 94%, which is higher than other FY3 data and IMS. Five data sets (FY3A/B/C, MODIS, IMS) show significant differences in snow cover fraction, extent, variation trends and duration changes. IMS has the widest snow cover extent with highest FSC (4.7% and 9.5% higher than MODIS and FY3B FSC, respectively). FY3A/C and MODIS, on morning overpass satellites, have around 5% higher FSC than afternoon-overpass FY3B. The annual FSC and snow duration decrease for 2012–2017 shown by at least two of the FY3B, MODIS and IMS data, but they increase for IMS and decreases for MODIS in recent decade (2006-2017) due to different changing rates of snow onset and melting. Meanwhile, their variation rates increase with the increasing elevation bands lower than 6 km. For uncertainties, higher elevation bands (<6 km) have higher uncertainties, and snow-melting trend has higher uncertainty than snow-onset trend. [ABSTRACT FROM AUTHOR]

High quality climate data at a high spatial and temporal resolution are essential to develop and provide adequate climate services for Africa. Rainfall characteristics such as the number of dry and wet days, extreme rainfall or the length of rainy seasons are derived from regional climate data to create climate service products, e.g. for the agricultural sector. A common method to produce regional climate data is to dynamically downscale global climate change simulations by means of regional climate models (RCMs). These RCMs have to be able to simulate realistically the hydrological cycle in the different African climate zones including the movement of the intertropical convergence zone (ITCZ) over the continent. Deficiencies in the representation of the sea surface temperatures (SSTs) in global ocean models due to a too coarse spatial resolution and missing atmosphere-ocean interactions in RCMs contribute to the rainfall bias over regions affected by the moisture transport from the ocean. The application of a regionally coupled atmosphere-ocean model may reduce the rainfall biases over the African continent.In our work, we analyze the potential impact of the atmosphere-ocean coupling on the simulation of rainfall characteristics over Africa and identify those regions providing an added value using the regionally coupled atmosphere-ocean model ROM. For this purpose, we downscaled the ERA-Interim dataset and the MPI-ESM-LR historical simulation for present climate and the MPI-ESM-LR RCP8.5 simulation for future climate with ROM. Each simulation was downscaled for a time slice of at least 30 years at a spatial resolution of 25 x 25 km² for the whole African continent and the West Atlantic Ocean. In detail, we will show the potential impact of the atmosphere-ocean coupling on droughts and extreme rainfall using different rainfall indices such as consecutive dry days (CDDs), consecutive wet days (CWDs) and very wet days (R95p). Moreover, the effect of the atmosphere-ocean coupling on rainy season parameters will also be analyzed. Finally, a comparison between the bandwidths of the rainfall parameters derived from the uncoupled/coupled projections and the bandwidths of the parameters from the uncoupled CORDEX-CORE Africa ensemble will be shown. [ABSTRACT FROM AUTHOR]

Sub-grid orographic drag directly acts on wind and impacts the regional water cycle through control of atmospheric water vapor (AWV) transport. The effect of turbulent orographic form drag (TOFD) on wind and precipitation is investigated in this study using the WRF model for a winter month over the western Tibetan Plateau (TP), where solid precipitation supplies large amounts of water resources. The diurnal cycle of wind components and atmospheric circulation simulated with TOFD are consistent with observations and ERA-Interim data, whereas stronger westerlies exist in the simulation without the TOFD scheme. The latter results in more zonal AWV transport from the west and more precipitation over the western TP and surroundings. The implementation of the TOFD scheme leads to reduced biases, when evaluated with two observation-based precipitation products. It is therefore concluded that this scheme has a clear dynamical control on the regional atmospheric water recharge and thus the parameterization of the small-scale orographic drag in the model helps to improve the prediction of wintertime precipitation in the western TP region. [ABSTRACT FROM AUTHOR]

Regional climate models (RCMs) are indispensable tools in climate research, e.g., as a basis for process studies and impact assessments of global change. In this study, we inspect regional atmospheric moisture budgets and the atmospheric moisture exchange between the ocean and continental areas from ten representative evaluation experiment RCM ensemble members over Europe at 0.44 degree resolution from 1989 to 2008 taken from the EURO-CORDEX project, driven by ERA-Interim reanalysis, which also constitutes the reference, REF, in the analysis. Over large enough time scales, when atmospheric storage changes are negligible, the atmospheric moisture flux divergence div(q) equals the difference of evapotranspiration (E) from the oceans and land surfaces into the atmosphere, and precipitation (P), div(q)=E-P. Because the RCMs, as limited area models, constitute numerically boundary value problems, all RCMs in the dynamical downscaling setup of the CORDEX evaluation runs use the same lateral boundary conditions and over the oceans the same prescribed reanalysis sea surface temperatures (SSTs). When comparing the E and P of the RCMs for the complete domain, i.e. considering the overall atmospheric moisture budget, the RCMs cluster around the REF values. As expected E exceeds P over the oceans and P exceeds E over land, with a much larger inter-RCM spread over the oceans and a tendency of the RCMs over land and ocean towards a more intense hydrological cycle with higher E and P than REF. Considering differences of E-P over the oceans versus E-P over land, the RCMs are expected to match REF if they reproduce the re-analysis, i.e. the same E over the ocean would be recycled as P over land. Observed deviations from the 1:1 relationship reflect, e.g., effects induced by different boundary forcing treatments in the models. In addition we observe a systematic shift of some RCMs towards higher E-P values over the ocean, leading to higher P over land. We interpret this behaviour as an E-bias of the RCMs over the ocean, associated with the prescribed ERA-Interim SST and flux calculation over the oceans, which may lead to excess P, or rather positively biased P, over land in maintaining div(q) over the model domain prescribed by the boundary conditions. We argue that irrespective of the RCMs' convection and microphysics schemes, the E-flux over the ocean substantially impacts the RCMs P-bias over land. This should be taken into account the setup of modelling studies and the ensuing analyses. [ABSTRACT FROM AUTHOR]

The Indian Summer monsoon is a complex, nonlinear phenomenon involving atmospheric, oceanic, and land-based interactions. Air-sea interactions in the northern Indian Ocean play an important role in regulating the rainfall development of the monsoon. High sea surface temperatures, barrier layer formation due to the development of a freshwater pool, and the associated proclivity to increased convection determine the moisture flux and ultimately rainfall intensity over much of southern Asia. As prediction of rainfall directly determines water management for agriculture, industry, and daily life in countries of this region that rely on monsoon rainfall, it is critical to better understand related dynamical processes for accurate rainfall prediction that impacts over a billion people and is thus important with respect to economic stability and national security. Present understanding of the dynamics pertinent to monsoonal rainfall and its prediction is insufficient. Due to new advances in sea surface salinity satellite technology, the ability to study air-sea interactions between salinity and the hydrologic cycle has never been better. This research provides an opportunity to pioneer an investigation of the role of salinity on monsoonal convection. Because salinity does not directly affect air-sea fluxes, salinity is often neglected in climate-related studies, though recent work has shown that regional salinity can indirectly play an integral role in ocean-atmosphere interactions in the South Eastern Arabian Sea (SEAS) region and monsoon onset. The scientific value of salinity data collected by the recently launched ESA's Soil Moisture Ocean Salinity (SMOS), NASA's Soil Moisture Active Passive (SMAP) and Aquarius (ended in 2015) missions will revolutionize both oceanographic and climate-related studies. It is important to use these new salinity products to validate the forecasting models and understand the different processes in the coupled models. Assimilation of satellite derived salinity in coupled models will also improve the monsoon forecasting. This research also applies the state-of-the-art NOAA/NCEP coupled atmosphere-ocean-land surface-sea ice system, Climate Forecast System (CFSv2.0), in coordination with the HYbrid Ocean Coordinate Model (HYCOM). [ABSTRACT FROM AUTHOR]