Water Budget Analysis Research Articles

Improved Spatiotemporal Representativeness and Bias Reduction of Satellite‐Based Evapotranspiration Retrievals via Use of In Situ Meteorology and Constrained Canopy Surface Resistance

AbstractEvapotranspiration (ET) is a key component of the atmospheric and terrestrial water and energy budgets. Satellite‐based vegetation index approaches have used remotely sensed vegetation and reanalysis meteorological properties with surface energy balance models to estimate global ET (MOD16 ET). We reconstructed satellite retrievals using in situ meteorology (Argonne‐ET) and evaluated them using a dense network of surface turbulent heat flux measurements. Argonne‐ET resolves spatial heterogeneity of ET across the U.S. Southern Great Plains that is not well characterized by MOD16; MOD16 ET exhibits spatial autocorrelation (Moran's I significantly >0 in May–Aug.), whereas in situ and Argonne‐ET exhibit characteristics of a random spatial process (Moran's I not significantly different from 0). The skill in resolving ET temporal variability is not significantly different between MOD16 and Argonne‐ET (correlation coefficient = 0.75 and 0.72, respectively). However, the root‐mean‐square errors were significantly lower for Argonne‐ET (36 W/m2) than MOD16 (43 W/m2), and MOD16 exhibits substantial bias in annual ET relative to in situ measurements (−38%). This is attributed to overestimation in the dry canopy surface resistance (rs) parameterization. Using rs constrained to the range of typical measured values, Argonne‐ET substantially reduces the bias in the annual ET (+1%). The improved ET estimates are critical for regional water budget analyses. The methodology presented herein also demonstrates the ability to retrieve high temporally resolved (30 min; cf. 8‐day MOD16) ET that can be used for development of processed‐based diagnostics of model biases and to elucidate avenues to improve ET model parameterizations.

Role of Lateral Terrestrial Water Flow on the Regional Water Cycle in a Complex Terrain Region: Investigation With a Fully Coupled Model System

AbstractRecent developments in hydrometeorological modeling aim toward a more sophisticated treatment of terrestrial hydrologic processes. The objective of this study is to investigate the role of lateral terrestrial water flows on the regional atmospheric and terrestrial water cycle in a humid region of Central Europe. This is accomplished by evaluating model results from both the standard Weather Research and Forecasting (WRF) model and the hydrologically enhanced version WRF‐Hydro, which allows for a more comprehensive process description of the interdependencies between water and energy fluxes at the land‐atmosphere interface. To account for internal model variability, an ensemble for each model variant is generated for a 3‐month study period in the summer of 2005. The regional water cycle in the simulation domain is investigated by evaluating the ensemble results with a joint atmospheric‐terrestrial water budget analysis. We focus on six differently sized river catchments located in Southern Bavaria (Germany) and the southerly adjacent Eastern Alps, where simulation results are compared to observations of precipitation, near‐surface temperatures, and streamflow. Most prominently, WRF‐Hydro increases (near‐) surface runoff and decreases percolation, resulting in a reduced total runoff amount. Accordingly, soil moisture storage and evapotranspiration are increased. Domain‐averaged precipitation differences between WRF and WRF‐Hydro are essentially related to differences in atmospheric moisture inflow and outflow, which is the signature of internal model variability and is potentially enhanced in the WRF‐Hydro ensemble. Driven only at the boundaries of the outermost domain, the fully coupled model system shows good performance in the reproduction of observed streamflow.

Estimating long-term groundwater storage and its controlling factors in Alberta, Canada

Abstract. Groundwater is one of the most important natural resources for economic development and environmental sustainability. In this study, we estimated groundwater storage in 11 major river basins across Alberta, Canada, using a combination of remote sensing (Gravity Recovery and Climate Experiment, GRACE), in situ surface water data, and land surface modeling estimates (GWSAsat). We applied separate calculations for unconfined and confined aquifers, for the first time, to represent their hydrogeological differences. Storage coefficients for the individual wells were incorporated to compute the monthly in situ groundwater storage (GWSAobs). The GWSAsat values from the two satellite-based products were compared with GWSAobs estimates. The estimates of GWSAsat were in good agreement with the GWSAobs in terms of pattern and magnitude (e.g., RMSE ranged from 2 to 14 cm). While comparing GWSAsat with GWSAobs, most of the statistical analyses provide mixed responses; however the Hodrick–Prescott trend analysis clearly showed a better performance of the GRACE-mascon estimate. The results showed trends of GWSAobs depletion in 5 of the 11 basins. Our results indicate that precipitation played an important role in influencing the GWSAobs variation in 4 of the 11 basins studied. A combination of rainfall and snowmelt positively influences the GWSAobs in six basins. Water budget analysis showed an availability of comparatively lower terrestrial water in 9 of the 11 basins in the study period. Historical groundwater recharge estimates indicate a reduction of groundwater recharge in eight basins during 1960–2009. The output of this study could be used to develop sustainable water withdrawal strategies in Alberta, Canada.

Remote detection of human-induced evapotranspiration in a regional system experiencing increased anthropogenic demands and extreme climatic variability

ABSTRACTParameterizing human-induced evapotranspiration (ET) process in models (e.g. hydrological or land surface models (LSMs)) has been a long-term challenge. As most LSMs can only simulate ET variations under natural climatic conditions, the considerable inconsistency of ET estimations from different approaches can be expected to isolate anthropogenic effects on ET over the developed river basins to some extent, with the premise that uncertainties of multi-ET estimations are well addressed. In this study, monthly ET estimations (2003–2015) from a water budget analysis using Gravity Recovery and Climate Experiment (GRACE) satellites terrestrial water storage solutions (GRACE-ET) and LSMs (model simulated ET (hereafter MOD-ET)) were used to quantify human-induced ET in the Songhua River Basin (SRB). Results indicated that human activities, especially land use changes and water resource management through reservoir regulation posed obvious impact on the reduction of ET from April to October over the SRB. Furthermore, comparison of the estimated annual mean GRACE-ET (441.10 ± 2.03 mm year−1) with MOD-ET (501.31 ± 0.20 mm year−1), indicated that about 12% decrease of ET over the SRB can be attributed to human activities. This study emphasized the unique potential of GRACE satellites for isolating and quantifying human impacts on components of water circulations.

Groundwater flow modelling of a micro-watershed in the upland area of East Godavari district, Andhra Pradesh, India

In view of the progressive decline of groundwater levels in the majority of non-command upland area in the East Godavari district, Andhra Pradesh state, India, there is an urgency to augment groundwater in the non-command upland areas. Groundwater flow model is constructed for a micro-watershed of 50 km2 namely ‘Konda Kalava watershed’ of ‘Suddegedda river basin’ located in the non-command upland area of East Godavari district. The steady state groundwater flow model simulated to seven observation wells and calibrated for the month of April, 2018. The objective of the model is to assess input and output stresses and to identify the over-stressed areas within the basin. The water budget analysis has revealed that the total groundwater extraction by pumping wells is 83.3% and evapotranspiration loss is 5.7% of the total groundwater recharge in the basin. The groundwater flow following the topography and is towards the mainstream with a maximum velocity of 0.4 m/day. The results revealed that the southern part of the basin is experiencing huge aquifer stress due to over-dependence on deep bore wells. It is recommended that, for at least one season, the most affected dry areas which are under paddy cultivation are to be promoted irrigated dry crops such as maize and jowar. It is also suggested that, due to local high salinity in and around Vannepudi village at the central part of the basin, the horticulture cultivation is to be promoted by increasing the surface water resources. The artificial recharge structures have to be constructed at suitable areas in and around Vannepudi village in order to improve the groundwater quality in terms of high salinity and also to rise the groundwater table in the southern part of the basin.

Estimating Basin-Scale Water Budgets with SMAP Soil Moisture Data.

Soil Moisture Active Passive (SMAP) Level-2 soil moisture retrievals collected during 2015-2017 are used in isolation to estimate 10-day warm-season precipitation and streamflow totals within 145 medium-sized (2,000-10,000 km2) unregulated watersheds in the conterminous United States. The precipitation estimation algorithm, derived from a well documented approach, includes a locally-calibrated loss function component that significantly improves its performance. For the basin-scale water budget analysis, the precipitation and streamflow algorithms are calibrated with two years of SMAP retrievals in conjunction with observed precipitation and streamflow data and are then applied to SMAP retrievals alone during a third year. While estimation accuracy (as measured by the square of the correlation coefficient, r2, between estimates and observations) varies by basin, the average r2 for the basins is 0.53 for precipitation and 0.22 for streamflow. For the subset of 22 basins that calibrate particularly well, the r2 increases to 0.63 for precipitation and to 0.51 for streamflow. The magnitudes of the estimated variables are also accurate, with sample pairs generally clustered about the 1:1 line. The chief limitation to the estimation involves large biases induced during periods of high rainfall; the accuracy of the estimates (in terms of r2 and RMSE) increases significantly when periods of higher rainfall are not considered. The potential for transferability is also demonstrated by calibrating the streamflow estimation equation in one basin and then applying the equation in another. Overall, the study demonstrates that SMAP retrievals contain, all by themselves, information that can be used to estimate large-scale water budgets.

Geophysical Measurements to Determine the Hydrologic Partitioning of Snowmelt on a Snow‐Dominated Subalpine Hillslope

AbstractIn subalpine watersheds of the intermountain western United States, snowpack melt is the dominant water input to the hydrologic system. The primary focus of this work is to understand the partitioning of water from the snowpack during the snowmelt period and through the remainder of the growing season. We conducted a time‐lapse electrical resistivity tomography (ERT) study in conjunction with a water budget analysis to track water from the snow‐on through snow‐off season (May–August 2015). Seismic velocities provided an estimate of regolith thickness while transpiration measurements from sap flow in conifer trees provided insight into root water uptake. We observed four hydrologic process‐periods and found that deep flow and tree water fluxes are the primary pathways through which water moves off of the hillslope. Overland flow and interflow were negligible. We observed temporal changes in vadose zone water content more than 3.0 m below the surface. Our results show that vertical flow through the thin soil mantle overlaying coarse colluvial regolith was the primary pathway to a local unconfined aquifer.

A modified FAO evapotranspiration model for refined water budget analysis for Green Roof systems

Many metropolitan cities around the world are promoting the implementation of Green Roofs (GR) as effective stormwater management systems to mitigate adverse effects of urbanization. Hourly water balance calculations are necessary for accurate prediction of the antecedent soil moisture conditions of a GR, a key parameter for rainfall-runoff modeling. However, existing evapotranspiration (ET) models have substantial errors for hourly ET predictions over a range of moisture conditions to accurately assess the hydrological performance of the GRs during storm events. Therefore, a modified Penman-Monteith equation was developed to provide improved prediction of hourly ET specifically for GR applications. ET rates predicted by the modified and established Penmen-Monteith equations were compared with ET data collected from a GR lysimeter over the summer and fall of 2016. The proposed modified Penman-Montieth equation eliminates the water availability factor (θiθfc) included in the equation’s advection term and separates the effect of plant coefficients on radiation/energy and advection terms. The modified equation was found to improve ET estimates by 8–9% (RMSE: 0.535–0.493, MAD: 0.375–0.343), under non-water limited conditions. For water-limited conditions, errors were significantly reduced. RMSE improved by 37% (0.703–0.440) and MAD was improved by 31% (0.429–0.294).

A water balance based, spatiotemporal evaluation of terrestrial evapotranspiration products across the contiguous United States.

Accurate gridded estimates of evapotranspiration (ET) are essential to the analysis of terrestrial water budgets. In this study, ET estimates from three gridded energy-balance based products (ETEB) with independent model formations and data forcings are evaluated for their ability to capture long term climatology and inter-annual variability in ET derived from a terrestrial water budget (ETWB) for 671 gaged basins across the CONUS. All three ETEB products have low spatial bias and accurately capture inter-annual variability of ETWB in the central US, where ETEB and ancillary estimates of change in total surface water storage (ΔTWS) from the GRACE satellite project appear to close terrestrial water budgets. In humid regions, ETEB products exhibit higher long-term bias, and the covariability of ETEB and ETWB decreases significantly. Several factors related to either failure of ETWB, such as errors in ΔTWS and precipitation, or failure of ETEB, such as treatment of snowfall and horizontal heat advection, explain some of these discrepancies. These results mirror and build on conclusions from other studies: on inter-annual timescales, ΔTWS and error in precipitation estimates are non-negligible uncertainties in ET estimates based on a terrestrial water budget, and this confounds their comparison to energy balance ET models. However, there is also evidence that in at least some regions, climate and landscape features may also influence the accuracy and long-term bias of ET estimates from energy balance models, and these potential errors should be considered when using these gridded products in hydrologic applications.

Capture Versus Capture Zones: Clarifying Terminology Related to Sources of Water to Wells.

The term capture, related to the source of water derived from wells, has been used in two distinct yet related contexts by the hydrologic community. The first is a water-budget context, in which capture refers to decreases in the rates of groundwater outflow and (or) increases in the rates of recharge along head-dependent boundaries of an aquifer in response to pumping. The second is a transport context, in which capture zone refers to the specific flowpaths that define the three-dimensional, volumetric portion of a groundwater flow field that discharges to a well. A closely related issue that has become associated with the source of water to wells is streamflow depletion, which refers to the reduction in streamflow caused by pumping, and is a type of capture. Rates of capture and streamflow depletion are calculated by use of water-budget analyses, most often with groundwater-flow models. Transport models, particularly particle-tracking methods, are used to determine capture zones to wells. In general, however, transport methods are not useful for quantifying actual or potential streamflow depletion or other types of capture along aquifer boundaries. To clarify the sometimes subtle differences among these terms, we describe the processes and relations among capture, capture zones, and streamflow depletion, and provide proposed terminology to distinguish among them.

Water Budget Analysis In Shallow Ground Water Regions Using Multiple Temporal Resolutions Data Sets

Bir havzada bulunan su miktari, su temini ve feyezan yonetimi icin cevresel sistemler acisindan onem arz eden iki konudur. Bu noktada, su butcesi analizi havzalardaki suyun hidrometeorolojik dongusu, tasinmasi ve depolanmasini temsil etme ve kullanmaya olanak saglar. Bu calismada, ABD'nin Florida eyaletinde bulunan Guney Broward bolgesindeki kentsel bir havza olan C11 havzasi kullanilmis olup, bu havza uzerindeki yagis, akarsu, evapotranspirasyon, yeralti suyu verileri dikkate alinarak bir su butcesi analizi sunulmustur. Analizde kullanilan butun veriler Guney Florida Su yonetimi Bolgesi (SFWMD) hidrometeorolojik veritabanindan (DBHYDRO) elde edilmistir. Sonuclar depolama alanindaki hatalarin zamansal cozunurlukteki artisla ters orantili olarak degistigini gostermektedir. Elde edilen veriler, yillik su butcesi analiziyle en tutarli sonuclarin elde edildigini ve yaklasik olarak toplam akisin yuzde 10' una karsilik geldigini gostermektedir. Ayrica, az yagis alan sezondaki hatalarin diger aylara kiyasla daha uygun oldugu gozlemlenmistir.

Assessment of water balance for a forest dominated coastal river basin in India using a semi distributed hydrological model

Nagavali River plays a major role in supporting agriculture and water supply demands in parts of the Kalahandi, Rayagada and Koraput districts of Odisha and Vizianagaram and Srikakulam districts of Andhra Pradesh. With the increase in demand for water and stress from the climate change, there is a need to understand the water balance of the river basin and suggest suitable measures to improve water resources development and water harvesting. In this study, a semi-distributed model, soil and water assessment tool (SWAT) is used to study the spatio-temporal water balance for the entire basin. The model was calibrated and validated at monthly scale using the observed river discharge at Srikakulam over a period of 15 years from 1985 to 2000. Calibration and Validation results for stream flow are satisfactory on a monthly scale. The seasonal water budget analysis reveals that 70% of the annual rainfall and 74% of the annual runoff occur during the monsoon season. The sensitivity analysis showed that the lateral flow travel time, average slope steepness, curve number, available water capacity of the soil basin are the most sensitive parameters. Further the spatial analysis of the water balance components show that there is considerable difference in the precipitation and streamflow within the basin ranging from 914 to 1319 and 82 to 246 mm respectively. The results from the study provide valuable information for the proposed interlinking projects in the future.

Turbulent Heat Fluxes during an Extreme Lake-Effect Snow Event

Abstract Proper modeling of the turbulent heat fluxes over lakes is critical for accurate predictions of lake-effect snowfall (LES). However, model evaluation of such a process has not been possible because of the lack of direct flux measurements over lakes. The authors conducted the first-ever comparison of the turbulent latent and sensible heat fluxes between state-of-the-art numerical models and direct flux measurements over Lake Erie, focusing on a record LES event in southwest New York in November 2014. The model suite consisted of numerical models that were operationally and experimentally used to provide nowcasts and forecasts of weather and lake conditions. The models captured the rise of the observed turbulent heat fluxes, while the peak values varied significantly. This variation resulted in an increased spread of simulated lake temperature and cumulative evaporation as the representation of the model uncertainty. The water budget analysis of the atmospheric model results showed that the majority of the moisture during this event came from lake evaporation rather than a larger synoptic system. The unstructured-grid Finite-Volume Community Ocean Model (FVCOM) simulations, especially those using the Coupled Ocean–Atmosphere Response Experiment (COARE)-Met Flux algorithm, presented better agreement with the observed fluxes likely due to the model’s capability in representing the detailed spatial patterns of the turbulent heat fluxes and the COARE algorithm’s more realistic treatment of the surface boundary layer than those in the other models.

Interdecadal Climate Variations Controlling the Water Level of Lake Qinghai over the Tibetan Plateau

Abstract Using observed and reanalysis data, the pronounced interdecadal variations of Lake Qinghai (LQH) water levels and associated climate factors were diagnosed. From the 1960s to the early 2000s, the water level of LQH in the Tibetan Plateau has experienced a continual decline of 3 m but has since increased considerably. A water budget analysis of the LQH watershed suggested that the water vapor flux divergence is the dominant atmospheric process modulating precipitation and subsequently the lake volume change . The marked interdecadal variability in and was found to be related to the North Pacific (NP) and Pacific decadal oscillation (PDO) modes during the cold season (November–March). Through empirical orthogonal function (EOF) and regression analyses, the water vapor sink over the LQH watershed also responds significantly to the summer Eurasian wave train modulated by the low-frequency variability associated with the cold season NP and PDO modes. Removal of these variability modes (NP, PDO, and the Eurasian wave train) led to a residual uptrend in the hydrological variables of , , and precipitation, corresponding to the net water level increase. Attribution analysis using the Coupled Model Intercomparison Project phase 5 (CMIP5) single-forcing experiments shows that the simulations driven by greenhouse gas forcing produced a significant increase in the LQH precipitation, while anthropogenic aerosols generated a minor wetting trend as well.

Comparison of evaporation rate on open water bodies: energy balance estimate versus measured pan

Abstract Much attention has been paid to establish accurately open water evaporation since the lake itself is the largest consumer of water. The aim of this study is to assess the discrepancy in the measured (pan evaporation) and estimated (Penman) evaporation rate, seasonally, based on the results from a 37-year energy budget analysis of Lake Burrumbeet, Australia. The detailed analysis of meteorological data showed that evaporation is fully radiation driven and that the effect of wind is minimal. Sensitivity analysis shows that evaporation estimation is more sensitive to shortwave radiation followed by relative humidity. An increase or decrease of estimated shortwave radiation by 10% could result in an increase or decrease of estimated evaporation up to 18%. The Penman combination method is relatively the least sensitive to wind speed but could bring a significant effect on the lake level fluctuation since a 10% increase of wind speed increases the estimated evaporation by 2.3%. The current analysis highlights the relative roles of radiation, temperature, humidity, and wind speed in modulating the rate of evaporation from the lake surface, by employing an inter-monthly seasonal adjustment factor to the estimated evaporation in the lake water budget analysis, with implications for the inter-monthly variability and short-term trends assessment of water resource through various meteorological parameters.

Regional Climate Change Impacts on Irrigation Vulnerable Season Shifts in Agricultural Water Availability for South Korea

Reservoirs are principal water resources that supply irrigation water to paddy fields and play an important role in water resources management in South Korea. For optimal irrigation reservoir operation and management, it is necessary to determine the duration of irrigation water shortages. Management of reservoir operation and irrigation scheduling should take into consideration essential variables that include the water supply in a reservoir and the water demand in the associated irrigation district. The agricultural water supply and demand show different patterns based on the variability and uncertainty of meteorological and hydrological phenomena. The duration of excessive water supply can be quantitatively determined through analysis of deviations and changes in the timing of agricultural water supply and demand. In this study, we introduce an approach to assess the vulnerable seasons of paddy irrigation to enable more effective operation and management of reservoirs. The vulnerable seasons were evaluated through comparison of the potential water supply capacity and irrigation water requirements based on water budget analysis via a time series change analysis. We have assessed the changing in the total duration and duration shifts of the vulnerable irrigation seasons for four agricultural reservoirs using past observed data (1981–2010) from meteorological stations maintained by the Korea Meteorological Administration (KMA) and projected climate change scenarios (2011–2100) as depicted by the Representative Concentration Pathways (RCPs) emission scenarios. For irrigation vulnerable seasons under both the RCP 4.5 and RCP 8.5 scenarios, the results showed periods of significant increases in which total vulnerable seasons compared to the historical period; the longest duration of vulnerability occurred during the 2071–2100 period under the RCP 8.5. Identification of the vulnerable seasons for paddy irrigation can be applied in agricultural water management to more effectively manage reservoir operation during irrigation periods with climate changes.

Investigation Anthropogenic Impacts and Climate Factors on Drying up of Urmia Lake using Water Budget and Drought Analysis

The water level of Urmia Lake, the largest inland lake in Iran with maximum water surface area of about 6000 km2, has been shrinking for the last two decades. Although a number of study have been performed to determine drought condition and coastline changes of Urmia Lake, there has not been a detailed study to distinguish anthropogenic effects from climate impacts on the drying of Urmia Lake. In this study, water budget of Urmia Lake and the intensity of drought in the basin were analyzed in the period from 1985 to 2010 and a new hypothesis is proposed to quantify anthropogenic and climate impacts in reducing the volume of Urmia Lake. The results of this study indicate that human impacts on the Lake and its basin are more important than climate factors. Though previous studies assumed that ground water output from Urmia Lake is negligible, the results of this study show the presence of significant groundwater seepage from Urmia Lake. Major changes in the variables that reduced the water level of Urmia Lake were observed since 1998. Anthropogenic impacts and climate factors have roughly 80% and 20% effects on the drying up of Urmia Lake, respectively. Hence, the first step to recover Urmia Lake could be the revision of management surface water, operation of dams and groundwater resources. The second step could be the review and classification of agricultural products grown in the region in terms of water consumption and teach local people the best practice methods for irrigation.

A comprehensive data set of lake surface water temperature over the Tibetan Plateau derived from MODIS LST products 2001\u20132015

Lake surface water temperature (LSWT) is sensitive to long-term changes in thermal structure of lakes and regional air temperature. In the context of global climate change, recent studies showed a significant warming trend of LSWT based on investigating 291 lakes (71% are large lakes, ≥50 km2 each) globally. However, further efforts are needed to examine variation in LSWT at finer regional spatial and temporal scales. The Tibetan Plateau (TP), known as ‘the Roof of the World’ and ‘Asia’s water towers’, exerts large influences on and is sensitive to regional and even global climates. Aiming to examine detailed changing patterns and potential driven mechanisms for temperature variations of lakes across the TP region, this paper presents the first comprehensive data set of 15-year (2001–2015) nighttime and daytime LSWT for 374 lakes (≥10 km2 each), using MODIS (Moderate Resolution Imaging Spectroradiometer) Land Surface Temperature (LST) products as well as four lake boundary shapefiles (i.e., 2002, 2005, 2009, and 2014) derived from Landsat/CBERS/GaoFen-1 satellite images. The data set itself reveals significant information on LSWT and its changes over the TP and is an indispensable variable for numerous applications related to climate change, water budget analysis (particularly lake evaporation), water storage changes, glacier melting and permafrost degradation, etc.

High‐resolution air–sea coupling impact on two heavy precipitation events in the Western Mediterranean

The Mediterranean Sea is an important source of heat and moisture for heavy precipitation events (HPEs). Moreover, the ocean mixed layer (OML) evolves rapidly under such intense events. Whereas short‐term numerical weather prediction systems generally use low‐resolution non‐evolving sea surface temperature (SST), the development of high‐resolution high‐frequency coupled system allows us to fully take into account the fine‐scale interactions between the low‐level atmosphere and the OML which occur during HPEs.The aim of this study is to investigate the impact of fine‐scale air–sea interactions and coupled processes involved during the HPEs which occurred during 12–15 October 2012 (IOP13) and 26–28 October 2012 (IOP16a/b) of the HyMeX first field campaign. For that purpose, the high‐resolution coupled system AROME‐NEMO WMED was developed. This system is based on the 2.5 km‐resolution non‐hydrostatic convection‐permitting atmospheric model AROME‐WMED and the 1/36°‐resolution NEMO‐WMED36 ocean model. The coupling frequency is 1 h. To distinguish the effects due to the change in the initial SST field from that due to the interactive 3D ocean, the coupled run is compared to two AROME‐WMED atmosphere‐only experiments with no SST evolution during the 48 h forecast cycles—one using the AROME‐WMED SST analysis, the second using the SST field of the coupled experiment each day at 0000 UTC. The results of the three experiments re‐assert that the SST initial condition strongly influences the HPE forecast, in terms of intensity and location. With water budget analyses, the significant impact of the ocean interactive evolution on the surface evaporation water supply for HPEs is also highlighted. In cases of strong and intense air–sea exchanges, as in the mistral event of IOP16b, the coupling reproduces the intense and rapid surface cooling and demonstrates the importance of representing the ocean turbulent mixing with entrainment at the OML base.

Modeling the water budget of the Upper Blue Nile basin using the JGrass-NewAge model system and satellite data

Abstract. The Upper Blue Nile basin is one of the most data-scarce regions in developing countries, and hence the hydrological information required for informed decision making in water resource management is limited. The hydrological complexity of the basin, tied with the lack of hydrometeorological data, means that most hydrological studies in the region are either restricted to small subbasins where there are relatively better hydrometeorological data available, or on the whole-basin scale but at very coarse timescales and spatial resolutions. In this study we develop a methodology that can improve the state of the art by using available, but sparse, hydrometeorological data and satellite products to obtain the estimates of all the components of the hydrological cycle (precipitation, evapotranspiration, discharge, and storage). To obtain the water-budget closure, we use the JGrass-NewAge system and various remote sensing products. The satellite product SM2R-CCI is used for obtaining the rainfall inputs, SAF EUMETSAT for cloud cover fraction for proper net radiation estimation, GLEAM for comparison with NewAge-estimated evapotranspiration, and GRACE gravimetry data for comparison of the total water storage amounts available in the whole basin. Results are obtained at daily time steps for the period 1994–2009 (16 years), and they can be used as a reference for any water resource development activities in the region. The overall water-budget analysis shows that precipitation of the basin is 1360 ± 230 mm per year. Evapotranspiration accounts for 56 % of the annual water budget, runoff is 33 %, storage varies from −10 to +17 % of the water budget.