A joint soil-vegetation-atmospheric modeling procedure of water isotopologues with WRF-Hydro-iso: Implementation and application to present-day climate in Europe and Southern Africa

2021 ◽  
Author(s):  
Joel Arnault ◽  
Gerlinde Jung ◽  
Barbara Haese ◽  
Benjamin Fersch ◽  
Thomas Rummler ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Water Flow ◽  
Southern Africa ◽  
Hydrological Modeling ◽  
Atmospheric Modeling ◽  
Global Network ◽  
Grid Spacing ◽  
Outer Domain ◽  
Terrestrial Water ◽  
Water Isotopologues

<p>Water isotopologues, as natural tracers of the hydrological cycle on Earth, provide a unique way to assess the skill of climate models in representing realistic atmospheric and terrestrial water pathways. In the last decades, many global and regional models have been developed to represent water isotopologues and enable a direct comparison with observed isotopic concentrations. This study presents the recently developed regional model, WRF-Hydro-iso, which is a version of the coupled atmospheric – hydrological modeling system WRF-Hydro enhanced with a joint soil-vegetation-atmospheric description of water isotopologues motions. WRF-Hydro-iso is applied to two regions in Europe and Southern Africa under present climate condition. The setup includes an outer domain with a 10 km grid-spacing, an inner domain with a 5 km grid-spacing, and a subdomain with a 500 m grid spacing that can be coupled with the inner domain in order to represent lateral terrestrial water flow. A 10-year slice is simulated for 2003-2012, using ERA5 reanalyses for the boundary condition. The boundary condition of the isotopic variables is specifically provided with climatological values deduced from a 10-year simulation with the Community Earth System Model Version 1. For both Europe and Southern Africa, WRF-Hydro-iso realistically reproduces the climatological variations of the isotopic concentrations δ<sub>P</sub><sup>18</sup>O and δ<sub>P</sub><sup>2</sup>H from the Global Network of Isotopes in Precipitation. In a sensitivity analysis, it is found that land surface evaporation fractionation increases the isotopic concentrations in the rootzone soil moisture and slightly decreases the isotopic concentrations in precipitation, an effect that is modulated by the change in evaporation – transpiration partitioning caused by lateral terrestrial water flow. The ability of WRF-Hydro-iso to account for a detailed description of terrestrial water transport makes it as a good candidate for the dynamical downscaling of global paleoclimate simulations and for the comparison to isotopic measurements in proxy data such as plant wax fossils.</p>

Contribution of lateral terrestrial water flow to precipitation – A WRF-Hydro ensemble analysis and continental evaporation tagging for Europe

2020 ◽  
Author(s):  
Joel Arnault ◽  
Benjamin Fersch ◽  
Thomas Rummler ◽  
Zhenyu Zhang ◽  
Jianhui Wei ◽  
...  
Keyword(s):  
Water Flow ◽  
Land Surface ◽  
Summer Precipitation ◽  
The State ◽  
Grid Spacing ◽  
Surface Evaporation ◽  
Terrestrial Water ◽  
Grid Points ◽  
Horizontal Grid ◽  
Land Water

<p>Land-atmosphere feedback processes are key components of the Earth climate system. In general, it is questionable to which extend the state of the land surface feeds back to the state of the atmosphere. This question can be addressed with a coupled land surface – atmospheric model, and the realism of the simulated feedbacks can be evaluated with a model-to-observation comparison. This study investigates the particular case of the process chain linking lateral terrestrial water flow, soil moisture, surface evaporation and precipitation. The focus is on summer precipitation in the European region. The study period is set to four months in June-September 2008. The tool to conduct this study is the coupled atmospheric – hydrological model WRF-Hydro, which allows surface and subsurface water routing. For the setup of the atmospheric part, a horizontal grid of 700x500 grid points with a grid spacing of 5 km, that is covering an area of 3500 km x 2500 km, and 50 vertical levels up to 10 hPa is chosen. For the setup of the land water routing, a horizontal grid of 14000x10000 grid points with a grid spacing of 250 m and 4 soil layers down to 2 m depth is chosen. The employed model version includes a surface evaporation tagging procedure in order to quantify the fraction of European precipitation originating from evaporation from all over the European continent. The method consists of generating a set of WRF-Hydro simulations with and without land water routing by using random realizations of the stochastic kinetic energy backscatter scheme, and assess the impact of lateral terrestrial water flow on precipitation with the daily gridded observational dataset for precipitation in Europe (E-OBS). An ensemble size of twenty members is used to disentangle the contribution of two processes responsible for precipitation differences between WRF-Hydro simulations with and without land water routing, namely the changes in surface evaporation and the atmosphere chaotic behavior. It is found that the consideration of lateral terrestrial water flow increases the amount of summer precipitation through enhanced surface evaporation up to 10%, which reduces the bias to E-OBS.</p>

scholarly journals Role of Runoff–Infiltration Partitioning and Resolved Overland Flow on Land–Atmosphere Feedbacks: A Case Study with the WRF-Hydro Coupled Modeling System for West Africa

2016 ◽  
Vol 17 (5) ◽  
pp. 1489-1516 ◽  
Author(s):  
Joel Arnault ◽  
Sven Wagner ◽  
Thomas Rummler ◽  
Benjamin Fersch ◽  
Jan Bliefernicht ◽  
...  
Keyword(s):  
West Africa ◽  
Overland Flow ◽  
River Flow ◽  
Efficiency Coefficient ◽  
Wet Season ◽  
Coupled Modeling ◽  
Study Region ◽  
Outer Domain ◽  
Terrestrial Water

Abstract The analysis of land–atmosphere feedbacks requires detailed representation of land processes in atmospheric models. The focus here is on runoff–infiltration partitioning and resolved overland flow. In the standard version of WRF, runoff–infiltration partitioning is described as a purely vertical process. In WRF-Hydro, runoff is enhanced with lateral water flows. The study region is the Sissili catchment (12 800 km2) in West Africa, and the study period is from March 2003 to February 2004. The WRF setup here includes an outer and inner domain at 10- and 2-km resolution covering the West Africa and Sissili regions, respectively. In this WRF-Hydro setup, the inner domain is coupled with a subgrid at 500-m resolution to compute overland and river flow. Model results are compared with TRMM precipitation, model tree ensemble (MTE) evapotranspiration, Climate Change Initiative (CCI) soil moisture, CRU temperature, and streamflow observation. The role of runoff–infiltration partitioning and resolved overland flow on land–atmosphere feedbacks is addressed with a sensitivity analysis of WRF results to the runoff–infiltration partitioning parameter and a comparison between WRF and WRF-Hydro results, respectively. In the outer domain, precipitation is sensitive to runoff–infiltration partitioning at the scale of the Sissili area (~100 × 100 km2), but not of area A (500 × 2500 km2). In the inner domain, where precipitation patterns are mainly prescribed by lateral boundary conditions, sensitivity is small, but additionally resolved overland flow here clearly increases infiltration and evapotranspiration at the beginning of the wet season when soils are still dry. The WRF-Hydro setup presented here shows potential for joint atmospheric and terrestrial water balance studies and reproduces observed daily discharge with a Nash–Sutcliffe model efficiency coefficient of 0.43.

The efficacy of seasonal terrestrial water storage forecasts for predicting vegetation activity over Africa

2021 ◽  
Author(s):  
Benjamin I Cook ◽  
Kimberly Slinski ◽  
Christa Peters-Lidard ◽  
Amy McNally ◽  
Kristi Arsenault ◽  
...  
Keyword(s):  
Regression Model ◽  
Southern Africa ◽  
Water Storage ◽  
Dry Season ◽  
Forecast Skill ◽  
Terrestrial Water Storage ◽  
Wet Season ◽  
Area Index ◽  
Vegetation Activity ◽  
Terrestrial Water

AbstractTerrestrial water storage (TWS) provides important information on terrestrial hydroclimate and may have value for seasonal forecasting because of its strong persistence. We use the NASA Hydrological Forecast and Analysis System (NHyFAS) to investigate TWS forecast skill over Africa and assess its value for predicting vegetation activity from satellite estimates of leaf area index (LAI). Forecast skill is high over East and Southern Africa, extending up to 3–6 months in some cases, with more modest skill over West Africa. Highest skill generally occurs during the dry season or beginning of the wet season when TWS anomalies from the previous wet season are most likely to carry forward in time. In East Africa, this occurs prior to and during the transition into the spring “Long Rains” from January–March, while in Southern Africa this period of highest skill starts at the beginning of the dry season in April and extends through to the start of the wet season in October. TWS is highly and positively correlated with LAI, and a logistic regression model shows high cross-validation skill in predicting above or below normal LAI using TWS. Combining the LAI regression model with the NHyFAS forecasts, 1-month lead LAI predictions have high accuracy over East and Southern Africa, with reduced but significant skill at 3-month leads over smaller sub-regions. This highlights the potential value of TWS as an additional source of information for seasonal forecasts over Africa, with direct applications to some of the most vulnerable agricultural regions on the continent.

scholarly journals Involving the Navier–Stokes equations in the derivation of boundary conditions for the lattice Boltzmann method

2011 ◽  
Vol 369 (1944) ◽  
pp. 2184-2192 ◽  
Author(s):  
Joris C. G. Verschaeve
Keyword(s):  
Boundary Condition ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Stokes Equations ◽  
Slip Boundary Condition ◽  
Navier Stokes ◽  
Grid Spacing ◽  
Navier Stokes Equations ◽  
Slip Boundary ◽  
Boltzmann Method

By means of the continuity equation of the incompressible Navier–Stokes equations, additional physical arguments for the derivation of a formulation of the no-slip boundary condition for the lattice Boltzmann method for straight walls at rest are obtained. This leads to a boundary condition that is second-order accurate with respect to the grid spacing and conserves mass. In addition, the boundary condition is stable for relaxation frequencies close to two.

scholarly journals Toward continental hydrologic–hydrodynamic modeling in South America

2018 ◽  
Vol 22 (9) ◽  
pp. 4815-4842 ◽  
Author(s):  
Vinícius A. Siqueira ◽  
Rodrigo C. D. Paiva ◽  
Ayan S. Fleischmann ◽  
Fernando M. Fan ◽  
Anderson L. Ruhoff ◽  
...  
Keyword(s):  
South America ◽  
Land Surface ◽  
River Discharge ◽  
Hydrological Modeling ◽  
Water Levels ◽  
Scale Model ◽  
Global Models ◽  
Discharge Data ◽  
Continental Scale ◽  
Terrestrial Water

Abstract. Providing reliable estimates of streamflow and hydrological fluxes is a major challenge for water resources management over national and transnational basins in South America. Global hydrological models and land surface models are a possible solution to simulate the terrestrial water cycle at the continental scale, but issues about parameterization and limitations in representing lowland river systems can place constraints on these models to meet local needs. In an attempt to overcome such limitations, we extended a regional, fully coupled hydrologic–hydrodynamic model (MGB; Modelo hidrológico de Grandes Bacias) to the continental domain of South America and assessed its performance using daily river discharge, water levels from independent sources (in situ, satellite altimetry), estimates of terrestrial water storage (TWS) and evapotranspiration (ET) from remote sensing and other available global datasets. In addition, river discharge was compared with outputs from global models acquired through the eartH2Observe project (HTESSEL/CaMa-Flood, LISFLOOD and WaterGAP3), providing the first cross-scale assessment (regional/continental  ×  global models) that makes use of spatially distributed, daily discharge data. A satisfactory representation of discharge and water levels was obtained (Nash–Sutcliffe efficiency, NSE > 0.6 in 55 % of the cases) and the continental model was able to capture patterns of seasonality and magnitude of TWS and ET, especially over the largest basins of South America. After the comparison with global models, we found that it is possible to obtain considerable improvement on daily river discharge, even by using current global forcing data, just by combining parameterization and better routing physics based on regional experience. Issues about the potential sources of errors related to both global- and continental-scale modeling are discussed, as well as future directions for improving large-scale model applications in this continent. We hope that our study provides important insights to reduce the gap between global and regional hydrological modeling communities.

scholarly journals Computing water flow through complex landscapes – Part 2: Finding hierarchies in depressions and morphological segmentations

2020 ◽  
Vol 8 (2) ◽  
pp. 431-445
Author(s):  
Richard Barnes ◽  
Kerry L. Callaghan ◽  
Andrew D. Wickert
Keyword(s):  
Water Flow ◽  
Hydrological Modeling ◽  
Dynamic Models ◽  
Terrain Analysis ◽  
Flow Paths ◽  
Topographic Complexity ◽  
Morphological Segmentation ◽  
Surface Water Flow ◽  
Digital Elevation ◽  
Flow Through

Abstract. Depressions – inwardly draining regions of digital elevation models – present difficulties for terrain analysis and hydrological modeling. Analogous “depressions” also arise in image processing and morphological segmentation, where they may represent noise, features of interest, or both. Here we provide a new data structure – the depression hierarchy – that captures the full topologic and topographic complexity of depressions in a region. We treat depressions as networks in a way that is analogous to surface-water flow paths, in which individual sub-depressions merge together to form meta-depressions in a process that continues until they begin to drain externally. This hierarchy can be used to selectively fill or breach depressions or to accelerate dynamic models of hydrological flow. Complete, well-commented, open-source code and correctness tests are available on GitHub and Zenodo.

scholarly journals Past terrestrial water storage (1980–2008) in the Amazon Basin reconstructed from GRACE and in situ river gauging data

2011 ◽  
Vol 15 (2) ◽  
pp. 533-546 ◽  
Author(s):  
M. Becker ◽  
B. Meyssignac ◽  
L. Xavier ◽  
A. Cazenave ◽  
R. Alkama ◽  
...  
Keyword(s):  
Large Scale ◽  
Amazon Basin ◽  
Hydrological Modeling ◽  
Water Cycle ◽  
Southern Oscillation ◽  
Water Storage ◽  
Terrestrial Water Storage ◽  
Direct Estimate ◽  
Terrestrial Water

Abstract. Terrestrial water storage (TWS) composed of surface waters, soil moisture, groundwater and snow where appropriate, is a key element of global and continental water cycle. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) space gravimetry mission provides a new tool to measure large-scale TWS variations. However, for the past few decades, direct estimate of TWS variability is accessible from hydrological modeling only. Here we propose a novel approach that combines GRACE-based TWS spatial patterns with multi-decadal-long in situ river level records, to reconstruct past 2-D TWS over a river basin. Results are presented for the Amazon Basin for the period 1980–2008, focusing on the interannual time scale. Results are compared with past TWS estimated by the global hydrological model ISBA-TRIP. Correlations between reconstructed past interannual TWS variability and known climate forcing modes over the region (e.g., El Niño-Southern Oscillation and Pacific Decadal Oscillation) are also estimated. This method offers new perspective for improving our knowledge of past interannual TWS in world river basins where natural climate variability (as opposed to direct anthropogenic forcing) drives TWS variations.

scholarly journals From climatological to small scale applications: Simulating water isotopologues with ICON-ART-Iso (version 2.1)

2017 ◽  
Author(s):  
Johannes Eckstein ◽  
Roland Ruhnke ◽  
Stephan Pfahl ◽  
Emanuel Christner ◽  
Christoph Dyroff ◽  
...  
Keyword(s):  
Water Cycle ◽  
Global Network ◽  
Small Scale ◽  
Seasonal Cycles ◽  
Flexible Tool ◽  
Modelling Framework ◽  
Daily Cycles ◽  
High Flexibility ◽  
Water Isotopologues ◽  
Δd And Δ18o

Abstract. We present the new isotope enabled model ICON-ART-Iso. The physics of the global ICOsahedral Nonhydrostatic (ICON) modelling framework have been extended to simulate passive moisture tracers and the stable isotopologues HDO and H218O. The extension builds on the infrastructure provided by ICON-ART, which allows a high flexibility with respect to the number of related water tracers that are simulated. The physics of isotopologue fractionation follow the model COSMOiso. First, we present a detailed description of the physics of fractionation that have been implemented in the model. The model is then evaluated by comparing with measurements in precipitation and vapor representing a range of temporal scales. A multi annual simulation is compared to observations of the isotopologues in precipitation taken from the station network GNIP (Global Network for Isotopes in Precipitation). ICON-ART-Iso is able to reasonably simulate the seasonal cycles in δD and δ18O as observed at the GNIP stations. In a comparison with IASI satellite retrievals, the seasonal and daily cycles in the isotopologue content of vapor are examined for different regions in the free troposphere. On a small spatial and temporal scale, ICON-ART-Iso is used to simulate the period of two flights of the IAGOS-CARIBIC aircraft in September 2010, which sampled air in the tropopause level influenced by Hurricane Igor. The general features of this sample as well as all of tropical data available from IAGOS-CARIBIC are captured by the model. The study demonstrates that ICON-ART-Iso is a flexible tool to analyze the water cycle of ICON. It is capable of simulating tagged water as well as the isotopologues HDO and H218O.

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