Lateral terrestrial water flow contribution to summer precipitation at continental scale – A comparison between Europe and West Africa with WRF‐Hydro‐tag ensembles

Abstract

It is well accepted that summer precipitation can be altered by soil moisture condition. Coupled land surfaceatmospheric models have been routinely used to quantify soil moistureprecipitation feedback processes. However, most of the land surface models (LSMs) assume a vertical soil water transport and neglect lateral terrestrial water flow at the surface and in the subsurface, which potentially reduces the realism of the simulated soil moistureprecipitation feedback. In this study, the contribution of lateral terrestrial water flow to summer precipitation is assessed in two different climatic regions, Europe and West Africa, for the period June-September 2008. A version of the coupled atmospheric-hydrological model WRF-Hydro with an option to tag and trace land surface evaporation in the modelled atmosphere, named WRF-Hydro-tag, is employed. An ensemble of 30 simulations with terrestrial routing and 30 simulations without terrestrial routing is generated with random realizations of turbulent energy with the stochastic kinetic energy backscatter scheme, for both Europe and West Africa. The ensemble size allows to extract random noise from continental-scale averaged modelled precipitation. It is found that lateral terrestrial water flow increases the relative contribution of land surface evaporation to precipitation by 3.6% in Europe and 5.6% in West Africa, which enhances a positive soil moistureprecipitation feedback and generates more uncertainty in modelled precipitation, as diagnosed by a slight increase in normalized ensemble spread. This study demonstrates the small but non-negligible contribution of lateral terrestrial water flow to precipitation at continental scale.

Precipitation Over Southern Africa: Moisture Sources and Isotopic Composition

“…These estimates of continental recycling appears to be high compared to previous estimates for other African regions (e.g., Arnault et al., 2021), which might point to potential biases in the Lagrangian source analysis. However, a previous intercomparison study between different methodologies by Winschall et al.…”

“…These estimates of continental recycling appears to be high compared to previous estimates for other African regions (e.g., Arnault et al, 2021), which might point to potential biases in the Lagrangian source analysis. However, a previous intercomparison study between different methodologies by Winschall et al (2014) has shown that, at least for one case study, our trajectory method yields similar results as other numerical water tagging approaches and that the methodological uncertainties associated with the latter can also be large.…”

A Joint Soil‐Vegetation‐Atmospheric Modeling Procedure of Water Isotopologues: Implementation and Application to Different Climate Zones With WRF‐Hydro‐Iso

“…The choice of WSM6, ACM2, Noah-MP, and waiving of cumulus parameterization is a constraint of WRF-Hydro-iso in its current version. It is noted that this physics setup with a grid-spacing of 5 km proved to give reasonable results for summer precipitation in Europe and West Africa (Arnault et al, 2021).…”

“…As in Arnault et al (2021), the version of WRF-Hydro-tag considered in this study is based on the WRF version 4.0 and the hydrological module of WRF-Hydro version 5.0, and the selected physics parameterization options are the six-class WSM6 microphysics scheme of Hong and Lim (2006), the ACM2 atmospheric turbulence scheme of Pleim (2007), and the Noah-MP community Noah land surface model (LSM) with multi-parameterization options of Niu et al (2011). WRF-Hydro-tag can be run with subsurface, overland, and channel flow routing, as well as a bucket model to estimate baseflow (Gochis et al, 2018).…”

Preface – special issue on “coupled atmosphere‐hydrological processes: Novel system developments and cross‐compartment evaluations”

“…Indirectly, indications of possible hydrological impact produced by larger‐scale (continental) application of a fully coupled approach were provided by Arnault et al (2021), who, however, detected a slight precipitation increase. The atmosphere‐land‐ocean coupled system applied by Lewis and Dadson (2021) over the whole United Kingdom showed its ability to predict broad‐scale features of river streamflow even without using proper calibration procedures.…”