Assessing the interactions of atmosphere and land surface over South Africa with convective-permitting coupled atmospheric-hydrological modeling

Land degradation, as a major issue in South Africa, undermines water resources and land potential productivity, and threatens the ecosystem biodiversity and human activities. In the scope of accurately assessing the land degradation processes in multi-use landscapes, the atmosphere-land surface relations and the dynamics of land surface state variabilities need to be addressed in a detail. This requires Earth System modeling approaches jointly considering high-resolution atmospheric modeling, land surface and hydrological modeling frameworks. This study investigates the atmosphere-land interactions and land surface water-energy budget for South Africa using the Earth System Model WRF-Hydro. WRF-Hydro is the fully coupled atmosphere-land surface-hydrology modeling system, which enhances the Weather Research and Forecasting model with the overland and subsurface water routing processes. In the WRF-Hydro modeling setup, the atmospheric part is configured in a convection-permitting spatial resolution at 4 km, with horizontal grids of 650 × 500 points, covering area of Southern Africa. In the land surface, the gridded hydrological processes are routed on a 400 m fine hydrological subgrid, within a soil depth of 2 m. In this study, we perform the coupled simulation for the year of 2010 and show the validation of modeling results with multiple reference datasets. The water-energy budget in the land surface from coupled WRF-Hydro simulation is assessed on 22 primary hydrological drainage regions. Model results show that coupled atmospheric-hydrological modeling is able to represent the regional water and energy budget, and to resolve atmosphere-land surface interactions. This allows the further usage of the coupled atmospheric-hydrological modeling in the context of land degradation studies, e.g. under different land-use scenarios.