Performance of Common Land Model in Simulating the Land Surface Thermal and Hydrological Processes Over China Improved by Including the Sub-Grid Terrain Solar Radiative Effect

Abstract

The sub-grid terrain solar radiative effect (STSRE) significantly affects the heterogeneity of the surface downward solar radiation (SDSR) over mountainous areas, which further exerts remarkable influences on simulations of surface energy budgets and hydrological processes. Given that two thirds of China is mountainous, we have systematically revealed the noticeable STSRE impacts on the performance of the Common Land Model (CoLM) in simulating land surface thermal and hydrological processes over China. Validations indicate that adopting the three dimensional (3D) STSRE scheme clearly improves the CoLM's ability in simulating the land thermal and moist characteristics over China in almost all seasons, and the improvements increase with the terrain complexity increasing. Over the regions with the most rugged terrain, adopting the 3D STSRE scheme can remarkably reduce the overestimated SDSR and thereafter land surface temperature (LST) warm biases in the CoLM with the plane-parallel radiative scheme. The modeled snow cover increases corresponding to the reduced LST with the Taylor score improved the most by 52.84% in summer, and the modeled evapotranspiration (ET) over southeastern Tibet and the Hengduan Mountains is also notably improved in summer. Further analysis indicates that the surface net radiation well corrected by the 3D STSRE scheme firstly reduces the warm biases of LST simulation using the plane-parallel radiative scheme over strong terrain shaded areas, directly leading to the depressed sensible heat flux and ET and more snow accumulation, then the inhibited ET and increased snow accumulation jointly affect the runoff and soil moisture simulations and thereafter latent heat simulation.