Construction of Albedo Schemes for the Typical Underlying Surface on the Tibetan Plateau Under Snow Free Conditions

Abstract The surface albedo plays a crucial role in regulating the allocation of solar radiation between the surface and atmosphere over the Tibetan Plateau (TP), and significantly influences the heat transfer from the surface to the overlying atmosphere. This study used field observation data to reveal the key factors affecting the albedo of two typical underlying surfaces (bare land, alpine grassland) under snow free conditions. Results show that the solar elevation angle, soil ice content, soil liquid content, and near canopy surface air relative humidity are the primary determinants of albedo for these typical surfaces. Based on these findings, the albedo schemes suitable for the bare land and alpine grassland on the TP have been constructed by considering more comprehensive affecting factors. Evaluation of single‐point simulations at four stations indicates that adopting the new albedo schemes can clearly improve the albedo simulations of Community Land Model version 5 (CLM5) with the root mean square error reduced by ∼10% to ∼60% relative to adopting the original albedo schemes, further leading to the surface net radiation simulations improved and thereafter the warm biases of soil temperature simulations reduced by ∼0.2°C to ∼1°C. Regional simulation verification further confirms that adopting the new albedo schemes in CLM5 can obviously improve the surface net radiation simulations by increasing the albedo simulation accuracy on the TP, thereby mainly reducing the overestimation of surface sensible heat flux and land surface temperature by the original albedo schemes, further resulting in the performance of CLM5 to simulate the TP surface heat conditions enhanced.