The surface downward longwave radiation of the CMIP6 HighResMIP in East Asia offline corrected by the three-dimensional sub-grid terrain longwave radiative effect scheme

Abstract

Terrain significantly regulates surface downward longwave radiation (SDLR). The CMIP6 HighResMIP models without the three-dimensional sub-grid terrain longwave radiative effects (3DSTLRE) produce large SDLR biases over complex terrains. This study applies the 3DSTLRE scheme to correct the SDLR simulated by these models in East Asia and assesses the correction’s effectiveness. Results indicate that the CMIP6 HighResMIP models without the 3DSTLRE clearly underestimate the SDLR over the rugged terrains and the underestimation increases with the sub-grid terrain complexity. The offline correction of 3DSTLRE can evidently improve the SDLR simulations in different seasons, and the improvements increase with the sub-grid terrain complexity. The most significant improvements are observed over the Himalayas, the Tibetan Plateau, the Tianshan Mountains, and the Hengduan Mountains. The relative root mean square error of SDLR simulations over the areas with the most complex sub-grid terrains can be decreased by ∼40% due to the offline correction of 3DSTLRE. Considering the 3DSTLRE may be an efficient way to improve the simulations of the SDLR and surface energy balance over the regions with complex sub-grid terrains.

Keywords

• surface downward longwave radiation
• CMIP6 HighResMIP
• East Asia
• offline correction
• three-dimensional sub-grid terrain longwave radiative effect scheme