The CO2-induced sensible heat changes over the Tibetan Plateau from November to April

Abstract

Based on the monthly outputs of the Couple Model Intercomparison Project phase 5 (CMIP5), the present study examines the contributions of direct and indirect effects of CO2 to the response of the sensible heat (SH) over the Tibetan Plateau (TP). Under global warming, the TP SH features an uniform increase during November–April (NDJFMA). During NDJFMA, the SH change over the TP can be mainly attributed to the uniform SST increase induced by CO2 increasing. This uniform SST increase warms the atmosphere. In turn, it leads to: (1) reduction in snowfall over the TP, with maximum over south TP; (2) increased snowmelt mainly above 3000 m and decreased snowmelt near or south of 3000 m elevation south of TP. The net effects of snowfall and snowmelt are towards the reduction of the snow cover over the TP, which may alter the snow-albedo feedback. Consequently, more solar radiation is absorbed by the TP surface, and the TP surface warms. The surface–air temperature difference increases, which leads to the increase in SH. In addition, the enhancement of the SH offsets the increase in absorbed solar radiation and balances the radiation budget. On the above processes, the SST pattern slightly cancels out the TP SH increase; the contributions of CO2 direct radiative effect and residual terms are relatively small. Over the grids with elevations no less than 3000 m, the averaged changes are generally linear.