Relating Precipitating Ice Radiative Effects to Surface Energy Balance and Temperature Biases Over the Tibetan Plateau in Winter

Substantial underestimation of the ice water path, surface radiative fluxes, and surface temperature is identified from the Coupled Model Inter-comparison Project phase 5 models over the boreal winter Tibetan Plateau. It is found that the cold bias is controlled by the biases of surface radiative fluxes, and the underestimated ice water path has significant contribution to the radiation biases. In addition, after removing the impact of snow albedo feedback, the relation between the biases of residual surface temperature and ice water path can be revealed. A set of sensitivity experiments with fully coupled Community Earth System Model version 1 (CESM1) is performed to identify the impact of the precipitating ice radiative effect on biases of the surface energy budget and temperature. When this effect is turned off, more solar radiation can penetrate through the optically thin atmosphere, while much less downward longwave radiation owing to missing of emission from falling snow. The high spatial coherency between the changes in surface radiation budget and surface temperature suggests that the cold bias over the Tibetan Plateau could be partly attributed to deficiency of the total downward radiative flux due to the lack of precipitating ice. The inclusion of the precipitating ice radiative effect can reduce the model biases of surface radiative fluxes and surface temperature.