Simulation of Topography Effects on the Shortwave Radiation over the Eastern Slope of the Tibet Plateau

In this study, a precipitation case happing from Aug. 16 to 17, 2012 was simulated by using Weather Research and Forecasting model 3. 5 (WRFV3.5) to investigate the shortwave radiation effect of topographic slope angel, aspect and shading (ESAS) over eastern slope of the Tibetan Plateau (TP). Firstly, the shortwave radiation forcing derived by ESAS was estimated, and the results show that the bigger the slope angle is, the higher the forcing is, and the westward slopes will produce negative forcing while the eastward slopes can induce positive forcing. The forcing can exceed-32 and 20 W m^-2 respectively. It is different that the variation of net shortwave radiation flux at surface shows a southeasterly shift caused by shading effect from the eastern slope of TP (ESTP) toward the Sichuan Basin (SCB). But its spatial distribution even through shifting to the SCB is still similar to slope angle and aspect of the ESTP. Furthermore, the distributions of variations of land surface heat flux and ground temperature in daytime agree well with the changes of net shortwave radiation flux:they all have an own high values belt like the adjacence of the TP and SCB in the SCB. In the night, the changes of surface heat flux represent the familiar features of distribute and the location of high-value areas with declining extent comparing with those in daytime. It can be concluded that the impact of net shortwave radiation flux changes on various heat flux at surface due to the ESAS will continue to night. Both of the changes of vapor water mixing ratio and wind field have the distribution pattern with a high values belt similar to changes of latent heat flux, especially in nighttime. The increase (decrease) of latent heat flux can improve (reduce) the wind speed and finally results in the changes of precipitations.