Analysis of Simulation on Wintertime Surface Condition in Xinjiang by RegCM4 Model

Based on Comparison with the ERA40 reanalysis, the regional climate model RegCM4.3 simulation on wintertime surface condition in Xinjiang is analyzed. The results show that RegCM4.3 can well simulate the spatial distribution of surface temperature in Xinjiang, which is greatly affected by terrain. The prominent differences in surface thermal properties and strong heterogeneity caused by large topography gradient lead to significant simulation errors. The model realistcally simulates the spatial distribution features of precipitaioon and latent heat flux, both are larger in northern Xinjing than in southern Xinjiang and larger in mountaineous region than in basins. The simulated surface net downward shortwave flux is much larger in central desert than in Tianshan mountain region. Southern and northern Xinjiang are the source and sink of sensible heat flux respectively, which is well reproduced by RegCM4.3. The simulated distribution of snow water equivalent agrees well with precipitation. Meanwhile, the spring snowmelt runoff is also consistent with both snow water equivalent and precipitation. Analysis of the simulation also reveals that the sensible heat flux is underestimated due to the fact that the ground potential temperature is replaced by ground temperature in RegcM4.3. As a result, the sensible heat source in southern Xinjiang is underestimated while the sensible heat sink in northern Xinjiang is overestimated. Additionally, the large simulated bias of spring snowmelt runoff in northern Xinjiang might be attributed to biases of simulated snow and ground temperature.