The effects of the land-surface process parameterization of the RegCM4 on climate simulation in East Asia

Two 44-year numerical simulations in East Asia by the regional climate model RegCM4.0 using its land-surface schemes， CLM3.5 and BATS1e were conducted to investigate the effects of land surface process parameterization schemes in a regional climate model on the regional climatic simulation. The two simulations were named as R-BATS and R-CLM，corresponding to CLM3.5 and BATS1e, respectively. The results revealed that the simulated surface air temperature from R CLM was 3.6℃ higher in average, with its decreased root mean square error for 44% compared to that of R-BATS and higher differences appeared in South and Northwest China；the simulated precipitation by R-CLM was 0.17 mm/d less，with its root mean square error decreased for 6.9% and higher differences appeared in South and Northeast China；and the simulated 10 cm soil moisture by R-CLM was 0.008 m3/m3 wetter and higher differences appeared in the regions of the middle and high latitudes. Further analysis revealed that less evapotranspiration and runoff simulated by R-CLM induced its higher soil moisture in the regions of middle and high latitudes，suggesting that further improvement in runoff generation mechanism overthere is needed. More absorbed solar flux and weaker latent flux also induced the higher surface air temperature in R-CLM. Besides， weaker evapotranspiration and higher surface temperatures also induced changes in the general circulation，causing weaker water vapor transport in vertical and horizontal directions and less atmospheric precipitable water. As a result， less precipitation was simulated in most areas including South and Northeast China， which further affected the surface air temperature in some extent owing to more solar flux into land surface.