Evaluation on simulation of summertime atmospheric water vapor transport over North China using a regional airsea coupled model and its comparison with the regional climate model.

Evaluation on simulation of the summer time atmospheric water vapor transport an d the precipitable water over North China is carried out by using a regional air-sea coupled model RegCM3POM and its comparison with the NCEP/NCAR reanalysis data set. The difference between the regional air-sea coupled model and the re gional climate model is also investigated. The results show that, RegCM3POM ha s a considerable improvement on the simulation of the atmospheric water vapor tr ansport compared with RegCM3. Both of the regional air sea coupled model and th e regional climate model can reproduce the climatological distribution of summer time precipitable water and atmospheric water vapor transport over East Asia. The simulation of the regional airsea coupled model is more reasonable and close r to the observation in the lower and middle troposphere, compared with that of the regional climate model. The climatological characteristics of atmospheric wa ter vapor transport in the vertical profile and its horizontal budget over four boundaries of North China are more reasonable in the coupled model than those in the uncoupled model. The anomalous distribution of atmospheric water vapor tran sport associated with anomalous summer rainfall over North China is also reprodu ced in the regional air sea coupled model. The sources of anomalous atmospheric water vapor transport in the regional airsea coupled model are basically in agreement with the observation. The results of the regional airsea coupled mod el is dramatically improved compared with those of the regional climate model, e specially in the region north of 20°N. However, it is noticeable that the bias of the climatological summertime precipitable water over the low latitude oceani c region in the regional airsea coupled model is larger than that in the regio nal climate model. Compared with the observation, the simulation of the atmosphe ric water vapor transport from the Bay of Bengal is weaker, and the atmospheric water vapor transport along the western part of the Western Pacific subtropical high is stronger in the regional airsea coupled model. The anomalous distribut ion of atmospheric water vapor transport associated with anomalous summer rainfa ll over North China also has a conspicuous bias over the low latitude oceanicre gion in the regional air sea coupled model RegCM3 POM.