江西2012年5月12日大暴雨过程水汽输送分析

利用NCEP 1°×1°再分析资料、常规气象观测资料和WRF中尺度数值模式,对2012年5月12日江西出现的大暴雨天气水汽输送的过程进行分析。结果表明,从大尺度分析,此次暴雨过程的水汽输送特征并不典型,比湿、水汽通量、水汽通量散度、整层水汽输送等均不能满足江西出现暴雨时应该达到的水汽条件;但模拟的中小尺度水汽指数能够满足江西发生暴雨的水汽条件。此次暴雨过程的水汽主要来自南海地区。暴雨出现的区域与整层水汽大值区的水平梯度最大处相吻合。当整层水汽输送值较小时,水汽输送主要集中在中低层,但当整层水汽输送值较大时,水汽输送的高度高度超过500 hPa高度层,仅分析500 hPa高度层以下的水汽输送对暴雨预报会造成一定的误差。

ANALYSIS ON WATER VAPOR TRANSPORT OF A HEAVY RAINFALL PROCESS IN JIANGXI

Based on NCEP/NCAR reanalysis data and conventional observation data,WRF model is used to analyze the water vapor transport of a heavy rainfall process occurred in Jiangxi on May 12,2012.The results show that the water vapor transport of the rainstorm process is not typical,the specific humidity,vapor flux,vapor flux divergence and the vertically integrated water vapor flux are all not satisfied the rainstorm threshold in Jiangxi,however,the simulated vapor indexes can meet the moisture condition for rainstorm in Jiangxi.The vapor source related to the heavy rainfall comes from the South China Sea.The heavy rainfall region locates at the left of the water vapor band and closes to the wind shear line.According to the simulated result of WRF,the heavy rainfall occurs in the maximum gradient of water flux and the entire water vapor transportation band presents the distribution from southwest to northeast.