Analyses of heavy rainfall process in Yunnan influenced by the typhoon “Kaitak”

Based on the reanalysis data by the NCEP/NCAR and conventional observation data by meteorological observatory of Yunnan,the heavy-hard rain and local cloudburst in the south and west of Yunnan from 20:00 17 to 08:00 20 Aug 2012 caused by the typhoon “Kaitak” moving westward was analyzed.The result indicated that firstly,the circulation background of typhoon “Kaitak” moving westward was the west Pacific subtropical high enhanced and stretching westward and the west phase of the south Asia high.The heavy rainfall in the south and west of Yunnan was caused by the easterly jet of typhoon northern periphery.Second,it was found that the sufficient moisture in the air,low level convergence and high level divergence,pressure system onset and progression,severe ascending air and unstable energy were beneficial for causing heavy rain in the south of Yunnan by specific humidity,relative humidity,vertical,velocity,divergence and index K in heavy rain area(21°—23°N，98°—106°E).Third,further analyzes by vapor flux and vapor flux divergence indicated that there was a powerful moisture channel,which South China Sea water vapor was transported to the southeast and south of Yunnan by the typhoon east southerly current,so the water vapor vonvergence of high value was in the central and south of Yunnan.