The Analysis of the Strongest Dragon-boat Rain in GuangDong province in 2008

Using conventional observation data and NCEP/NCAR reanalysis data,physical mechanism affecting weather system and rain-formation, interaction and inter-impact between low and middle latitude weather system of four times heavyrain in GuangdongDragon-boat rainperiod of 2008 were analyzed and diagnosed.The results showed that several strong rain procedures mostly occurred in the background of 500 hPa westly trough actively and the 850 hPa low-eddy moving eastward.The combination of the low-level vorbex which shift eastward and the westerly trough is the major weather slfsterm which produced heavy rain.It was discovered that the Indian cross-equatorial flow,the South China Sea cross-equatorial flow was stronger,which made further south monsoon extremely active,and the vapor was transported by two paths,which provided the plentiful vapor condition forDragon-boat rainperiod in Guangdong;The Subtropical High was weaker and leaning east which was conducive to high-altitude trough of low pressure over the South China,brought instability of atmospheric motion and guided southward of cold air.