AN ANALYSIS ON INTERDECADAL VARIATIONS OF TROPICAL CYCLONE PRECIPITATION IN GUANGDONG PROVINCE OF CHINA

The interdecadal variations of tropical cyclones(TCs) and their precipitation over Guangdong Province are investigated using the observational data of TCs and precipitation from 26 observational stations in the province from 1951 to 2005.The results show that the TCs precipitation shows an oscillation with a peak value of about 25 years,with both the numbers of the Guangdong-influencing TCs and TCs formed in the western North Pacific oscillating with a peak value of about 23 years.The correlations are highly positive between the interdecadal variation of TC precipitation over the province and these numbers.The interdecadal variation of TC precipitation in the province shows significant negative correlations with the interdecadal variation of annual mean SST in some parts of the western North Pacific and the interdecadal variation of annual mean 500 hPa geopotential heights in some parts of the middle and high latitudes over the North Pacific.In general,there are high mean SSTs on the equator from central to eastern Pacific,low mean SSTs in the middle and high latitudes over the North Pacific and a main strong East Asian trough over the North Pacific in the period of less TC precipitation as compared with the period of more TC precipitation over the province.

NUMERICAL SIMULATION STUDY OF CLOUD INTERACTION AND FORMATION MECHANISM OF HEAVY RAIN IN MIXED CONVECTIVE-STRATIFORM CLOUD

Using the numerical model of mixed convective-stratiform clouds(MCS)in the paper(Hong 1997)and the averaged stratification of torrential rain processes,the evolution processes, interaction of the two kinds of clouds,structure and the precipitation features in the MCS to produce heavy rain are simulated and studied,and the physical reasons of producing torrential rain are analysed.The results indicate that the stratiform cloud surrounding the convective cloud becomes weakened and dissipates in the developing and enhancing of the convective cloud,and the rainfall rate and water content in the stratiform cloud increase as the distance from the convective cloud becomes larger.The numerical experiments find out that the stratiform cloud provides a benificial developing environment for the convective cloud,i.e.,the saturated environment and the convergence field in the stratiform cloud help to lengthen the life cycle of the convective cloud, produce sustained rainfall with high intensity and intermittent precipitation with ultra-high intensity.These and the ice phase microphysical processes are the main factors for the torrential rain formation and the MCS is a very effective precipitation system.