Study On Tropical Cyclone Precipitation In East China

Using the Advanced Objective Synoptic Analysis Technique(AOSAT),the annual Tropical Cyclone Precipitation(TCP)is partitioned from 78 station daily observations in East China during 1957-2004.Firstly,using statistical methods,the spatial and temporal distributions of TCP and its correlative characteristics in East China have been presented.Generally speaking,time series of TCP,the number of TC heavy rain events,frequency of influencing TCs,and TC influencing days in East China show slightly decreasing trends,although these trends are not statistically significant.Further researches reveal that the correlationship between TCP and the number of TC heavy rain events is the best,and the volume of TC heavy rain is the principal part of TCP in East China.TCP in different regions are always distinct.Southeastern coastland suffers much more TCP than Northwestern inland in East China.The spatial distribution of the first principal component of Empirical Orthogonal Function(EOF)expansion of TCP in East China stands for the coincident variations,while the second and the third principal component of EOF declare the east to west and the north to south differences respectively.Subsequently,with the help of wavelet analysis,time series of annual TCP in East China is analyzed.The results show that the variation of TCP in East China is mainly based on the 10～15 years interdecal variation before the year 1985,while the variation is primarily based on the 2～5 years interannual variation after 1985.These phenomena are perhaps induced by the warming climate after the later 1980s.Finally,the abnormal of SST and general circulation between different periods have been investigated with band-pass filter,EOF expasion,resultant analysis,and t-test methods.The conclusions reveal that,there are different reasons causing interannual and interdecadal variations of TCP.The interdecadal variations attribute to the PDO phenomenon.Changes of TC steering current induced by the abnormal of SST influence TCs tracks,as a result TCP in East China alters. And there is a relationship between the abnormal of SST in the Equatorial Central-Eastern Pacific and the interannual variations of TCP.Further examinations denote that East Asia-Pacific(EAP) Teleconnection caused by the abnormal of SST in the Equatorial Central-Eastern Pacific changes the circulation over Western North Pacific Ocean,therefore the frequency of annual TC formation changes.The conclousin denotes that the number of TC genesis is the main reason for the interannual variations of TCP in East China.