CLIMATIC VARIATION OFMEIYU IN THE MIDDLE-LOWER REACHES OF CHANGJIANG RIVER DURING 1885 —2000

The decadal scale variation characteristics of the Meiyu (plum rains) time series in the middle and lower reaches of the Changjiang River during 1885—2000 were investigated by using statistical technique. Including maximum entropy spectrum, cross spectrum and abrupt change analysis etc. It is found that: ①There exist a significant positive correlation between the Meiyu rainfall and Meiyu duration and the ending date of Meiyu. ② The main periodic length of Meiyu series are three years, six years and eight years, which are related to the 100 hPa geopotential height over the low latitude, tropical systems and the variation of global land temperature respectively. ③ The 6-year period of the Meiyu duration, onset date and ending date of Meiyu are controlled by the same climatic factors, but the 3-year period of the Meiyu probably are influenced by the different climatic factors. ④ Six different climate phases are identified in the Meiyu time series for recent 116 years (1885—2000).