ANALYSIS ON BACKGROUND OF CLIMATIC VARIATION FOR EXTREMELY RAINY OVER THE MIDDLE REACHES OF THE CHANGJIANG RIVER IN THE 1990S

The major characteristics of precipitation over the middle reaches of Changjiang River during summer in the 1990s are analyzed. Using wavelet transform technology, the multiple time scale variations including inter-annual, inter-decade and long-term trends for summer rainfall in main regions over the middle reaches of Changjiang River and its related physical factors such as sea surface temperature in the eastern equator, the western Pacific Subtropic High, and summer monsoon of the South China Sea are analyzed. The results reveal that the extreme summer raininess in 1990s over the middle reaches of Changjiang River has favorable background of climatic variation.