Abstract:
Based on the most representative rainfall data during the plum rainy season from 1954 to 2013 in seven Jiangsu riverside cities (Nanjing,Suzhou,Wuxi,Changzhou,Zhenjiang,Yangzhou,Nantong),weve calculated the distribution of feature factors and time sequence using EOF decomposition model.Weve also got the plum rainy seasons main spatial distribution patterns based on the variance contribution of the feature factors.In addition,in the light of the time factor,weve found the distinct regional characteristics with the long-term trend of the precipitation during the plum rainy season and decade change.Weve noticed that during the plum rainy season,before the late 1980 s,the east was water-logging while the west was drought,but after 1990 s,the situation is reverse.Since 1980 s,the rainfall during the plum rainy season in Nanjing,Wuxi,Changzhong and Zhenjiang has a significant change,but there is no obvious change in other areas.In addition,the time-dependent evolution and variance contribution of Meiyu intensity series have been investigated using wavelet energy density technique.The results show that there are significant decade oscillation periods,which last 3—4 years and 13—14 years.The oscillation of the period from the year 1975 to 1980 contributed more to the decade oscillation,and the contribution to the variance of the period of 13—14 years exerted influence on the years after 1970 s.