The Characteristics of Variation in Precipitation in Chongqing Urban Area During the Past 100 Years

On the basis of the precipitation data in Chongqing urban area from 1892 to 2009,characteristics of the local annual and seasonal precipitation variation were analyzed with different statistical methods.The main results showed that the annual,spring,summer,and winter precipitation in Chongqing urban area all showed a weak increasing trend during the past 100 years,and autumn precipitation showed a highly significant decreasing trend(r ≤ 0.01).Stage changes of annual and seasonal precipitation were significantly different.Annual precipitation had no obvious sudden change during the past 100 years.Sudden increase in spring,summer and winter precipitation occurred once each,in 1915,1978 and 1956,respectively.A sudden increase in autumn precipitation occurred in 1963,and a sudden decrease in autumn precipitation occurred in 1974.In a period analysis,periodic oscillations were observed,about 3a for annual precipitation,7a and 5a for spring precipitation,3a and 6a for summer precipitation,2a for autumn precipitation and 3a for winter precipitation.