VARIATION OF RAINFALL OVER NORTH CHINA AND ITS POSSIBLE CONNECTION TO El NIO
华北降水资源的变化及其与厄尔尼诺的关系

Rainfall resource is very important to social economic system, especi ally to North China which is now facing serious challenge of water shortage. Bas ed on the observational records covering the period from 1951 to present, the ch aracteristics of precipitation changing over North China and its possible connec tion to El Nio were studied using tendency analysis, correlation analysis and wavelet analysis. Results showed that the rainfall in North China had a down te ndency in summer and autumn at a rate of-9.6mm/10a and -4.5mm/10a respectively. And annual precipitation was decreasin g at the rate of -12.9mm/10a. In decadal time scale, abrupt changes were observ ed in the mid 1960s for summer and annual precipitation.Precipitation was signi ficantly less for the decade after about 1985 in contrast to the decade before. The time series showed perio dicities at 2-4, 8, 20 years for summer rainfall and at 2-4, 8 years for autum n rainfall. El Nio had prominent impacts on precipitation of North China,under El Nio condition the rainfall will decrease significantly in summer and autum n, and increase in spring.