对华北地区１９５１年以来的降水测站记录进行了趋势分析、相关分析和小波分析。发现４７年来,华北夏季和秋季降水都有明显的减少趋势。夏季和年总降水在１９６４年前后发生了一次明显的变化,以后降水显著减少。１９８５年左右,秋季降水也发生了一次显著减少的变化。夏季华北降水变化的周期主要集中于２～４年、８年左右和２０年左右。秋季最突出的周期是２～４年和８年左右。厄尔尼诺对华北降水的变化有重要影响,发生厄尔尼诺时,华北春季降水偏多,夏季和秋季降水显著偏少。冬季关系不显著。发生厄尔尼诺的次年春季,华北降水偏多。

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.