1961～2008年华北地区降水变化内在特征分析

Analysis of the Intrinsic Characteristics of Precipitation Change in North China from 1961 to 2008

使用北京、天津、河北和山西的37个气象观测站1961～2008年逐日降水资料,对华北降水内在变化特征进行统计分析。结果表明,受季风影响,华北降水高度集中在夏季,占年降水总量的65.0%。华北多年平均降水日数为76d,夏季为35d。年降水量减少不是由于雨强变化造成的,而主要是由于雨日减少的影响,雨日减少主要发生在夏季,其中夏季暴雨雨日减少造成的雨量减少最为重要。这为改进华北夏季降水预测提供了思路,即要改进华北夏季降水预测技术,应把着眼点放在暴雨过程预报上,应分析是否会出现有利于暴雨发生的环流形势,不应该简单地通过平均环流来预测夏季降水量偏多或偏少。

Based on daily precipitation data of 37 meteorological observation stations from Beijiug, Tianjiu, Hebei, Shanxi during 1961 - 2008, a statistical analysis was conducted on the intrinsic characteristics of precipitation change in North China. The results show that influenced by the monsoon, North China rainfall was highly concentrated in the summer, accounting for 65% of the total annual precipitation. The many years averaged number of days of precipitation in North China was 76 days, summer with 35 days. Reduction of the annual precipitation was not caused by rain intensity changes, but mainly due to the impact of rainy days reduction. Rainy days decrease mainly occurred in the summer and reduced storm days played the most important role. This provided a guideline to improve the summer precipitation prediction in North China , that is, to improve the summer precipitation forecasting techniques, focus should be laid on the heavy rain process forecast to analyze whether there will be conducive circulation situation to the rainstorms occurrence. It was not accurate to simply predict rainfall high or less than normal in summer through averaged circulation.