华北地区汛期降水的一个分析研究

AN ANALYTICAL STUDY ON THE PRECIPITATION IN THE FLOOD PERIOD OVER HUABEI AREA

通过历史资料的分析,本文首先指出华北地区的汛期降水量存在着不同时间尺度的低频变化,其中以准两年周期振荡和周期约为16年的振荡比较明显,而且前者同平流层QBO有一定关系。另外,在汛期多雨年,华北降水量有明显季节内(30—60天)振荡;而在汛期少雨年,降水量的30—60天振荡却不太清楚。 ENSO对华北的汛期降水有重要影响,El Nino年华北汛期雨量平均偏少,仅El Nino年华北汛期平均雨量偏多。El Nino年所出现的大气环流异常是造成华北汛期降水量变化的重要原因。关于高纬度和极区环流对华北汛期降水量的影响也进行了初步探讨。

Based on the analyses in observational data, it is indicated that the precipitation in the flood period over Huabei area has low-frequency oscillations with different time scale. The quasibiennial period variation of precipitations is very obvious and it has close relations with QBO. The 16-year quasi-periodical variation of precipitations is also in existence. It has been found that the precipitations over Huabei area in summer has clear 30-60 day oscillation for the rainy years, while this oscillation is not obvious for the drought years.An important influence of ENSO on the precipitation in the flood period over Huabei area is investigated. In general, the precipitation in the flood period in El Nino year is less than normal, but more in inverse El Nino year. The anomalies of general circulation caused by El Nino is a direct reason to produce anomalous variation of the precipitation. On other hand, the influences of general circulation in the high-latitude and pole area on the precipitation in the flood period over Huabei are discussed in this paper.