20世纪80和90年代华北干旱特征及成因分析

Causes and Comparison of the Droughts of North China in 1980′s and 1990′s

在全球气候变暖背景下,20世纪80年代和90年代几乎有一半的年份出现干旱,90年代华北的干旱频率比80年代更高。本文从干旱基本状况、干旱强度和干旱空间分布出发,对华北地区这两个年代的干旱进行了比较,并从对全球气候变暖的响应和大气环流场特征等方面,探讨了这两个年代干旱的成因。研究表明,在干旱强度和空间分布上,90年代明显强于80年代。对全球气候变暖的响应90年代明显强于80年代,表现了更显著的增暖趋势。80年代的干旱年中北极涛动显著增强,中高纬度地区为气压正距平带控制;90年代的干旱年中北半球中高纬度地区为正负距平波列相间分布,存在EU和PNA遥相关型。本文还定义了西伯利亚高压指数,该指数90年代显著高于80年代,且与华北地区降水显著相关,可以作为华北地区旱涝预测的指标。

The drought year frequency is more and more in North China, under the global warming, there are almost half of years in the 1980′s and 1990′s to drought. From drought conditions, the spatial patterns and intensities of drought, the droughts in North China between 1980′s and 1990′s are compared. Some possible causes linked to the global climatic warming and to atmospheric general circulation over the Northern Hemisphere were discussed. The results indicated that not only the characteristics of drought and spatial patterns of precipitation anomaly in the 1990′s and in the 1980′s were different, but the intensity of the 1990′s were higher than the 1980′s, that the responses of droughts of the 1990′s coincidence with the global climatic warming were higher than the 1980′s, and that atmospheric general circulation of 500 hPa for the drought years in the 1980′s and 1990′s existed differently, in which Arctic Oscillation （AO） produced many of the droughts in the 1980′s, but in the 1990′s, the droughts might have been linked to EU and PNA teleconnection. The Siberian High Index （Ih） was defined, the Ih of the 1990′s were higher than the 1980′s, and related significantly with the precipitation, so that spring and summer Ih can be as a forecasting index for precipitation in North China.