西北地区东部干旱半干旱区极端降水事件的变化

应用面积权重方法,利用西北地区东部80个测站1960-2000年的资料,对降水的变化及极端降水事件进行了分析。结果表明:西北区东部的气候在近十几年变得更加极端。降水量虽然没有一致的增加或减少的趋势,但自从1990年开始,降水距平百分率低于气候平均值,变化异常;降水异常偏多的区域呈减少趋势,到20世纪90年代中期以后,就几乎没有出现过降水异常偏多的区域;1960-1962年连续3年降水异常偏少的情况是近40a来少见的,这种偏少主要发生在干旱地区;90年代的异常偏少则是全区域的,特别是在湿润、半湿润地区,降水偏少尤其明显;1997年降水偏少最为明显,偏少的区域达20%以上。而在这种气候背景下,90年代极端降水事件并没有减少。

Change of Extreme Precipitation Events in Arid and Semi-Arid Regions in the East of Northwest China

In this article,area-averaged total precipitation,extremely heavy 1-day precipitation events with area weighted method have been analyzed for the east of Northwest China(ENWC).The result supports the notion that the climate of the ENWC has been becoming more extreme in recent years.Although there is an absence of a monotonically increasing or decreasing trend,the change of precipitation is extreme,since about 1990 it has become below the 30-year mean.The area where precipitation is severe moisture surplus has been decreased and disappeared after the middle of 1990s.The case as that very severe drought from 1960 to 1962 was rare in last 40 years,which mainly occurred in drought area.Severe drought during 1990s occurred in all area,especially in moisture area.In 1997,it is the most extreme during last 10 years;nearly more than 20% of the area on average is in severe drought,drought events occurred in spring,summer and autumn.Nevertheless,the extremely heavy precipitation events did not decrease on this background.