【摘要】 利用西北五省区137个测站的1961-2009年逐月降水量资料计算标准化降水指数(SPI),统计了逐月、春末夏初、初夏、夏季及秋季的干旱、重旱、特旱的频率及面积率,分析其时空变化特征.结果表明:新疆北部、青海的中部及甘肃河西是西北地区干旱频率较高的区域,干旱频率在15个月以上,新疆南部除个别月份干旱发生频率较高外,总体干旱发生频率较低;干旱发生区域随月份有由南到北、由西向东变化的趋势;除新疆、青海、及甘肃个别区域重旱频率超过5月外,其他区域基本上都在5月以下;新疆南部重旱频率仍然较低;夏季发生范围高于其他季节;新疆北部、甘肃河西是特旱的高发区.不同等级的月及季节干旱面积率其逐年变化具有相似的特征,西北干旱面积率的变化总体上可以分为3个阶段:1961-1980年干旱面积率比较高,平均在35%左右;1981-1990年为转折期,干旱面积率下降到15%左右;而1991-2009年为稳定期,干旱面积率变化不大.全球气候变暖导致西北地区降水量、冰川融水量、河川径流量增加和湖泊水位上升、面积扩大,是1987年以来干旱面积率下降的原因.更多还原

【Abstract】 In this paper,monthly precipitation data from 137meteorological stations in Northwest China from 1961to 2009 were used to calculate the standardized precipitation index(SPI).Then the frequencies and area ratios of the light drought,severe drought and extra severe drought,monthly and in the four drought durations(late spring,early summer,summer and autumn),were calculated.Their spatial and temporal characteristics were also analyzed.The results show that(1)northern Xinjiang region,central Qinghai and Hexi Corridor of Gansu are the regions with highest drought frequencies,more than 15months.While in southern Xinjiang region the drought frequency is lower,except for individual months;locations of the drought area has an move forward trend from south to north,from west to east with months;(2)the severe drought frequencies of the most parts of Northeast China are less than 5months,expect for individual areas in Xinjiang,Qinghai and Gansu.The frequency in southern Xinjiang region is still lower.The frequency in summer is higher than that in the other seasons.Northern Xinjiang region and Hexi Corridor of Gansu are places with extra severe drought;(3)drought area ratios of different grades has the similar annual changing characteristics,which generally can be divided into three periods:high drought frequency period(the average drought rate was about 35%) from 1961to 1980,transition period(the drought rate was about 15%)from 1981to 1990and stabilization period(the drought rate less changed,with a slight increasing in recent years)from 1991 to 2009;(4)global warming leads to increase precipitation and glacier meltwater,streamflow and lake water level,causing drought area rate declining since 1987.更多还原