基于SPI与相对湿润度指数的1961-2009年东北地区5-9月干旱趋势分析

依据东北地区1961-2009年71个气象台站月平均气温、降水资料，运用标准化降水指数（SPI）与相对湿润度指数等干旱指标分析了东北地区5-9月的干旱趋势。结果表明：1961-2009年，东北大部分地区在5-9月呈干旱化趋势，仅在黑龙江大兴安岭北部、黑龙江西南部以及黑龙江与吉林的东部交界处表现为湿润化；东北三省干湿震荡主要周期大约为22-24a，近49a发生了4次干湿交替，突变年为1976及1996年。就干旱发生范围而言，近49a东北地区干旱面积呈上升趋势，以1996年为分界线，农作物干旱受灾比在吉林增幅最大，辽宁次之，黑龙江最小，采用SPI与相对湿润度指数评价东北地区干旱较符合实际。就干旱发生频率而言，高值区主要集中在东北西部，特别是黑龙江的齐齐哈尔与大庆地区、吉林的白城地区及辽宁的朝阳地区。干旱与极端干旱的发生频率在1981-1990年较低，在2001-2009年最高，而极端干旱发生频率增加幅度明显高于一般干旱。

Drought tendency based on standardized precipitation index(SPI)and relative moisture index over Northeast China from May to September during 1961-2009

Based on the monthly mean air temperature and precipitation from 71 meteorological stations in Northeast China from 1961 to 2009,the drought tendency from May to September were analyzed using standardized precipitation index(SPI)and relative moisture index.The results indicate that the drought tendency from May to September is obvious in most of Northeast China regions except in the north of Daxing′anling region,in the southwest of Heilongjiang province and in the boundary between the east of Jinlin province and Heilongjiang province.The phenomena of drought and moisture alternations exists periodic oscillations with a cycle of 22-24 years in Northeast China.There are four drought and moisture alternations in the recent 49 years,and abrupt changes appear in 1976 and 1996.Meanwhile,drought areas in Northeast China are in an increasing trend in the recent 49 years in terms of drought ranges.Compared with the drought situation before 1996,the increasing amplitude of affected crop area for drought disaster is the largest in Jilin province after 1996,then in Liaoning province,and the smallest in Heilongjiang province.It is more realistic to use SPI and relative moisture index as the drought assessment index in Northeast China.In terms of drought frequency,the area with large values concentrates in the west of Northeast China,especially in Qiqihar and Daqing in Heilongjiang province,Baicheng in Jilin province and Chaoyang in Liaoning province.The frequency of drought and extreme drought is lower from 1981 to 1990 and higher from 2001 to 2009,and the frequency of increased amplitude of extreme drought is higher than that of the normal drought.