基于SPEI指数的东北春旱频率变化及突变成因分析

Analysis of frequency variation and causes of mutation change about spring drought over Northeast region of China

选取中国气象数据网1961~2015年东北地区66个地面气象站逐日降水和气温资料以及美国国家环境预报中心(NCEP/NCAR)的位势高度、比湿、水平风速和垂直风速再分析日资料,计算东北地区近55年来春季干旱的标准化降水蒸散指数(Standardized Precipatation Evapotranspiration Index,SPEI),利用Cressman客观分析法、Mann-kendall法、巴特沃斯滤波法以及合成分析法分析东北春旱年大气环流与运动特征。结果表明,东北地区春旱在80年代初发生突变。以1980年为界,将近55年大致分为Ⅰ时段(1961~1980年)、Ⅱ时段(1981~2015年)两个时段,并挑出两个时段的典型春旱年。分析得出:Ⅰ时段,旱情东重西轻,春旱频率较高;Ⅱ时段,旱情西重东轻,春旱频率相对较低,Ⅰ时段旱情比Ⅱ时段重。进一步研究得出,相比Ⅰ时段,Ⅱ时段的反气旋强度弱且水汽通量辐散小,使得东北春旱在1980年前后发生转变。除此之外,纬向风切变分布不均可能是东北东部和西部春旱差异的重要成因。

Based on the daily precipitation and temperature datasets of 66 meteorological stations in Northeast region of China from Meteorological Data Network and the NCEP/NCAR daily geopotential height,specific humidity,horizontal wind speed and vertical wind speed reanalysis datasets during 1961 ~ 2015,the standardized precipitation evapotranspiration indexes are calculated. The atmospheric circulation and motion characteristics are analyzed by u-sing Cressman objective analysis method,Mann-Kendall method,Butterworth filtering method and synthetic analysis method. The results show that the abrupt change of spring drought in Northeast region of China occured in early1980 s. The 55 years after 1961 are divided into two periods（ First period： 1961 ~ 1980. Second period： 1981 ~2015）,and the typical drought years are selected respectively. The frequency of spring drought is higher and the drought in the east is greater than the west of Northeast region in the first period,but the circumstance is opposite in the second period. Further study showed that,compared to the first period,the anti cyclone intensity is weaker and the water vapor flux divergence is smaller in the second period,which leaded to the abrupt change of spring drought in Northeast region of China around 1980 s. In addition,the uneven distribution of zonal wind shear may be important causes of difference between easten and western spring drought in Northeast region of China.