洞庭湖流域近58年季节性干旱时空分布及大气环流分析

利用洞庭湖流域1960～2017年103个气象站点逐月降水数据、NCEP/NCAR再分析数据以及Z指数,对洞庭湖流域近58年来季节性干旱的时空变化和不同干旱范围等级的大气环流形势进行分析,以加强对季节性干旱的认识。结果表明:近58年洞庭湖流域Z指数存在显著的年际和年代际变化特征,表现为20世纪60年代偏旱,70与80年代干旱呈现出显著的年际旱涝转换,90年代较湿润,进入21世纪出现年代际旱涝转换。春、夏和冬季干旱多发生在1990年之前,且流域的季节性干旱在不同的年代际存在不同的空间分布特征。流域各站点多年平均干旱频率基本在10%～30%之间。从同期大气环流形势来看,EU型遥相关波列对流域各季节干旱均有重要影响,EAP型与Silk Road型遥相关在夏、秋季节对副高强度与位置有重要影响。干旱事件在春、冬季主要受制于北方冷空气的强弱,夏(秋)季在副热带高压偏弱(强)偏北时易发生较大面积干旱。

Analysis on Spatial-temporal Distribution and Atmospheric Circulation ofSeasonal Droughts in the Dongting Lake Basin in Recent 58 Years

Abstract：Based on the monthly precipitation data of 103 meteorological stations from 1960 to 2017 in the Dongting Lake Basin, the monthly mean reanalysis data from NCEP/NCAR and Z-Index, we analyzed spatial-temporal variation characteristics of seasonal drought in recent 58 years in the Dongting Lake Basin and displayed the features of synchronous atmospheric circulation with different range levels of drought, in order to enhance the understanding of seasonal drought. The results shows that, the Z-index in the Dongting Lake basin exhibits significant inter-annual and inter-decadal variation characteristics in the past 58 years. To be more specific, the Z-index is characterized by relatively severe drought in 1960s, obvious inter-annual transitions of drought and flood in 1970s and 1980s, wet phase in 1990s, and an inter-decadal transition of drought and flood after entering 21st century. The droughts in spring, summer and winter occurred mostly before 1990, and the seasonal drought in the basin exhibits different spatial distribution characteristics in different ages. The multi-annual average drought frequency of each station in the basin intermediates between 10% and 30% nearly. Through the features of synchronous atmospheric circulation, the Eurasian pattern teleconnection wave train exerts an important effect on the drought in every season in the basin. The East Asia/Pacific pattern and the Silk Road pattern teleconnection have noticeable effect on the intensity and position of the western pacific subtropical high in summer and autumn. The drought are mainly affected by the cold airflow from the north in spring and winter, and the drought with larger area is more likely to occur in the summer(autumn) when the subtropical high is weak(strong) and northerly.