洞庭湖流域近54 a来冬季降水及其异常环流特征分析

基于洞庭湖流域96个气象站点1961~2015年逐月降水数据和美国NCEP/NCAR再分析数据,对洞庭湖流域近54 a来冬季降水的时空变化特征和典型冬涝、冬旱年的大气环流及水汽输送形势进行分析,并讨论逐年冬季降水与同期欧亚环流指数(EUCI)、可降水量和水汽通量散度的关系。结果表明:近54 a,流域冬季降水存在明显的年际和年代际变化特征,具体表现为20世纪60年代和70年代降水偏少,80年代降水开始增多,其后期至90年代中后期降水偏多明显,进入21世纪以来降水又呈波动减少的趋势。此外,流域冬季平均降水量和冬季降水标准差均呈现由南向北、由东向西递减的空间分布特征。从大气环流和水汽输送形势来看,典型冬涝年和冬旱年的空间分布大致相反,表明流域冬季异常降水是与大尺度环流形势的异常密切关联的。计算发现,逐年冬季可降水量、水汽通量散度和欧亚环流指数与流域冬季降水均具有较好的关系,相关系数分别达到0.43、-0.68、-0.53,通过0.01的信度检验。

CHARACTERISTICS OF WINTER PRECIPITATION AND CIRCULATION FOR PRECIPITATION ANOMALIES IN DONGTING LAKE BASIN DURING 1961-2014

Based on the monthly precipitation data of 96 meteorological stations from 1961 to 2015 in the Dongting Lake Basin and monthly mean reanalysis dataset from NCEP/NCAR,we analyzed spatial-temporal variation characteristics of winter precipitation in recent 54 years in Dongting Lake Basin and the feature of atmospheric circulation and water vapor transport during typical winter flood/drought years.We also discussed the relationships between annual winter precipitation and synchronized Eurasian Circulation Index (EUCI),precipitable water,water vapor flux divergence.The results showed that,winter precipitation in the Dongting Lake Basin exhibits remarkable inter-annual and inter-decadal variation characteristics in the past 54 years,for concrete manifestation,there were less rainfall in 1960s and 1970s,more rainfall from 1980s to late 1990s,winter precipitation exhibits fluctuant decreasing trend after entering 21 century.In addition,winter mean precipitation and standard deviation of winter precipitation in the Dongting Lake Basin both exhibit decreasing spatial distribution characteristics from south to north,east to west.In terms of the feature of atmospheric circulation and water vapor transport,spatial distribution are roughly opposite during typical winter flood years and typical winter drought years.the results showed that anomalous winter precipitation in the Dongting Lake Basin are closely associated with large-scale circulation situation anomaly.By respectively calculating correlation coefficient between annual precipitable water,water vapor flux divergence,Eurasian Circulation Index and winter precipitation in the Dongting Lake Basin,we found that there are fairly good relationships between them,correlation coefficient are respectively 0.43,-0.68,-0.53,and all are significant above the 0.01 significance level.