2015年11月浙江省降水异常成因分析

摘要

By using NCEP/NCAR reanalysis data,ERSST.V3b sea surface temperature data from NOAA and the precipitation data of 66 observational stations since 1971 in Zhejiang province.The correlation between the statistical features of the abnormal atmospheric circulation as well as the tropical sea surface temperature and the more than normal precipitation in November over Zhejiang province were analyzed.Furthermore,the mechanism for anomalous precipitation in November,2015 was studied.Results show that the precipitation in November,2015 is due to the anomalous heavy decadal background,meanwhile,the Arctic Oscillation is positive and the intensity is abnormally stronger,the meridional circulation at mid-high latitude is weaker than normal,and the West Pacific subtropical high is enhanced and more westward than normal,leading to the extremely anomalous precipitation in November of 2015.Statistical analysis reveals that precipitation in November is mainly related to the geopotential height in wide ranges from Balkhash to Baikal and strength of the West Pacific subtropical high.Finally,El Ni(n)o is proved as a key external forcing factor influencing the precipitation of November in Zhejiang province.The Nino3.4 index in November of 2015 reaches the highest which result in the flooding over Zhejiang province.%利用NCEP/NCAR大气环流资料、NOAA ERSST.V3b海温资料以及浙江省66个台站1971年以来的降水资料,分析了浙江省11月降水偏多对应的高低层大气环流异常特征以及与热带海温异常的联系,并在此基础上对2015年11月浙江省降水异常偏多的事实进行梳理和个例诊断.结果显示,2015年11月浙江省处于降水偏多的气候背景,同时北半球北极涛动正位相异常偏强、中高纬地区经向环流偏弱,西北太平洋副热带高压强度异常偏强、位置偏西是造成降水异常偏多的主要原因;统计分析表明巴尔喀什湖地区500 hPa高度场和西太平洋副热带高压强度与浙江省11月份降水具有显著相关;厄尔尼诺是导致浙江省11月降水偏多的重要外强迫因子之一,2015年11月Ni(n)o3.4指数达历史峰值,是造成浙江省同期降水异常偏多的主要原因.