中国南方冬雨与El Nio事件相关关系的年代际差异及其成因

Interdecadal differences in correlations between the winter precipitation over the southern China and El Nio events and their causes

利用1961—2016年中国160站逐月降水资料和NCEP/NCAR再分析资料,采用统计学方法分析了中国南方冬雨与El Nio事件相关关系的年代际差异及其成因。结果表明:1) 1961—2016年南方冬雨年际变化显著,且降水量呈现阶段性变化,1961—1988年为少雨期,1989—2016年为多雨期。2) El Nio事件与南方冬雨之间的相关关系存在年代际差异。1961—1988年El Nio事件冬季,500 hPa上中国东部地区位势高度距平的经向差异很小,不利于冷空气向南推进,850 hPa上中国南方南风距平偏小,来自孟加拉湾和南海的水汽较难向中国南方地区输送,且中国南方地区受下沉运动异常影响,对流发展受抑制,故南方冬雨偏少; 1989—2016年El Nio事件冬季,500 h Pa上中国东部地区位势高度距平的经向梯度较大,有利于冷空气向南推进,850 hPa上南海北部到中国东部出现异常的西南风,有利于孟加拉湾和南海的暖湿气流向中国南方地区输送,且中国南方地区受上升运动异常控制,有利于对流发展,故南方冬雨偏多。

Based on the monthly precipitation data from 160 stations in China and the NCEP/NCAR reanalysis data from 1961 to 2016,the interdecadal differences in correlations between the winter precipitation over the southern China and El Nino events and their causes are studied using statistical analysis methods.Results show that:1)The winter precipitation over the southern China has obvious interannual variations from 1961 to 2016 and presents the characteristics of periodic change with a dry period from 1961 to 1988 and a rainy period from 1989 to 2016.2)There are interdecadal differences in correlations between the winter precipitation over the southern China and El Nino events during the two periods.In winter of El Nino events from 1961 to 1988,the meridional gradient of geopotential height anomaly at 500 hPa over the eastern China is small,which is not conducive to the southward intrusion of the cold air.The south wind velocity anomaly at 850 hPa over the southern China is very small,it is difficult for the water vapor from the Bay of Bengal and the South China Sea to transport to the southern China,and the southern China is controlled by anomalous downward movement,which is not beneficial to convection development.Therefore,the winter precipitation is less.In winter of El Nino events from 1989 to 2016,the meridional gradient of geopotential height anomaly at 500 hPa over the eastern China is greater,which is conducive to the southward intrusion of the cold air.The southwest wind anomaly at 850 hPa from the northern part of the South China Sea to the eastern China helps transport the warm and wet air from the Bay of Bengal and the South China Sea to the southern China.The southern China is controlled by anomalous upward movement,which is beneficial to convection development.As a result,the winter precipitation is more.