热带北太平洋海温异常对2018年华南前汛期降水负异常事件的影响

Influence of SST anomalies in the tropical North Pacific on negative precipitation anomalies in South China' s first rainy season in 2018

本文利用1979—2018年中国地面气象台站1767个站点降水资料、HadISST海温数据及NCEP/NCAR再分析资料,滤除同期ENSO影响后,分析了2018年华南前汛期降水负异常与热带北太平洋海温异常之间的联系。研究结果显示,2018年华南前汛期降水负异常事件和热带北太平洋(Tropical Northern Pacific,TNP)海温偏暖有关。热带北太平洋海温正异常,通过Mastuno-Gill响应引起西北太平洋气旋式环流异常,中国南海东风异常,减弱了南海夏季风,华南至中国南海地区对流层低层存在异常反气旋环流。水汽存在由中纬度北太平洋经黑潮海区-华南地区-中国南海-菲律宾群岛向热带太平洋的异常输送,且华南地区为水汽的异常辐散区域。另一方面,TNP区域暖海温异常引起了该区域低层异常辐合、高层异常辐散、异常上升运动,使得华南地区高层异常辐合、低层异常辐散、异常下沉运动。这样的环流配置对华南地区降水的产生有不利影响,引起了2018年华南前汛期降水异常偏少。2018年TNP区域暖海温异常引起华南前汛期降水负异常的物理机制还在ECHAM5模式30个成员集合平均的试验结果中得以验证。

In 2018,the precipitation in the first rainy season in South China(Guangdong Province and Guangxi Zhuang Autonomous Region)is abnormally low,with the regional average total precipitation of 410.9 mm,which is about 40%less than the average climate.The results of this study show that the precipitation negative anomaly in the first rainy season in South China in 2018 is related to the warm sea temperature in the tropical northern Pacific(TNP).The SST positive anomaly in the tropical North Pacific results in the cyclonic circulation anomaly in the Northwest Pacific and the east wind anomaly in the South China Sea through the Mastuno-Gill response,which weakens the South China Sea summer monsoon.Abnormal anticyclonic circulation exists in the lower troposphere from South China to South China Sea.There is an abnormal transport of water vapor from the mid-latitude North Pacific Ocean to the tropical Pacific Ocean via the Kuroshio Sea Area,the South China Sea,and the Philippine Islands,and South China is an abnormal divergence region of water vapor.On the other hand,the warm sea temperature anomaly in the TNP region causes abnormal convergence in the lower layer,abnormal divergence in the upper layer,and abnormal upward movement in the region,leading to abnormal convergence in the upper layer,abnormal divergence in the lower layer,and abnormal subsidence movement in South China.This circulation arrangement is not conducive to the production of precipitation in South China,resulting in unusually little precipitation in South China's first rainy season in 2018.The physical mechanism of the TNP regional warm sea temperature anomaly causing the negative precipitation anomaly in South China's first rainy season in 2018 is also verified by the average test results of 30 member sets of the ECHAM5 model.