The Seasonal Prediction of the Exceptional Yangtze River Rainfall in Summer 2020  

作　　者：Chaofan LI Riyu LU Nick DUNSTONE Adam ASCAIFE Philip EBETT Fei ZHENG 

机构地区：[1]Center for Monsoon System Research,Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China [2]State Key Laboratory of Numerical Modelling for Atmospheric Sciences and Geophysical Fluid Dynamics,Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China [3]University of the Chinese Academy of Sciences,Beijing 100029,China [4]Met Office Hadley Centre,FitzRoy Road,Exeter EX13PB,UK [5]College of Engineering,Mathematics and Physical Sciences,University of Exeter,Exeter,Devon EX44QF,UK [6]International Center for Climate and Environment Science,Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China

出　　处：《Advances in Atmospheric Sciences》2021年第12期2055-2066,共12页大气科学进展（英文版）

基　　金：This work was supported by the National Key Research and Development Program of China(Grant No.2018YFC1506005);the National Natural Science Foundation of China(Grant Nos.41721004 and 41775083);This work and its contributors were also supported by the UK-China Research and Innovation Partnership Fund through the Met Office Climate Science for Service Partnership(CSSP)China as part of the Newton Fund.

摘　　要：During June and July of 2020,the Yangtze River basin suffered from extreme mei-yu rainfall and catastrophic flooding.This study explores the seasonal predictability and associated dynamical causes for this extreme Yangtze River rainfall event,based on forecasts from the Met Office GloSea5 operational forecast system.The forecasts successfully predicted above-average rainfall over the Yangtze River basin,which arose from the successful reproduction of the anomalous western North Pacific subtropical high(WNPSH).Our results indicate that both the Indian Ocean warm sea surface temperature(SST)and local WNP SST gradient were responsible for the westward extension of the WNPSH,and the forecasts captured these tropical signals well.We explore extratropical drivers but find a large model spread among the forecast members regarding the meridional displacements of the East Asian mid-latitude westerly jet(EAJ).The forecast members with an evident southward displacement of the EAJ favored more extreme Yangtze River rainfall.However,the forecast Yangtze River rainfall anomaly was weaker compared to that was observed and no member showed such strong rainfall.In observations,the EAJ displayed an evident acceleration in summer 2020,which could lead to a significant wind convergence in the lower troposphere around the Yangtze River basin,and favor more mei-yu rainfall.The model forecast failed to satisfactorily reproduce these processes.This difference implies that the observed enhancement of the EAJ intensity gave a large boost to the Yangtze River rainfall,hindering a better forecast of the intensity of the event and disaster mitigation.

关 键 词：seasonal forecast Yangtze River rainfall western North Pacific subtropical high westerly jet 

分 类 号：P426.62[天文地球—大气科学及气象学]