Contrasting Regional Responses of Indian Summer Monsoon Rainfall to Exhausted Spring and Concurrently Emerging Summer El Nino Events  

作　　者：E.K.KRISHNA KUMAR S.ABHILASH SANKAR SYAM P.VIJAYKUMAR K.R.SANTOSH A.V.SREENATH 

机构地区：[1]Department of Atmospheric Sciences,Cochin University of Science and Technology,Cochin 682022,India [2]Advanced Centre for Atmospheric Radar Research,Cochin University of Science and Technology,Cochin 682022,India [3]Faculty of Science and Natural Resources,Universiti Malaysia Sabah,Kota Kinabalu 88400,Malaysia

出　　处：《Advances in Atmospheric Sciences》2023年第4期697-710,共14页大气科学进展（英文版）

基　　金：funding support from the National Monsoon Mission program of the Ministry of Earth Sciences(MoES),New Delhi。

摘　　要：The inverse relationship between the warm phase of the El Nino Southern Oscillation(ENSO)and the Indian Summer Monsoon Rainfall(ISMR)is well established.Yet,some El Nino events that occur in the early months of the year(boreal spring)transform into a neutral phase before the start of summer,whereas others begin in the boreal summer and persist in a positive phase throughout the summer monsoon season.This study investigates the distinct influences of an exhausted spring El Nino(springtime)and emerging summer El Nino(summertime)on the regional variability of ISMR.The two ENSO categories were formulated based on the time of occurrence of positive SST anomalies over the Nino-3.4 region in the Pacific.The ISMR’s dynamical and thermodynamical responses to such events were investigated using standard metrics such as the Walker and Hadley circulations,vertically integrated moisture flux convergence(VIMFC),wind shear,and upper atmospheric circulation.The monsoon circulation features are remarkably different in response to the exhausted spring El Nino and emerging summer El Nino phases,which distinctly dictate regional rainfall variability.The dynamic and thermodynamic responses reveal that exhausted spring El Nino events favor excess monsoon rainfall over eastern peninsular India and deficit rainfall over the core monsoon regions of central India.In contrast,emerging summer El Nino events negatively impact the seasonal rainfall over the country,except for a few regions along the west coast and northeast India.

关 键 词：exhausted spring El Nino emerging summer El Nino Indian Summer Monsoon Hadley and Walker circulation tropical easterly jet vertical integrated moisture flux convergence 

分 类 号：P4[天文地球—大气科学及气象学]