The Forced Secondary Circulation of the Mei-yu Front  

作　　者：Zipeng YUAN Xiaoyong ZHUGE Yuan WANG 

机构地区：[1]School of Atmospheric Sciences,and Key Laboratory of Mesoscale Severe Weather of Ministry of Education,Nanjing University,Nanjing 210023,China [2]Liaoning Provincial Meteorological Information Center,Shenyang 110160,China

出　　处：《Advances in Atmospheric Sciences》2020年第7期766-780,共15页大气科学进展（英文版）

基　　金：jointly supported by the National Key R&D Programs of China(Grant No.2018YFC1507300);the National Natural Science Foundation of China(Grant No.41505086)。

摘　　要：Using National Centers for Environmental Prediction reanalysis data for the period 28 June to 12 July during 2001 to2013,the secondary circulation(SC)associated with the mei-yu front was quantitatively diagnosed by numerically solving a primitive version of the Sawyer-Eliassen equation.Results demonstrate that a direct SC exists near the mei-yu front zone during mid-summer and the synoptic-scale geostrophic deformations are the main factors determining SC structures.About94%of the sinking strength and 61%of the ascending strength in the SC are induced by the geostrophic deformations.Other terms,such as diabatic heating,ageostrophic dynamical forcing,and frictional forcing,mainly influence the fine flow pattern of the SC.The forced SC produces a frontogenesis area tilting to the north with altitude.Further diagnosis clarifies the positive feedback involving the geostrophic shear forcing and vorticity frontogenesis in the upper-level mei-yu front zone.Furthermore,statistical results indicate that all 34 deep convection cases that occurred in the warm region of the meiyu front over the period 2004-2013 experienced high-level frontogenesis associated with along-jet cold advection.The cyclonic shear forcing"moved"the monsoon SC’s subsidence branch to the warm side of the mei-yu front and caused the subsidence branch to extend downwards to the lower troposphere,conducive to the initiation of deep convection in the warm region of the mei-yu front.

关 键 词：FORCING SUBSIDENCE ALTITUDE 

分 类 号：P426[天文地球—大气科学及气象学]