Drastic change in dynamics as Typhoon Lekima experiences an eyewall replacement cycle  

作　　者：Fen XU X.San LIANG 

机构地区：[1]School of Atmospheric Sciences,Nanjing University of Information Science and Technology,Nanjing 210044,China. [2]School of Marine Sciences,Nanjing University of Information Science and Technology,Nanjing 210044,China

出　　处：《Frontiers of Earth Science》2022年第1期121-131,共11页地球科学前沿（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.41975064);the 2015 Jiangsu Program for Innovation Research and Entrepreneurship Groups.

摘　　要：Why does the 1909 typhoon,Lekima,become so destructive after making landfall in China?Using a newly developed mathematical apparatus,the multiscale window transform(MWT),and the MWT-based localized mutliscale energetics analysis and theory of canonical transfer,this study is intended to give a partial answer from a dynamical point of view.The ECMWF reanalysis fields are first reconstructed onto the background window,the TC-scale window,and the convection-scale window.A localized energetics analysis is then performed,which reveals to us distinctly different scenarios before and after August 8–9,2019,when an eyewall replacement cycle takes place.Before that,the energy supply in the upper layer is mainly via a strong upper layer-limited baroclinic instability;the available potential energy thus-gained is then converted into the TC-scale kinetic energy,with a portion to fuel Lekima’s upper part,another portion carried downward via pressure work flux to maintain the cyclone’s lower part.After the eyewall replacement cycle,a drastic change in dynamics occurs.First,the pressure work is greatly increased in magnitude.A positive baroclinic transfer almost spreads throughout the troposphere,and so does barotropic transfer;in other words,the whole air column is now both barotropically and baroclinically unstable.These newly occurred instabilities help compensate the increasing consumption of the TC-scale kinetic energy,and hence help counteract the dissipation of Lekima after making landfalls.

关 键 词：Typhoon Lekima multiscale window transform canonical transfer multiscale energetics barotropic/baroclinic instability 

分 类 号：P444[天文地球—大气科学及气象学]