A Quantitative Method of Detecting Transient Rossby Wave Phase Speed:No Evidence of Slowing Down with Global Warming  

作　　者：Yashu WU Jianhua LU 

机构地区：[1]School of Atmospheric Sciences,Sun Yat-Sen University and Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519082,China [2]State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG),Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing100029,China [3]Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies,Sun Yat-sen University,Guangzhou 510275,China

出　　处：《Advances in Atmospheric Sciences》2023年第2期251-261,共11页大气科学进展（英文版）

基　　金：support from National Natural Science Foundation of China(Grant Nos.42175070,41875130);Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies(Grant No.2020B1212060025).

摘　　要：Based on the Complex Empirical Orthogonal Functions(CEOFs)of bandpass-filtered daily streamfunction fields,a quantitative method of detecting transient(synoptic)Rossby wave phase speed(RWPhS)is presented.The transient RWPhS can be objectively calculated by the distance between a high(or low)center in the real part of a CEOF mode and its counterpart in the imaginary part of the same CEOF mode divided by the time span between two adjacent peaks(or bottoms)of two principal component curves for the real and imaginary parts of that CEOF mode.The new detection method may partly reveal the spatiotemporal heterogeneity of Rossby wave prorogation.Although the mean westerly jet at 200 hPa doubles the speed of its counterpart at 500 hPa,the estimated RWPhS at both levels are around 1000 km d^(–1)and quantitatively consistent with the quasigeostrophic-theory-based RWPhS,confirming that the meridional potential vorticity gradient induced by the barotropic and baroclinic shears of mean flow,together with theβeffect,play an essential role in Rossby wave propagation.Both observations over the past four decades and a 150-year historical simulation suggest no evidence for slowing wintertime transient Rossby waves in the Northern Hemisphere,but possible regional changes are not excluded.We emphasize that not only the mean flow speed,but also the barotropic and baroclinic shears of the mean flow,and their associated contributions to the meridional potential vorticity(PV)gradient,should be considered in investigating the possible change of Rossby waves with global warming.

关 键 词：Rossby waves phase speed quasigeostrophic potential vorticity 

分 类 号：P467[天文地球—大气科学及气象学]