Can Eddy Forcing be Responsible for the Spatial Structure of the Northern Hemisphere Annular Mode?  

作　　者：赵南 李艳 沈新勇 

机构地区：[1]State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences [2]Key Laboratory of Meteorological Disaster of Ministry of Education,Nanjing University of Information Science & Technology [3]Department of Atmospheric and Oceanic Science,University of Maryland,College Park

出　　处：《Acta meteorologica Sinica》2010年第5期584-592,共9页

基　　金：Supported by the National Natural Science Foundation of China under Grant Nos.40940022 and 40775033;the National Key Basic Research and Development Project of China under Grant No.2009CB421503;the Special Scientific Research Project for Public Interest of China under Grant No.GYHY200806009;the LaSW Fund of the Chinese Academy of Meteorological Sciences (2008);the Qinglan Project of Jiangsu Province of China (2009)

摘　　要：In order to study the origin of the spatial structure of the Northern Hemisphere Annular Mode （NAM）,a linear stochastic model is constructed empirically from the output of a GCM run.Optimal stochastic forcing in terms of the maximum variance contribution,which may be potentially related to the maintenance of the NAM,is investigated.Theoretical analysis on the dominant non-modal response to the stochastic forcing shows that this dominance is jointly decided by the properties of forcing and the non-modal growth （decay）.The results of computation demonstrate that the eddy forcing corresponding to the instantaneous rapid growth of the NAM,which is indicated by the instantaneous stochastic optimum,has a roughly similar but significantly different annular structure like that of the NAM.On the other hand,the eddy forcing corresponding to the stationary variance of the NAM,which is indicated by the asymptotic stochastic optimum,has a totally different structure from that of the NAM.These results,together with our general discussion on the relationship between the spatial structure of forcing and response,suggest that one should be careful when explaining the spatial structure of the NAM by that of the eddy forcing.In order to study the origin of the spatial structure of the Northern Hemisphere Annular Mode （NAM）,a linear stochastic model is constructed empirically from the output of a GCM run.Optimal stochastic forcing in terms of the maximum variance contribution,which may be potentially related to the maintenance of the NAM,is investigated.Theoretical analysis on the dominant non-modal response to the stochastic forcing shows that this dominance is jointly decided by the properties of forcing and the non-modal growth （decay）.The results of computation demonstrate that the eddy forcing corresponding to the instantaneous rapid growth of the NAM,which is indicated by the instantaneous stochastic optimum,has a roughly similar but significantly different annular structure like that of the NAM.On the other hand,the eddy forcing corresponding to the stationary variance of the NAM,which is indicated by the asymptotic stochastic optimum,has a totally different structure from that of the NAM.These results,together with our general discussion on the relationship between the spatial structure of forcing and response,suggest that one should be careful when explaining the spatial structure of the NAM by that of the eddy forcing.

关 键 词：AO/NAM eddy forcing spatial structure non-modal growth 

分 类 号：P434[天文地球—大气科学及气象学]