FGOALS-s2 Simulation of Upper-level Jet Streams over East Asia: Mean State Bias and Synoptic-scale Transient Eddy Activity  

作　　者：宋丰飞 周天军 

机构地区：[1]State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences [2]Graduate University of the Chinese Academy of Sciences [3]Climate Change Research Center, Chinese Academy of Sciences

出　　处：《Advances in Atmospheric Sciences》2013年第3期739-753,共15页大气科学进展（英文版）

基　　金：supported by the National High Technology Research and Development Program of China(Grant No.2010AA012304);the National Program on Key Basic Research Project of China(Grant No.2010CB951904);the National Natural Science Foundation of China project(Grant No.41125017);the"Strategic Priority Research Program-Climate Change:Carbon Budget and RelatedIssues"of the Chinese Academy of Sciences(Grant No.XDA05110301)

摘　　要：Upper-level jet streams over East Asia simulated by the LASG/IAP coupled climate system model FGOALS-s2 were assessed, and the mean state bias explained in terms of synoptic-scale transient eddy activ- ity （STEA）. The results showed that the spatial distribution of the seasonal mean jet stream was reproduced well by the model, except that following a weaker meridional temperature gradient （MTG）, the intensity of the jet stream was weaker than in National Centers for Environment Prediction （NCEP）/Department of Energy Atmospheric Model Inter-comparison Project II reanalysis data （NCEP2）. Based on daily mean data, the jet core number was counted to identify the geographical border between the East Asian Sub- tropical Jet （EASJ） and the East Asian Polar-front Jet （EAPJ）. The border is located over the Tibetan Plateau according to NCEP2 data, but was not evident in FGOALS-s2 simulations. The seasonal cycles of the jet streams were found to be reasonably reproduced, except that they shifted northward relative to reanalysis data in boreal summer owing to the northward shift of negative MTGs. To identify the reasons for mean state bias, the dynamical and thermal forcings of STEA on mean flow were examined with a focus on boreal winter. The dynamical and thermal forcings were estimated by extended Eliassen-Palm flux （E） and transient heat flux, respectively. The results showed that the failure to reproduce the tripolar-pattern of the divergence of E over the jet regions led to an unsuccessful separation of the EASJ and EAPJ, while dynamical forcing contributed less to the weaker EASJ. In contrast, the weaker transient heat flux partly explained the weaker EASJ over the ocean.Upper-level jet streams over East Asia simulated by the LASG/IAP coupled climate system model FGOALS-s2 were assessed, and the mean state bias explained in terms of synoptic-scale transient eddy activ- ity （STEA）. The results showed that the spatial distribution of the seasonal mean jet stream was reproduced well by the model, except that following a weaker meridional temperature gradient （MTG）, the intensity of the jet stream was weaker than in National Centers for Environment Prediction （NCEP）/Department of Energy Atmospheric Model Inter-comparison Project II reanalysis data （NCEP2）. Based on daily mean data, the jet core number was counted to identify the geographical border between the East Asian Sub- tropical Jet （EASJ） and the East Asian Polar-front Jet （EAPJ）. The border is located over the Tibetan Plateau according to NCEP2 data, but was not evident in FGOALS-s2 simulations. The seasonal cycles of the jet streams were found to be reasonably reproduced, except that they shifted northward relative to reanalysis data in boreal summer owing to the northward shift of negative MTGs. To identify the reasons for mean state bias, the dynamical and thermal forcings of STEA on mean flow were examined with a focus on boreal winter. The dynamical and thermal forcings were estimated by extended Eliassen-Palm flux （E） and transient heat flux, respectively. The results showed that the failure to reproduce the tripolar-pattern of the divergence of E over the jet regions led to an unsuccessful separation of the EASJ and EAPJ, while dynamical forcing contributed less to the weaker EASJ. In contrast, the weaker transient heat flux partly explained the weaker EASJ over the ocean.

关 键 词：FGOALS-s2 jet stream synoptic-scale transient eddy activity meridional temperature gradi-ent extended Eliaseen-Palm flux transient heat flux 

分 类 号：P434[天文地球—大气科学及气象学]