Simulating Tropical Instability Waves in the Equatorial Eastern Pacific with a Coupled General Circulation Model

作     者：陈鲜艳 Masahide KIMOTO 

作者机构：National Climate Center China Meteorological Administration Center for Climate System Research University of Tokyo 

出 版 物：《Advances in Atmospheric Sciences》 (大气科学进展（英文版）)

年 卷 期：2009年第26卷第5期

页      面：1015-1026页

核心收录：

学科分类：07[理学] 070601[理学-气象学] 0706[理学-大气科学] 0816[工学-测绘科学与技术] 0825[工学-航空宇航科学与技术] 

基　　金：supported by the Postdoctoral Fellow ship given by the Japan Society for the Promotion of Science supported by the Kyousei and Kakushin Projects of the ministry of Education, Culture,Sports, Science, and Technology of Japan, the Core Research for Evolutional Science and Technology of the Japan Science and Technology Agency the National Basic Research Program of China (Grant No. 2006CB403606) 

主　　题：tropical instability waves equatorial eastern Pacific coupled general circulation model heatflux air-sea interaction 

摘      要：Satellite observations of SSTs have revealed the existence of unstable waves in the equatorial eastern Pacific and Atlantic oceans. These waves have a 20-40-day periodicity with westward phase speeds of 0.4-0.6 m s^-1 and wavelengths of 1000-2000 km during boreal summer and fall. They are generally called tropical instability waves （TIWs）. This study investigates TIWs simulated by a high-resolution coupled atmosphere-ocean general circulation model （AOGCM）. The horizontal resolution of the model is 120 km in the atmosphere, and 30 km longitude by 20 km latitude in the ocean. Model simulations show good agreement with the observed main features associated with TIWs. The results of energetics analysis reveal that barotropic energy conversion is responsible for providing the main energy source for TIWs by extracting energy from the meridional shear of the climatological-mean equatorial currents in the mixed layer. This deeper and northward-extended wave activity appears to gain its energy through baroclinic conversion via buoyancy work, which further contributes to the asymmetric distribution of TIWs. It is estimated that the strong cooling effect induced by equatorial upwelling is partially （-30%-40%） offset by the equatorward heat flux due to TIWs in the eastern tropical Pacific during the seasons when TIWs are active. The atmospheric mixed layer just above the sea surface responds to the waves with enhanced or reduced vertical mixing. Furthermore, the changes in turbulent mixing feed back to sea surface evaporation, favoring the westward propagation of TIWs. The atmosphere to the south of the Equator also responds to TIWs in a similar way, although TIWs are much weaker south of the Equator.