Implementation of Turbulent Mixing over a Stratocumulus-Topped Boundary Layer and Its Impact in a GCM

作     者：Sun-Hee SHIN Kyung-Ja HA 

作者机构：Division of Earth Environmental System Pusan National University 

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：995-1004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 Ministry of Environment of Korea as "The Eco-technopia 21 Project" supported by Pusan National University under the "Post-Doc. 2008 Program" 

主　　题：stratocumulus topped boundary layer non-local diffusion scheme tropical circulation general circulation model 

摘      要：The effect of a vertical diffusion scheme over a stratocumulus topped boundary layer （STBL） was investigated using the YONU AGCM （Yonsei University Atmospheric General Circulation Model）. To consider the impact of clouds on the turbulence production, the turbulence mixing term, driven by radiative cooling at the cloud top, is implemented as an extended non-local diffusion scheme. In the model with this new scheme, the STBL parameterization significantly influences the lower atmosphere over the tropical and subtropical regions. Consideration of the turbulent mixing within the cloud layer leads to continuous stratocumulus formation. The cloud-top radiative cooling tends to favor more rapid entrainment and produces top-down turbulent mixing. This cooling develops a mixed layer without initiation of deep convection by surface fluxes. Variations in thermodynamical and dynamical features are produced by planetary boundary layer （PBL） cloud development. The simulated stratocumulus induces more mixing of heat and moisture due to the cloud forcing. Over STBL regions, the lower boundary layer becomes warmer and drier. It also weakens vertical motion and zonal trade winds in the eastern Pacific, which indicates that stratocumulus cloud cover plays a role in weakening the Walker circulation; that is, cloud cover damps the tropical circulation.