Improving Representation of Tropical Cloud Overlap in GCMs Based on Cloud-Resolving Model Data  

作　　者：Xianwen JING Hua ZHANG Masaki SATOH Shuyun ZHAO 

机构地区：[1]Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing 210044, China [2]State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China [3]Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa 2778564, Japan [4]Laboratory for Climate Studies, National Climate Center, China Meteorological Administration, Beijing 100081, China

出　　处：《Journal of Meteorological Research》2018年第2期233-245,共13页气象学报（英文版）

基　　金：Supported by the National Key Research and Development Program of China(2017YFA0603502);(Key)National Natural Science Foundation of China(91644211 and 41375080);China Meteorological Administration Special Public Welfare Research Fund(GYHY201406023)

摘　　要：The decorrelation length（Lcf） has been widely used to describe the behavior of vertical overlap of clouds in general circulation models（GCMs）; however, it has been a challenge to associate Lcf with the large-scale meteorological conditions during cloud evolution. This study explored the relationship between Lcf and the strength of atmospheric convection in the tropics based on output from a global cloud-resolving model. Lcf tends to increase with vertical velocity in the mid-troposphere（w500） at locations of ascent, but shows little or no dependency on w500 at locations of descent. A representation of Lcf as a function of vertical velocity is obtained, with a linear regression in ascending regions and a constant value in descending regions. This simple and dynamic-related representation of Lcf leads to a significant improvement in simulation of both cloud cover and radiation fields compared with traditional overlap treatments. This work presents a physically justifiable approach to depicting cloud overlap in the tropics in GCMs.The decorrelation length（Lcf） has been widely used to describe the behavior of vertical overlap of clouds in general circulation models（GCMs）; however, it has been a challenge to associate Lcf with the large-scale meteorological conditions during cloud evolution. This study explored the relationship between Lcf and the strength of atmospheric convection in the tropics based on output from a global cloud-resolving model. Lcf tends to increase with vertical velocity in the mid-troposphere（w500） at locations of ascent, but shows little or no dependency on w500 at locations of descent. A representation of Lcf as a function of vertical velocity is obtained, with a linear regression in ascending regions and a constant value in descending regions. This simple and dynamic-related representation of Lcf leads to a significant improvement in simulation of both cloud cover and radiation fields compared with traditional overlap treatments. This work presents a physically justifiable approach to depicting cloud overlap in the tropics in GCMs.

关 键 词：cloud overlap decorrelation length cloud-resolving model Nonhydrostatic Icosahedral Atmospheric Model（NICAM） 

分 类 号：P426.5[天文地球—大气科学及气象学] P45