The representation of ice cloud optical properties in climate models has long been a difficult problem. Very different ice cloud optical property parameterization schemes developed based on different assumptions of ice particle shape habits, particle size distributions, and surface roughness conditions are used in various models. However, how simulated climate variables are affected by the ice cloud optical property parameterization is unclear, especially for the global cloud radiative effect and the surface temperature.

The Innovation Team for Ocean-Land-Atmosphere Interaction and Global Effect of the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) first fills the gap to identify the diverse impacts of ice cloud optical property parameterization on global cloud radiative effects and surface temperature simulations. A total of five ice cloud optical property parameterization schemes including three based on the ice habit mixtures suitable for general ice clouds (GHM), mid-latitude synoptic ice clouds (MLC), and tropical deep convective ice clouds (TDC), and two based on single ice habits namely smooth hexagonal column (SCN) and severely roughened column aggregate (ASC), were developed under a same framework and implemented in the National Center for Atmospheric Research Community Atmospheric Model version 5. A series of atmosphere-only climate simulations were carried out for each of the five cases with different ice parameterizations. The differences in the simulated top of the atmosphere shortwave and longwave cloud radiative effects (CREs) were evaluated, and the global averaged net CRE differences among the various cases range from −1.93 to 1.03 Wm−2, which is comparable in magnitude to the radiative effect induced by doubling CO2 amount. The corresponding changes in simulated surface temperature were found to be most prominent on continental regions which amount to 1 to 2 degrees in Kelvin. The results emphasized the importance of choosing a reasonable ice cloud optical property parameterization in climate simulations, especially when the results from multiple different GCMs were intercompared.

The results obtained were accepted for publication in Scientific Reports (IF: 4.38) in June 2022, entitled “Diverse cloud radiative effects and global surface temperature simulations induced by different ice cloud optical property parameterizations”. Team member Dr. Bingqi Yi, Associate Professor of the School of Atmospheric Sciences, Sun Yat-sen University, is the first and corresponding author of the article. This study was partially supported by the research grants from the National Natural Science Foundation of China, the Natural Science Foundation of Guangdong Province, the Pearl River Talents Program of Department of Science and Technology of Guangdong Province, and the funding to the innovation teams of the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai).