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Radiation budget in RegCM4: simulation results from two radiative schemes over the South West Indian Ocean

Peng Li*, Qi Li, Marc Chiacchio

*Corresponding author:

ABSTRACT: One possible way to estimate the solar resource required by the solar industry, is to use Regional Climate Models (RCMs), which provide a comprehensive and physically-based state-of-the-art description of the atmosphere and its interactions with the Earth’s surface. The first application of the RCM simulations with Regional Climate Model Version 4 (RegCM4) for radiation fluxes over the South West Indian Ocean (SWIO) is documented in this paper. The main purpose of this study is analyzing the RegCM4’s performance on radiation fluxes, especially the model’s radiative schemes presentation. This could provide the basic information for the surface solar radiation temporal-spatial variability analysis with RegCM4 over SWIO region. The ERA-Interim reanalysis data for the period 2000–2005 were used to drive RegCM4 to simulate not only the radiation budget but also associated parameters such as cloud cover, precipitation and surface temperature, over Southern Africa and the SWIO with a horizontal resolution of 50 km. The two existing available radiation schemes were tested and evaluated: (1) the default radiation scheme of the NCAR Community Climate Model Version 3 (CCM); and (2) the lately implemented Rapid Radiation Transfer Model (RRTM). To analyze the behavior of the radiation schemes and their impact on the surface climate, model outputs were validated against available satellite and reanalysis data. A comparison of the seasonal radiation budget as simulated by RegCM4-CCM and RegCM4-RRTM at the surface and at the top of the atmosphere shows good qualitative agreement. RegCM4 with the RRTM scheme generally gives better performance of the radiation budget and cloud cover over the whole domain with regard to the reference data than RegCM4 with the CCM scheme, then RRTM could be chose as the radiative scheme in the following study of surface solar radiation by RegCM4.