The impact of radiation parameterization schemes on the regional climate simulations over the CORDEX-EA domain

Abstract

This study evaluates the impact of radiation schemes on the regional climate simulations with the WRF (Weather Research and Forecasting) model over the CORDEX-EA (Coordinated Regional Climate Downscaling Experiment-East Asia) domain during 1989–2008. The model is driven by the ERA-Interim reanalysis at a horizontal resolution of 50 km, and the two radiation schemes of CAM (Community Atmosphere Model) and RRTMG (Rapid Radiative Transfer Model for Global Climate Models) are applied. The mean and extreme temperature is generally underestimated by the model over most areas, with the greatest bias reaching 8 °C over the Tibetan Plateau, which can be explained by the underestimation of the long wave radiation. The RRTMG scheme reduces the underestimation of long wave radiation by about 30 W/m2 in most regions, and thus reduces the root mean square error of annual mean temperature over the east Asia domain by about 0.77 °C. The simulations of precipitation show little dependence on the radiation schemes, with slight superiority in the CAM-driven experiment. The model's performance of producing the interannual variation of the temperature can be partly attributed to that of the long wave radiation, and the CAM scheme works slightly better in producing the interannual feature of both temperature and precipitation. The seasonal cycles of both temperature and precipitation are reasonably produced by the model. The cold bias of temperature is found to mainly occur in the cold months through the year, which is probably associated with the greater underestimation of long wave radiation flux in the cold months.