Evaluation of Downward Shortwave Radiation Estimations Over Tropical Ocean Surface Based on Bayesian Model Averaging Method

Abstract

Surface downward shortwave radiation (DSR) reaching the ocean surface is critical for investigating the Earth's climate and global change issues. General circulation models (GCMs) simulations are one practical approach to obtain long-term global DSR simulations. Previous studies have reported that the GCM DSR simulations exist biases and uncertainties over ocean surface. Thus, this study used the Bayesian model averaging (BMA) method to improve tropical ocean DSR simulations by weighted averaging the 48 GCM simulations. We evaluated the estimated DSR based on the BMA method using the buoy observations from the Global Tropical Moored Buoy Array (GTMBA) from 2000 to 2005. We also compared the BMA results with single GCM simulations, the estimated DSR based on the simple model averaging (SMA) method and the Clouds and the Earth's Radiant Energy System, Energy Balanced and Filled (CERES EBAF) DSR retrievals. The spatial pattern differences of the BMA results and CERES EBAF DSR retrievals were also analyzed. When the buoy observations were used as the validation data, the validation results showed that the root mean squared errors (RMSE), correlation coefficients (R), and bias of the estimated DSR based on the BMA method are 22.51 W m-2(10.27 %), 0.66, 1.79 W m−2 (0.82 %), respectively. Moreover, the estimated DSR based on the BMA method were better than any individual GCM DSR simulations and the estimated DSR based on the SMA method.