Clear-sky surface solar radiation during the South China Sea Monsoon Experiment

Downward total solar fluxes measured at Dungsha coral island (20degrees42'N, 116degrees43'E) during the South China Sea Monsoon Experiment (May-June 1998) have been calibrated and compared with radiative transfer calculations for three clear-sky days. Model calculations use water vapor and temperature profiles from radiosonde measurements, and the aerosol optical thickness is derived from sunphotometric radiance measurements. Results show that the difference between observed and model-calculated downward surface fluxes is <3% of the daily mean. Averaged over the three clear days, the difference reduces to 1%. The averaged downward surface fluxes from observations and calculations for the three selected dates are 314 and 317 W/m(2), respectively. This result is consistent with a previous study using TOGA COARE measurements, which found good agreement between observations and model calculations. This study provides an extra piece of useful information for the modeling of radiative transfer, which helps to fill in the puzzle of the absorption of solar radiation in the atmosphere.