Abstract
Downward total solar fluxes measured at Dungsha coral island (20°42'N, 116°43'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/m2, respectively. This result is consistent with a previous study using TOGA CO ARE 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.
Highlights
INTRODUCTIONThe validity of radiation model calculations of atmospheric solar (shortwave, or SW) heating has long been an unsettled issue
The validity of radiation model calculations of atmospheric solar heating has long been an unsettled issue
The aerosol optical thickness (AOT) was retrieved from the radiances measured by the Cimel Electronique CE3 l 8-1 automatic sun-tracking photometer
Summary
The validity of radiation model calculations of atmospheric solar (shortwave, or SW) heating has long been an unsettled issue. In a study of the global radiation data sets derived from surface measurements, satellite retrievals, and climate model simulations, Arking (1996) suggested that clouds had little effect on the atmospheric solar heating. Some studies have suggested that radiation models highly underestimate the clear-sky atmospheric heating and, overestimate the surface heating (Kato et al 1997; Halthore et al 1998; Arking 1999; Pilewskie et al 2000). Results of the compari son provide us information on whether the large CRF as estimated by some investigators is caused by the uncertainty ih the model calculations of SW radiation in clear atmospheres
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