A Comparison of Observed Clear-Sky Surface Irradiance with Theoretical Computations

We used radiation data taken during the Atmospheric Radiation Measurement (ARM) Enhanced Shortwave Experiment (ARESE). We constructed the total irradiance by adding the average diffuse field irradiance measured by two shaded pyranometers and the direct beam irradiance multiplied by the cosine of the solar zenith angle. We used an empirical formula introduced by Michalsky et al. (1997) to correct the bias error of the direct beam measured by the Solar and Infrared Radiation Observation system (SIROS) pyrheliometer. We used a *2-stream model to compute irradiances at the surface. A detailed explanation of both the data and the model is found in Kato et al. (1997).