A comparison of two-stream DISORT and Eddington radiative transfer schemes in a real atmospheric profile

Solutions of the two-stream DISORT and Eddington radiative transfer schemes are presented with explicit forms of diffuse and direct results. In the single layer, we found that the two schemes are roughly comparable in accuracy. The Eddington scheme was slightly more accurate in the thick optical depth region, while the two-stream DISORT results were slightly better in the thin optical depth region where the solar zenith angle is less than 60∘. In multi-layer cases with the inclusion of gaseous transmission and cloud, both of the two-stream schemes were generally accurate under clear sky conditions, with a relative error of less than 1.5% for heating rate and flux. However, under cloudy conditions, cloud heating might have been underestimated by as much as 12%, which indicates that a four-stream or higher-stream scheme is necessary to obtain the accurate solar cloud absorption in climate models.