COMPARISON OF GREEN AND LOWTRAN RADIATION SCHEMES WITH A DISCRETE ORDINATE METHOD UV MODEL

Using the same input parameters for the calculations, the Green and Lo wtran codes for calculating UV irradiances were compared to the discre te ordinate method (DOM) model by Stamnes et al., which was used as a reference, The comparisons were performed at 305 and 380 nm for differ ent ozone concentrations, aerosol optical depths and aerosol absorptio n characteristics. No obvious dependencies on optical depth, single sc attering albedo or column ozone were found for the ratio of the Green and the Lowtran code to the DOM model, At 380 nm the Green model agree s with DOM within 10%, whereas the Lowtran code shows discrepancies of +/-25%. At 305 nm the Green model shows 10% higher values than the DO M model at low zenith angles and up to 80% lower values for zenith ang les between 60 and 80 degrees, The Lowtran code shows 60% higher value s than DOM at small zenith angles and 60% lower values at large zenith angles, When the spectra from each model were weighted with the eryth emal action spectrum the Green model overestimated the DONI results by less than 10% for zenith angles less than 50 degrees. Discrepancies b etween DOM and Lowtran models exceeded 10% except for a small range of zenith angles.