Accuracy of spectral UV model calculations 2. Comparison of UV calculations with measurements

Abstract

In this work, spectral UV calculations based on the discrete ordinate model by Stamnes et al. [1988] are compared with measurements from two different campaigns in Panorama (Greece) and on Jungfraujoch (Switzerland). Ozone input data were taken from Brewer or spectrophotometer measurements; spectral aerosol optical depths were measured by sunphotometers and by direct spectral irradiance measurements. The single-scattering albedo(SSA) and the reflectance were inverted using the procedure by King and Herman [1979]. The cosine error for global irradiance is taken into account and a correction is applied to the data if needed. We analyze the uncertainty interval of calculations as well as the uncertainty interval of measurements. We find deviations of the UV calculations around ± 10% or slightly more in Panorama and ± 5% to 10% at Jungfraujoch. Taking into consideration the uncertainty interval of the measurements, there is a large probability of reaching agreement between calculations and measurements. Comparisons of the UV calculations performed in this study with calculations performed with SSA and asymmetry model input parameters taken from aerosol climatology by d'Almeida and from IAMAP show that the calculated UV irradiances differ by up to 14% between model runs. Copyright 1997 by the American Geophysical Union.