UV‐B cloud optical properties for Canada

• Published in: International journal of climatology 2010-06, Vol.30 (8), p.1246-1255
• Main Authors: Binyamin, Jacqueline, Davies, John, McArthur, Bruce
• Format: Article
• Language: English
• Subjects: aerosols; asymmetry factor; cloud effects on radiation; delta‐Eddington‐DISORT comparisons; Earth, ocean, space; Exact sciences and technology; External geophysics; Meteorology; modelling cloud optical depth; Radiative transfer. Solar radiation; single scattering albedo; UV‐B
• ISSN: 0899-8418; 1097-0088; 1097-0088
• DOI: 10.1002/joc.1966

Cloud optical properties play a highly significant role in the amount of UV‐B irradiance reaching the ground. Broadband values of UV‐B cloud optical properties are calculated for nine Canadian stations from 26 years of data. Cloud single scattering albedo ωc and asymmetry factor gc are computed from Mie theory for two values of equivalent droplet radius; 7 µm for arctic stations and 10 µm for midlatitude and subarctic stations. Overcast cloud optical depths τc are estimated iteratively for a model cloud layer located between 2 and 3 km above the surface from hourly integrated spectral Brewer spectrophotometer measurements for snow‐free cases using either the discrete ordinate radiative transfer (DISORT) or the delta‐Eddington algorithms. Median τc values calculated by both algorithms compare to within 3%. Median values are smaller for arctic stations (9–18) and between 26 and 38 for the rest. Both mean and median values are negatively correlated with latitude. Aerosol effect on τc varies between 9 and 18% on average. Copyright © 2009 Royal Meteorological Society