Sammendrag
Biologically active solar Ultraviolet radiation is monitored in Kathmandu valley in Nepal (27.7 degrees N, 85.5 degrees E, 1350 m asl) using a multichannel broadband radiometer for the period of November 2004-March 2005. Result shows noontime one-hour average CIE weighted dose rate can reach up to 0.195 W m(-2) (UV index=7.8 at solar zenith angle, SZA=36.8 degrees) for a cloud free sky. Radiative transfer calculations indicate that UV index around local noon can reach as high as 14 in a clear summer sky, but will strongly depend on the content of aerosol in the atmosphere. Comparison of ground-based measurement with TOMS satellite derived data reveals an overestimation of UV indices by TOMS, within the period of measurement, on average by 31 +/- 4.5%. Modeled clear sky daily dose differed between 20 and 40% from ground-based measurement in February. Assuming constant aerosol level during the campaign, 5-25% of the variation in Ultraviolet radiation is caused by clouds alone. (C) 2006 Elsevier B.V. All rights reserved.
Vis fullstendig beskrivelse