UV‐B climatology in Central Spain

Abstract

AbstractBroadband ultraviolet‐B solar irradiance, 280–315 nm, at ground level in Valladolid (Spain) has been recorded for a 45‐month period, from July 2002 to March 2006.Daily maximum of hourly average irradiance values occur in July, 2.02 W m−2, and minimum, 0.3 W m−2, in December at solar noon. UV‐B daily values follow the pattern of the solar elevation angle; the total accumulated UV‐B irradiation along a mean year reaches 7.04 MJ m−2.A study of the most representative statistical characteristics of hourly average UV‐B irradiance and daily irradiation values has been carried out and the results show that the inter‐quartile range is small in winter and increases in spring and summer; maximum stability in UV‐B takes place at solar noon and around summer; it can be concluded that this maximum may be considered representative of the UV‐B irradiance values.The inter‐annual variability has been examined; the monthly‐integrated UV‐B irradiation values show a large annual cycle with a maximum in July, when the influences of the annual ozone column and summer solstice occur.The UV‐B potential and extraterrestrial irradiation has been calculated and determined in order to know the attenuation of UV‐B radiation through the atmosphere. It has been obtained that the UV‐B percentage transmitted by the atmosphere increases from winter to summer, a maximum value of 10% is obtained in July and a minimum of 4% in December. The atmospheric transparency without clouds oscillates between 10% in spring and 3% in November. Copyright © 2008 Royal Meteorological Society