title: Variability of UV irradiance in Europe.
abstract: The diurnal and annual variability of solar UV radiation in Europe is described for different latitudes, seasons and different biologic weighting functions. For the description of this variability under cloudless skies the widely used one-dimensional version of the radiative transfer model UVSPEC is used. We reconfirm that the major factor influencing the diurnal and annual variability of UV irradiance is solar elevation. While ozone is a strong absorber of UV radiation its effect is relatively constant when compared with the temporal variability of clouds. We show the significant role that clouds play in modifying the UV climate by analyzing erythemal irradiance measurements from 28 stations in Europe in summer. On average, the daily erythemal dose under cloudless skies varies between 2.2 kJ m(-2) at 70 degrees N and 5.2 kJ m(-2) at 35 degrees N, whereas these values are reduced to 1.5-4.5 kJ m(-2) if clouds are included. Thus clouds significantly reduce the monthly UV irradiation, with the smallest reductions, on average, at lower latitudes, which corresponds to the fact that it is often cloudless in the Mediterranean area in summer.
authors.affiliation: Institute of Meteorology and Climatology, Leibniz University of Hannover, Hannover, Germany. seckmeyer@muk.uni-hannover.de
authors.forename: Gunther
authors.initials: G
authors.lastname: Seckmeyer
authors.forename: Darius
authors.initials: D
authors.lastname: Pissulla
authors.forename: Merle
authors.initials: M
authors.lastname: Glandorf
authors.forename: Diamantino
authors.initials: D
authors.lastname: Henriques
authors.forename: Bjorn
authors.initials: B
authors.lastname: Johnsen
authors.forename: Ann
authors.initials: A
authors.lastname: Webb
authors.forename: Anna-Maria
authors.initials: AM
authors.lastname: Siani
authors.forename: Alkis
authors.initials: A
authors.lastname: Bais
authors.forename: Berit
authors.initials: B
authors.lastname: Kjeldstad
authors.forename: Colette
authors.initials: C
authors.lastname: Brogniez
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Lenoble
authors.forename: Brian
authors.initials: B
authors.lastname: Gardiner
authors.forename: Peter
authors.initials: P
authors.lastname: Kirsch
authors.forename: Tapani
authors.initials: T
authors.lastname: Koskela
authors.forename: Jussi
authors.initials: J
authors.lastname: Kaurola
authors.forename: Beate
authors.initials: B
authors.lastname: Uhlmann
authors.forename: Harry
authors.initials: H
authors.lastname: Slaper
authors.forename: Peter
authors.initials: P
authors.lastname: den Outer
authors.forename: Michal
authors.initials: M
authors.lastname: Janouch
authors.forename: Peter
authors.initials: P
authors.lastname: Werle
authors.forename: Julian
authors.initials: J
authors.lastname: Gröbner
authors.forename: Bernhard
authors.initials: B
authors.lastname: Mayer
authors.forename: Alain
authors.initials: A
authors.lastname: de la Casiniere
authors.forename: Stana
authors.initials: S
authors.lastname: Simic
authors.forename: Fernanda
authors.initials: F
authors.lastname: Carvalho
mesh_terms: D004784:Environmental Monitoring; D005060:Europe; D012621:Seasons; D014466:Ultraviolet Rays; D014887:Weather