Variability of UV irradiance in Europe.
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.
Seckmeyer
Gunther
G
Institute of Meteorology and Climatology, Leibniz University of Hannover, Hannover, Germany. seckmeyer@muk.uni-hannover.de
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Darius
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Glandorf
Merle
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Henriques
Diamantino
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Johnsen
Bjorn
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Webb
Ann
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Siani
Anna-Maria
AM
Bais
Alkis
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Kjeldstad
Berit
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Brogniez
Colette
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Lenoble
Jacqueline
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Gardiner
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Kirsch
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Koskela
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Kaurola
Jussi
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Uhlmann
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Slaper
Harry
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den Outer
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Janouch
Michal
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Werle
Peter
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Gröbner
Julian
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Mayer
Bernhard
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de la Casiniere
Alain
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Simic
Stana
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Carvalho
Fernanda
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D004784:Environmental Monitoring; D005060:Europe; D012621:Seasons; D014466:Ultraviolet Rays; D014887:Weather