title: Europe's darker atmosphere in the UV-B.
abstract: Irradiation in the ultraviolet wavelength range is found to be up to 50% lower in the European summer compared to sites with comparable latitudes in New Zealand. We have developed a method to quantitatively attribute the causes for such differences between sites by analysis of spectra. We conclude that these large differences are caused mainly by differences in total ozone, cloudiness, aerosol loading and Sun-Earth separation. The relative contribution of clouds varies from year to year and it is site dependent. Averaged over several years we find a strong latitudinal gradient of the cloud impact within Europe, with much less cloud attenuation in southern Europe. Due to the differences in total ozone and aerosol loading, the UV-B levels are generally lower in Europe compared to New Zealand. It is likely that inter-hemispheric differences will change in coming decades due to a combination of changes in ozone concentrations, air pollution and cloudiness as a result of climate change. However, since the future evolution of these major parameters is highly uncertain, the magnitude and even the sign of such changes are not known yet.
authors.affiliation: Institute of Meteorology and Climatology, Leibniz University Hannover, Germany.
authors.forename: Gunther
authors.initials: G
authors.lastname: Seckmeyer
authors.forename: Merle
authors.initials: M
authors.lastname: Glandorf
authors.forename: Cordula
authors.initials: C
authors.lastname: Wichers
authors.forename: Richard
authors.initials: R
authors.lastname: McKenzie
authors.forename: Diamantino
authors.initials: D
authors.lastname: Henriques
authors.forename: Fernanda
authors.initials: F
authors.lastname: Carvalho
authors.forename: Ann
authors.initials: A
authors.lastname: Webb
authors.forename: Anna-Maria
authors.initials: AM
authors.lastname: Siani
authors.forename: Alkiviadis
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: Peter
authors.initials: P
authors.lastname: Werle
authors.forename: Tapani
authors.initials: T
authors.lastname: Koskela
authors.forename: Kaisa
authors.initials: K
authors.lastname: Lakkala
authors.forename: Julian
authors.initials: J
authors.lastname: Gröbner
authors.forename: Harry
authors.initials: H
authors.lastname: Slaper
authors.forename: Peter
authors.initials: P
authors.lastname: denOuter
authors.forename: Uwe
authors.initials: U
authors.lastname: Feister
mesh_terms: D001272:Atmosphere; D005060:Europe; D014466:Ultraviolet Rays