Europe's darker atmosphere in the UV-B.
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.
Seckmeyer
Gunther
G
Institute of Meteorology and Climatology, Leibniz University Hannover, Germany.
Glandorf
Merle
M
Wichers
Cordula
C
McKenzie
Richard
R
Henriques
Diamantino
D
Carvalho
Fernanda
F
Webb
Ann
A
Siani
Anna-Maria
AM
Bais
Alkiviadis
A
Kjeldstad
Berit
B
Brogniez
Colette
C
Werle
Peter
P
Koskela
Tapani
T
Lakkala
Kaisa
K
Gröbner
Julian
J
Slaper
Harry
H
denOuter
Peter
P
Feister
Uwe
U
D001272:Atmosphere; D005060:Europe; D014466:Ultraviolet Rays