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Ann. Geophys., 24, 427-441, 2006
www.ann-geophys.net/24/427/2006/
© European Geosciences Union 2006
Daily and annual variations of erythemal ultraviolet radiation in Southwestern Spain
A. Serrano, M. Antón, M. L. Cancillo, and V. L. Mateos
Departamento de Física, Universidad de Extremadura, 06071 Badajoz, Spain
Abstract. The potential danger of ultraviolet (UV) radiation and its increasing levels
at the Earth's surface due to ozone depletion have demanded worldwide
representative measurements of UV radiation. This study presents four and one-half years
of original records of high temporal resolution ultraviolet
erythemal radiation (UVER) measured in Badajoz, Spain. Its principal aim is
to statistically characterize the UVER magnitude and temporal variations, but
also to address the interesting special cases of cloud-free and cloudy skies.
In particular, the study reports reliable values of fundamental statistical
indices, which can serve as relevant values for comparison with other studies
and model results. Moreover, the daily and annual evolution of the main
central moments of the distribution function are analyzed and interpreted in
terms of the forcing and attenuation sources.
The analysis focuses on two different temporal scales: hourly and daily
values. Integrated hourly and daily data allow for the study of daily and
annual variations of the fundamental statistical indices. All of them exhibit
high symmetry with respect to solar noon and to certain dates near summer and
winter solstices. The analysis shows the great influence of cloudiness in the
distribution of UVER values. Thus, both daily and hourly UVER data present a
slightly asymmetrical, left tailed, mesokurtic distribution for all months,
except for summer, when the lack of clouds produces a leptokurtic distribution which is skewed to the left.
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