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Ann. Geophys., 22, 1473-1485, 2004
www.ann-geophys.net/22/1473/2004/
© European Geosciences Union 2004
Long-term variations of the UV-B radiation over Central Europe as derived from the reconstructed UV time series
J. W. Krzyscin1, K. Eerme2, and M. Janouch3
1Institute of Geophysics, Polish Academy of Sciences, Warsaw, Poland
2Tartu Observatory, Tõravere, Tartumaa, Estonia
3Solar and Ozone Observatory, Czech Hydrometeorological Institute, Hradec Kralove, Czech Republic
Abstract. The daily doses of the erythemally weighted UV radiation are reconstructed
for three sites in Central Europe: Belsk-Poland (1966–2001), Hradec
Kralove-Czech Republic (1964–2001), and Tõravere-Estonia (1967–2001) to
discuss the UV climatology and the long-term changes of the UV-B radiation
since the mid 1960s. Various reconstruction models are examined: a
purely statistical model based on the Multivariate Adaptive Regression
Splines (MARS) methodology, and a hybrid model combining radiative transfer
model calculations with empirical estimates of the cloud effects on the UV
radiation. Modeled long-term variations of the surface UV doses appear to be
in a reasonable agreement with the observed ones. A simple quality control
procedure is proposed to check the homogeneity of the biometer and pyranometer
data. The models are verified using the results of UV observations carried
out at Belsk since 1976. MARS provides the best estimates of the UV doses,
giving a mean difference between the modeled and observed monthly means equal
to 0.6±2.5%. The basic findings are: similar climatological forcing
by clouds for all considered stations (~30% reduction in the
surface UV), long-term variations in UV monthly doses having the same temporal
pattern for all stations with extreme low monthly values (~5% below overall
mean level) at the end of the 1970s and extreme high monthly values (~5% above overall mean level) in the mid 1990s, regional peculiarities
in the cloud long-term forcing sometimes leading to extended periods with
elevated UV doses, recent stabilization of the ozone induced UV long-term
changes being a response to a trendless tendency of total ozone since the mid
1990s. In the case of the slowdown of the total ozone trend over Northern Hemisphere
mid-latitudes it seems that clouds will appear as the most important
modulator of the UV radiation both in long- and short-time scales over
next decades.
Key words. Atmospheric composition and structure
(biospheric-atmosphere interaction) – Meteorology and
atmospheric dynamics (climatology; radiative processes)
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