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Ann. Geophys., 23, 1685-1695, 2005
www.ann-geophys.net/23/1685/2005/
© European Geosciences Union 2005
Beginning of the ozone recovery over Europe? − Analysis of the total ozone data from the ground-based observations, 1964−2004
J. W. Krzyścin, J. Jaroslawski, and B. Rajewska-Więch
Institute of Geophysics, Polish Academy of Sciences, 64 Ks. Janusza Street, 01-452 Warsaw, Poland
Abstract. The total ozone variations over Europe (~50° N) in
the period 1964–2004 are analyzed for detection of signals of ozone
recovery. The ozone deviations from the long-term monthly means (1964–1980)
for selected European stations, where the ozone observations (by the Dobson
spectrophotometers) have been carried out continuously for at least 3–4
decades, are averaged and examined by a regression model. A new method is
proposed to disclose both the ozone trend variations and date of the trend
turnaround. The regression model contains a piecewise linear trend component
and the terms describing the ozone response to forcing by "natural" changes in
the atmosphere. Standard proxies for the dynamically driven ozone variations
are used. The Multivariate Adaptive Regression Splines (MARS) methodology
and principal component analysis are used to find an optimal set of the
explanatory variables and the trend pattern. The turnaround of the ozone
trend in 1994 is suggested from the pattern of the piecewise linear trend
component. Thus, the changes in the ozone mean level are calculated over the
periods 1970–1994 and 1994–2003, for both the original time series and the time
series having "natural" variations removed. Statistical significance of
the changes are derived by bootstrapping. A first stage of recovery (according
to the definition of the International Ozone Commission), i.e. lessening of a
negative trend, is found over Europe. It seems possible that the increase in
the ozone mean level since 1994 of about 1–2% is due to superposition of
the "natural" processes. Comparison of the total ozone ground-based
network (the Dobson and Brewer spectrophotometers) and the satellite (TOMS,
version 8) data over Europe shows the small bias in the mean values for the
period 1996–2004, but the differences between the daily ozone values from
these instruments are not trendless, and this may hamper an identification of the next stage of the ozone recovery over Europe.
Keywords. Atmospheric composition and structure (Middle
atmosphere-composition and chemistry) – Meteorology and
atmospheric dynamics (Climatology, Middle atmosphere dynamics)
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