Variability of the total ozone trend over Europe for the period 1950–2004 derived from reconstructed data

Abstract

Abstract. The total ozone data over Europe are available for only few ground-based stations in the pre-satellite era disallowing examination of the spatial trend variability over the whole continent. A need of having gridded ozone data for a trend analysis and input to radiative transfer models stimulated a reconstruction of the daily ozone values since January 1950. Description of the reconstruction model and its validation were a subject of our previous paper. The data base used was built within the objectives of the COST action 726 "Long-term changes and climatology of UV radiation over Europe". Here we focus on trend analyses. The long-term variability of total ozone is discussed using results of a flexible trend model applied to the reconstructed total ozone data for the period 1950-2004. The trend pattern, which comprises both anthropogenic and "natural" component, is not a priori assumed but it comes from a smooth curve fit to the zonal monthly means and monthly grid values. The ozone long-term changes are calculated separately for cold (October-next year April) and warm (May-September) seasons. The confidence intervals for the estimated ozone changes are derived by the block bootstrapping. The statistically significant negative trends are found almost over the whole Europe only in the period 1985-1994. Negative trends up to −3% per decade appeared over small areas in earlier periods when the anthropogenic forcing on the ozone layer was weak . The statistically positive trends are found only during warm seasons 1995-2004 over Svalbard archipelago. The reduction of ozone level in 2004 relative to that before the satellite era is not dramatic, i.e., up to ∼−5% and ∼−3.5% in the cold and warm subperiod, respectively. Present ozone level is still depleted over many popular resorts in southern Europe and northern Africa. For high latitude regions the trend overturning could be inferred in last decade

Reconstruction and analysis of erythemal UV radiation time series from Hradec Králové (Czech Republic) over the past 50 years

“…The annual means of (a) TOC, (b) cloud cover, and (c) daily EUV radiation doses fitted with the locally weighted scatterplot smoothing curve (red), and the mean annual variation of (d) TOC, (e) cloud cover, and (f) daily EUV radiation doses at the Hradec Králové observatory in the individual decades of the period 1964-2013. ozone depleting substances in the stratosphere, but also to the changes of atmospheric dynamics, show a very similar development to other parts of central Europe (e.g., Trepte and Winkler, 2004;Hood and Soukharev, 2005;Harris et al, 2008). The negative trends in warm seasons after 1995, which can be linked to the changes of circulation patterns affecting the concentration of ozone depleting substances in the atmosphere, were also recorded at other parts of central Europe (Krzyscin and Borkowski, 2008;Vaníček et al, 2012;Krzyścin and Rajewska-Więch, 2015). The annual variation of TOC recorded at the Hradec Králové observatory, with its minima in autumn (October) and maxima in spring (March or April), is connected to the natural variability of TOC in Europe, which is linked to the transport of ozone from low latitudes (Zvyagintsev et al, 2015).…”

“…The trends in EUV radiation, as well as TOC and cloudiness, were studied using locally weighted scatterplot smoothing (Cleveland, 1979). The current trends in TOC were evaluated using linear regression in the period 1995-2013, which was selected for this assessment because in 1995, total ozone reached its minimum over central Europe (Krzyscin and Borkowski, 2008). The effect of SZA, TOC, cloud cover, and surface UV albedo on EUV radiation daily doses and their monthly and yearly means throughout the entire study period and the five decades was analyzed using partial correlation coefficients (r part ).…”

“…According to numerous studies, atmospheric circulation and stratospheric temperature greatly affect the intensity of global ozone losses (e.g., Orsolini and Limpasuvan, 2001;Schnadt and Dameris, 2003;Hofmann et al, 2009). In the 1970s-1990s, TOC trends in central Europe showed a decline by about 3-4 % per decade, especially in spring, while the recovery of the ozone layer has been reported since the end of the 1990s (e.g., Krzyścin et al, 1998;Krzyscin and Borkowski, 2008;Vaníček et al, 2012;De Bock et al, 2014).…”

“…The scientific interest in solar UV radiation has significantly increased since the 1980s, when it was discovered that the many adverse environmental and health effects of the solar ultraviolet (UV) radiation had been reinforced by the thinning of the ozone layer (e.g., Farman et al, 1985;Krzyscin and Borkowski, 2008). The effects of UV radiation on human skin differ according to the wavelength, so the erythema action spectrum (McKinlay and Diffey, 1987) was developed to model the susceptibility of human skin to sunburn.…”

Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium

“…Many studies agree that ozone has decreased since 1980 to the mid-1990s as a consequence of anthropogenic emissions of ozone depleting substances. This period of decrease is followed by a period of significant increase (Steinbrecht et al, 2006;Harris et al, 2008;Vigouroux et al, 2008;Krzýscin and Borkowski, 2008;Herman, 2010;Bais et al, 2011). For the period before the mid-1990s, studies report on decreasing ozone values at Brussels (Bojkov et al, 1995 andZerefos et al, 1997), Reading (Bartlett and Webb, 2000), Lerwick (Smedley et al, 2012), Arosa (Bojkov et al, 1995 andStaehelin et al, 1998), Hohenpeissenberg (Bojkov et al, 1995), Sodankylä (Glandorf et al, 2005) and Thessaloniki (Glandorf et al, 2005) (see Table 7).…”