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

[摘要] The total ozone data over Europe are available for only few ground-basedstations in the pre-satellite era disallowing examination of the spatialtrend variability over the whole continent. A need of having gridded ozonedata for a trend analysis and input to radiative transfer models stimulateda reconstruction of the daily ozone values since January 1950. Descriptionof the reconstruction model and its validation were a subject of ourprevious paper. The data base used was built within the objectives of theCOST action 726 "Long-term changes and climatology of UV radiation overEurope". Here we focus on trend analyses. The long-term variability oftotal ozone is discussed using results of a flexible trend model applied tothe reconstructed total ozone data for the period 1950–2004. The trendpattern, which comprises both anthropogenic and "natural" component, isnot a priori assumed but it comes from a smooth curve fit to the zonalmonthly means and monthly grid values. The ozone long-term changes arecalculated separately for cold (October–next year April) and warm(May–September) seasons. The confidence intervals for the estimated ozonechanges are derived by the block bootstrapping. The statisticallysignificant negative trends are found almost over the whole Europe only inthe period 1985–1994. Negative trends up to −3% per decade appeared oversmall areas in earlier periods when the anthropogenic forcing on the ozonelayer was weak . The statistically positive trends are found only duringwarm seasons 1995–2004 over Svalbard archipelago. The reduction of ozonelevel in 2004 relative to that before the satellite era is not dramatic,i.e., up to ~−5% and ~−3.5% in the cold and warmsubperiod, respectively. Present ozone level is still depleted over manypopular resorts in southern Europe and northern Africa. For high latituderegions the trend overturning could be inferred in last decade (1995–2004)as the ozone depleted areas are not found there in 2004 in spite ofsubstantial ozone depletion in the period 1985–1994.

[学科分类] 大气科学