Early signatures of ozone trend reversal over the Antarctic

Abstract

We report on a detailed time series analysis of long total column ozone (TO) records based on multi-satellite observations of daily resolution. We concentrate on three geographic latitudes over and around the Antarctic area, specifically on three circles at 58.5 ∘ S, 59.5 ∘ S, and 79.5 ∘ S. Almost continuous observations are available at the two former latitudes; however, data are lacking during the polar winter periods at 79.5 ∘ S, because the measurement technique requires sunlight. The methodology is motivated by level-crossing statistics, where subsets of the records above or below particular threshold levels are evaluated. Long-term trend reversal at around the turn of the century is already detectable for low TO levels in the raw time series in the "ozone-hole" region (79.5 ∘ S). In order to overcome the apparent non-stationarities of the time series, we determined daily TO differences (ΔTO) belonging to the same geographic longitudes between the different latitudinal circles. The result is a stable, stationary behavior for small (absolute) ΔTO values in the period January-February-March without any significant detectable trends. The high absolute value ΔTO subsets (September-October-November) indicate a robust trend reversal in the middle of the 1990s. The observed trend reversal in the total column ozone time series is consistent with the temporal development of the stratospheric halogen loading. However, a close correspondence of ozone and halogen turnaround years is not expected because of the statistical uncertainties in the determination of the ozone turnaround, and the many factors contributing to ozone depletion processes.

Ozone variability in the troposphere and the stratosphere from the first 6 years of IASI observations (2008–2013)

“…In agreement with FTIR observations (e.g. Steinbrecht et al, 2006a;Vigouroux et al, 2008), a shift of the O 3 maximum from spring (March-April) to late summer (August-September) is found as one moves from high to low latitudes in the NH. In the SH, the general shape of the annual cycle, which shows a peak in October-November before the highest solar elevation (in December), results from loss mechanisms depending on the annual cycle of temperatures and other trace gases.…”

“…Overall, today there are still large differences in the value of the O 3 trends determined from independent studies and data sets (mostly from ground-based and satellite observations) in both the stratosphere and the troposphere (e.g. Oltmans et al, 1998Oltmans et al, , 2006Randel and Wu, 2007;Gardiner et al, 2008;Vigouroux et al, 2008Vigouroux et al, , 2015Jiang et al, 2008;Kyrölä et al, 2010). In order to improve on this and because O 3 has been recognised as one of the Global Climate Observing System (GCOS) Essential Climate Variables (ECVs), the scientific community has underlined the need of acquiring high-quality global, long-term and homogenised ozone profile records from satellites (Randel and Wu, 2007;Jones et al, 2009;WMO, 2007WMO, , 2011WMO, , 2014.…”

Onset of Stratospheric Ozone Recovery in the Antarctic Ozone Hole in Assimilated Daily Total Ozone Columns

“…Both records show large changes in the 1980s and early 1990s—an increase in OMD and a decrease in the average ozone column—and smaller, opposite changes after the year 2000. The identification of the year 2000 as turnaround year for Antarctic stratospheric ozone is consistent with Várai et al (). The correlation ( R 2 ) between the OMD and the amount of ODSs (EESC) is 0.71 over the full time period.…”

“…Note that the MERRA-2-based NAT volume as derived for other months is presented and discussed in Figure S2 in the supporting information. Várai et al (2015). The correlation (R 2 ) between the OMD and the amount of ODSs (EESC) is 0.71 over the full time period.…”

“…The ban on emissions of ODSs resulted in a stabilization of atmospheric concentrations of CFCs in the late 1990s and led to a subsequent gradual decline—by approximately 1–1.5% per year—of the most important CFCs ever since (Newman et al, ; WMO, ). In conjunction, the thinning of the ozone layer during springtime over Antarctica stabilized in the late 1990s as well (Várai et al, ; WMO, , ), with springtime Antarctic average total ozone columns typically reduced by 50% compared to pre‐1980 preozone hole conditions. Full recovery to these preozone hole conditions is not expected before 2050 (Newman et al, ; Chipperfield et al, ; WMO ).…”