Royal Dutch Meteorological Institute; Ministery Of Infrastructure And The Environment

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Onset of stratospheric ozone recovery in the Antarctic ozone hole in assimilated daily total ozone columns.
by Laat (KNMI), Weele (KNMI), A (KNMI),

In this paper we evaluate the long-term changes in ozone depletion within the Antarctic ozone hole using a 37 years (1979–2015) of daily ozone mass deficits (OMDs) derived from assimilated total ozone column data. For each year an “average daily OMD” is calculated over a 60 day preferential time period (day of year 220–280). Excluding years with a reduced polar stratospheric cloud (PSC) volume (the so-called PSC-limited years), the 1979–2015 time series of spatially integrated average daily OMD correlates very well with long-term changes in equivalent effective stratospheric chlorine (EESC; R2 = 0.89). We find a corresponding statistically highly significant post-2000 decrease in OMD of −0.77 ± 0.17 megaton (trend significance of 9.8σ), with an associated post-2000 change in OMD of approximately −30%, consistent with the post-2000 change in EESC relative to 1980 EESC levels of approximately −30%. The post-2000 trend significance is robust to the choice of start year. The spatial distribution of the average daily OMD trends reveals a vortex-core region (approximately covering the region [90°W–0°–90°E/75°S–85°S]) largely unaffected by dynamics with a post-2000 trend significance of >8σ, and a vortex-edge region in which the trend is locally strongly affected by vortex dynamics though not spatially integrated over the whole vortex-edge region (trend significance >9σ). For the trend significance we do not find consistent evidence for long-term changes in wave driving, vortex mixing, preozone hole conditions, or the applied assimilation method, playing a role. Our observation/assimilation-based analysis provides robust evidence of a post-2000 statistically highly significant decrease in the average daily OMD that is consistent with the long-term decrease in ozone-depleting substances since 2000, following international emission regulations.

Bibliographic data
Laat, Weele and A, Onset of stratospheric ozone recovery in the Antarctic ozone hole in assimilated daily total ozone columns.
J. Geophys. Res., 2017, 122, doi:
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