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| Titel |
Total ozone trends and variability during 1979–2012 from merged data sets of various satellites |
| VerfasserIn |
W. Chehade, M. Weber, J. P. Burrows |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 13 ; Nr. 14, no. 13 (2014-07-11), S.7059-7074 |
| Datensatznummer |
250118880
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| Publikation (Nr.) |
 copernicus.org/acp-14-7059-2014.pdf |
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| Zusammenfassung |
The study presents a long-term statistical trend analysis of total ozone data
sets obtained from various satellites. A multi-variate linear regression was
applied to annual mean zonal mean data using various natural and
anthropogenic explanatory variables that represent dynamical and chemical
processes which modify global ozone distributions in a changing climate. The
study investigated the magnitude and zonal distribution of the different
atmospheric chemical and dynamical factors contributing to long-term total
ozone changes. The regression model included the equivalent effective
stratospheric chlorine (EESC), the 11-year solar cycle, the quasi-biennial
oscillation (QBO), stratospheric aerosol loading describing the effects from
major volcanic eruptions, the El Niño–Southern Oscillation (ENSO), the
Arctic and Antarctic oscillation (AO/AAO), and accumulated eddy heat flux
(EHF), the latter representing changes due to the Brewer–Dobson circulation.
The total ozone column data set used here comprises the Solar Backscater
Ultraviolet SBUV/SBUV-2 merged ozone data set (MOD) V8.6, the merged data set
of the Solar Backscaterr Ultraviolet, the Total Ozone Mapping Spectrometer
and the Ozone Monitoring Instrument SBUV/TOMS/OMI (1979–2012) MOD
V8.0 and the merged data set of the Global Ozone Monitoring Experiment,
the Scanning Imaging Absorption spectroMeter for Atmospheric ChartograpHY and
the Global Ozone Monitoring Experiment 2 GOME/SCIAMACHY/GOME-2 (GSG)
(1995–2012). The trend analysis was performed for twenty-six 5° wide
latitude bands from 65° S to 65° N, and the analysis
explained most of the ozone variability to within 70 to 90%. The results
show that QBO dominates the ozone variability in the tropics (±7 DU)
while at higher latitudes, the dynamical indices, AO/AAO and eddy heat flux,
have substantial influence on total ozone variations by up to ±10 DU.
The contribution from volcanic aerosols is only prominent during the major
eruption periods (El Chichón and Mt. Pinatubo), and together with the
ENSO signal, is more evident in the Northern Hemisphere. The signature of the
solar cycle covers all latitudes and contributes about 10 DU from solar
maximum to solar minimum. EESC is found to be a main contributor to the
long-term ozone decline and the trend changes after the end of the 1990s.
From the EESC fits, statistically significant upward trends after 1997 were
found in the extratropics, which points at the slowing of ozone decline and
the onset of ozone recovery. The EESC based trends are compared with the
trends obtained from the statistical piecewise linear trend (PWLT) model
(known as hockey stick) with a turnaround in 1997 to examine the differences
between both approaches. In case of the SBUV merged V8.6 data the EESC and
PWLT trends before and after 1997 are in good agreement (within 2 σ),
however, the positive post-1997 linear trends from the PWLT regression are
not significant within 2 σ.
A sensitivity study is carried out by comparing the regression results, using
SBUV/SBUV-2 MOD V8.6 merged time series (1979–2012) and a merged data set
combining SBUV/SBUV-2 (1979–June 1995) and GOME/SCIAMACHY/GOME-2 ("GSG")
WFDOAS (Weighting Function DOAS) (July 1995–2012) as well as SBUV/TOMS/OMI
MOD V8.0 (1979–2012) in the regression analysis in order to investigate the
uncertainty in the long-term trends due to different ozone data sets and data
versions. Replacing the late SBUV/SBUV-2 merged data record with GSG data
(unscaled and adjusted) leads to very similar results demonstrating the high
consistency between satellite data sets. However, the comparison of the new
SBUV/SBUV-2 MOD V8.6 with the MOD V8.0 and MOD8.6/GSG data showed somewhat
smaller sensitivities with regard to several proxies as well as the linear
EESC trends. On the other hand, the PWLT trends after 1997 show some
differences, however, within the 2 σ error bars the PWLT trends agree
with each other for all three data sets. |
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