Publication Date:
2017-04-04
Description:
We report results from a multiple linear regression
analysis of long-term total ozone observations (1979 to
2000, by TOMS/SBUV), of temperature reanalyses (1958
to 2000, NCEP), and of two chemistry-climate model simulations
(1960 to 1999, by ECHAM4.L39(DLR)/CHEM
(=E39/C), and MAECHAM4-CHEM). The model runs are
transient experiments, where observed sea surface temperatures,
increasing source gas concentrations (CO2, CFCs,
CH4, N2O, NOx), 11-year solar cycle, volcanic aerosols
and the quasi-biennial oscillation (QBO) are all accounted
for. MAECHAM4-CHEM covers the atmosphere from the
surface up to 0.01 hPa ( 80 km). For a proper representation
of middle atmosphere (MA) dynamics, it includes
a parametrization for momentum deposition by dissipating
gravity wave spectra. E39/C, on the other hand, has its top
layer centered at 10 hPa ( 30 km). It is targeted on processes
near the tropopause, and has more levels in this region.
Despite some problems, both models generally reproduce
the observed amplitudes and much of the observed lowlatitude
patterns of the various modes of interannual variability
in total ozone and lower stratospheric temperature. In
most aspects MAECHAM4-CHEM performs slightly better
than E39/C. MAECHAM4-CHEM overestimates the longterm
decline of total ozone, whereas E39/C underestimates
the decline over Antarctica and at northern mid-latitudes.
The true long-term decline in winter and spring above the
Correspondence to: W. Steinbrecht
(wolfgang.steinbrecht@dwd.de)
Arctic may be underestimated by a lack of TOMS/SBUV
observations in winter, particularly in the cold 1990s. Main
contributions to the observed interannual variations of total
ozone and lower stratospheric temperature at 50 hPa come
from a linear trend (up to −10 DU/decade at high northern
latitudes, up to −40 DU/decade at high southern latitudes,
and around −0.7 K/decade over much of the globe), from
the intensity of the polar vortices (more than 40 DU, or 8 K
peak to peak), the QBO (up to 20 DU, or 2 K peak to peak),
and from tropospheric weather (up to 20 DU, or 2 K peak
to peak). Smaller variations are related to the 11-year solar
cycle (generally less than 15 DU, or 1 K), or to ENSO (up
to 10 DU, or 1 K). These observed variations are replicated
well in the simulations. Volcanic eruptions have resulted in
sporadic changes (up to −30 DU, or +3 K). At low latitudes,
patterns are zonally symmetric. At higher latitudes, however,
strong, zonally non-symmetric signals are found close
to the Aleutian Islands or south of Australia. Such asymmetric
features appear in the model runs as well, but often
at different longitudes than in the observations. The results
point to a key role of the zonally asymmetric Aleutian (or
Australian) stratospheric anti-cyclones for interannual variations
at high-latitudes, and for coupling between polar vortex
strength, QBO, 11-year solar cycle and ENSO.
Description:
Published
Description:
349–374
Description:
open
Keywords:
temperature
;
simulations
;
01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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