Geoscience Reference
In-Depth Information
agreement with other studies (e.g., Trepte and Hitchman
1992
; Baldwin et al.
2001
;
Choi et al.
2002
), this biennial variation was explained by the secondary meridional
circulation (SMC) of the quasi-biennial oscillation (QBO). The vertical extension of
the aerosol layer is affected by the SMC depending on the wind shear period of the
QBO in the stratosphere. In order to demonstrate this, ECMWF ERA-Interim
reanalysis data of the zonal-mean zonal wind were used.
We found that the wind speed at 10 hPa is representative for the underlying wind
shear period and we showed that
it anticorrelates with the aerosol extinction
coef
cients at 30 km altitude. Furthermore, a delayed and reduced maximum in the
aerosol extinction in 2011 was explained by two longer westerly phases during the
last four years of the time series in combination with more deeply penetrating
westerly winds of the semi-annual oscillation (SAO) that occurs in the mesosphere
and upper stratosphere.
Acknowledgments SCIAMACHY is jointly funded by Germany, the Netherlands and Belgium.
This work was in part funded by the State and the University of Bremen, the European Space
Agency (ESA), and the German Aerospace Agency (DLR). The ERA-Interim reanalysis data were
provided by ECMWF. RH is funded by the BMBF through the ROSA project (funding reference
code 01LG1212A). CvS was supported by the Ernst-Moritz-Arndt-University of Greifswald.
Thanks to Claudia Timmreck from the Max Planck Institute (MPI) Hamburg for helpful
discussions.
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