Atmos. Chem. Phys. Discuss., 13, 13495-13518, 2013
© Author(s) 2013. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Net influence of an internally-generated QBO on modelled stratospheric climate and chemistry
M. M. Hurwitz1,2, L. D. Oman2, P. A. Newman2, and I.-S. Song3
1Goddard Earth Science Technology and Research (GESTAR), Morgan State University, Baltimore, MD, USA
2NASA Goddard Space Flight Center, Greenbelt, MD, USA
3Korea Institute of Atmospheric Prediction Systems (KIAPS), Seoul, South Korea

Abstract. A Goddard Earth Observing System Chemistry–Climate Model (GEOSCCM) simulation with strong tropical non-orographic gravity wave drag (GWD) is compared to an otherwise identical simulation with near-zero tropical non-orographic GWD. The GEOSCCM generates a quasi-biennial oscillation (QBO) zonal wind signal in response to strong, quasi-realistic tropical GWD. The modelled QBO has a frequency and amplitude that closely resembles observations. In the annual mean, the modelled QBO improves the simulation of tropical zonal winds and enhances tropical and sub-tropical stratospheric variability. Also, inclusion of the QBO slows the meridional overturning circulation, resulting in a generally older stratospheric mean age-of-air. Slowing of the overturning circulation, changes in stratospheric temperature and enhanced sub-tropical mixing all affect the mean distributions of ozone, methane and nitrous oxide. Furthermore, the modelled QBO enhances polar stratospheric variability in winter. Because tropical zonal winds are easterly in the simulation without a QBO, there is a relative increase in tropical zonal winds in the simulation with a QBO. Extra-tropical differences between the simulations with and without a QBO thus reflect a bias toward the westerly phase of the QBO: a relative strengthening of the polar stratospheric jet, polar stratospheric cooling and a weak reduction in Arctic lower stratospheric ozone.

Citation: Hurwitz, M. M., Oman, L. D., Newman, P. A., and Song, I.-S.: Net influence of an internally-generated QBO on modelled stratospheric climate and chemistry, Atmos. Chem. Phys. Discuss., 13, 13495-13518, doi:10.5194/acpd-13-13495-2013, 2013.
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