Atmos. Chem. Phys. Discuss., 10, 24853-24917, 2010
www.atmos-chem-phys-discuss.net/10/24853/2010/
doi:10.5194/acpd-10-24853-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
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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.
Middle atmosphere response to the solar cycle in irradiance and ionizing particle precipitation
K. Semeniuk1, V. I. Fomichev1, J. C. McConnell1, C. Fu2, S. M. L. Melo2, and I. G. Usoskin3
1Department of Earth and Space Science and Engineering, York University, Toronto, Ontario, Canada
2Canadian Space Agency, St.-Hubert, Quebec, Canada
3Sodankylä Geophysical Laboratory, University of Oulu, Oulu, Finland

Abstract. The impact of NOx and HOx production by three types of energetic particle precipitation (EPP), aurora, solar proton events and galactic cosmic rays is examined using a chemistry climate model. Ensemble simulations forced by transient EPP derived from observations with one-year repeating sea surface temperatures and fixed chemical boundary conditions were conducted for cases with and without solar cycle in irradiance. Our model results show a wintertime polar stratosphere ozone reduction of between 3 and 10% in agreement with previous studies. EPP is found to modulate the radiative solar cycle effect in the middle atmosphere in a significant way, bringing temperature and ozone variations closer to observed patterns. The Southern Hemisphere polar vortex undergoes an intensification from solar minimum to solar maximum instead of a weakening. This changes the solar cycle variation of the Brewer-Dobson circulation, with a weakening during solar maxima compared to solar minima. In response, the tropical tropopause temperature manifests a statistically significant solar cycle variation resulting in about 4% more water vapour transported into the lower tropical stratosphere during solar maxima compared to solar minima. This has implications for surface temperature variation due to the associated change in radiative forcing.

Citation: Semeniuk, K., Fomichev, V. I., McConnell, J. C., Fu, C., Melo, S. M. L., and Usoskin, I. G.: Middle atmosphere response to the solar cycle in irradiance and ionizing particle precipitation, Atmos. Chem. Phys. Discuss., 10, 24853-24917, doi:10.5194/acpd-10-24853-2010, 2010.
 
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