Atmos. Chem. Phys. Discuss., 8, 10561-10596, 2008
www.atmos-chem-phys-discuss.net/8/10561/2008/
doi:10.5194/acpd-8-10561-2008
© Author(s) 2008. 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.
Mesospheric N2O enhancements as observed by MIPAS on Envisat during the polar winters in 2002–2004
B. Funke1, M. López-Puertas1, M. García-Comas1, G. P. Stiller2, T. von Clarmann2, and N. Glatthor2
1Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain
2Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung (IMK), Karlsruhe, Germany

Abstract. N2O abundances ranging from 0.5 to 6 ppbv were observed in the polar upper stratosphere/lower mesosphere by the MIPAS instrument on the Envisat satellite during the Arctic and Antarctic winters in the period July 2002 to March 2004. A detailed study of the observed N2O–CH4 correlations shows that such enhancements are of chemical rather than dynamical origin. The N2O enhancements observed at 58 km occurred in presence of NOx intrusions from the upper atmosphere which were related to energetic particle precipitation. Further, the inter-annual variability of mesospheric N2O correlates well with observed precipitating electron fluxes. The analysis of possible chemical production mechanisms shows that the major part of the observed N2O enhancements is most likely generated under dark conditions by the reaction of NO2 with atomic nitrogen at altitudes around 70–75 km in the presence of energetic particle precipitation. A possible additional source of N2O in the middle and upper polar atmosphere is the reaction of N2(A3Σu+), generated by precipitating electrons, with O2, which would lead to N2O production peaking at altitudes around 90–100 km. N2O produced by the latter mechanism could then descend to the mesosphere and upper stratosphere during polar winter.

Citation: Funke, B., López-Puertas, M., García-Comas, M., Stiller, G. P., von Clarmann, T., and Glatthor, N.: Mesospheric N2O enhancements as observed by MIPAS on Envisat during the polar winters in 2002–2004, Atmos. Chem. Phys. Discuss., 8, 10561-10596, doi:10.5194/acpd-8-10561-2008, 2008.
 
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