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Journal Article

Transport of Nitrogen Oxides through the winter mesopause in HAMMONIA

MPS-Authors
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Meraner,  Katharina
Middle and Upper Atmosphere, The Atmosphere in the Earth System, MPI for Meteorology, Max Planck Society;
IMPRS on Earth System Modelling, MPI for Meteorology, Max Planck Society;

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Schmidt,  Hauke
Middle and Upper Atmosphere, The Atmosphere in the Earth System, MPI for Meteorology, Max Planck Society;

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Supplementary Material (public)
Citation

Meraner, K., & Schmidt, H. (2016). Transport of Nitrogen Oxides through the winter mesopause in HAMMONIA. Journal of Geophysical Research-Atmospheres, 121, 2556-2570. doi:10.1002/2015JD024136.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0029-731D-D
Abstract
We analyze the importance of individual transport processes for the winter polar downward transport of nitrogen oxides (NOx) from the thermosphere to the mesosphere. The downward transport of NOx produced by energetic particle precipitation induces chemical alterations in the middle atmosphere and influences ozone chemistry. However, it remains unclear how much each transport process contributes to the downward transport. We use simulations of the atmospheric general circulation and chemistry model HAMMONIA (Hamburg Model of Neutral and Ionized Atmosphere) for the extended winter 2008/2009 with a passive tracer. The model enables us to separate the contributions of advection, eddy and molecular diffusion on the total transport by switching off processes. The results show that molecular diffusion and resolved vertical mixing due to advection effectively transport NOx to the mesosphere. While the impact of molecular diffusion on the transport rapidly decreases below 0.001 hPa, the impact of advection increases. Around the central date of the sudden stratospheric warming in January 2009, advection is strongly enhanced in the thermosphere and mesosphere and the downward transport through the mesopause region is almost entirely driven by advection. Eddy diffusion has limited impact on the transport in the upper mesosphere and negligible impact on the transport in the thermosphere. If eddy diffusion is enhanced as suggested by observations, it can potentially have a larger impact on transport through the mesopause than was previously assumed.