The Relative Roles of Dynamics and Energetic Particle Precipitation in Driving Variability of High-Latitude Mesospheric NOx

Thursday, 18 December 2014: 8:50 AM
Daniel Robert Marsh1, Mark A. Clilverd2, Douglas Edward Kinnison1, Craig J Rodger3 and Pekka T Verronen4, (1)National Center for Atmospheric Research, Boulder, CO, United States, (2)British Antarctic Survey, Cambridge, United Kingdom, (3)University of Otago, Dunedin, New Zealand, (4)Finnish Meteorological Inst., Helsinki, Finland
The concentration of odd-nitrogen species (NOx) in the winter polar mesophere depends on several factors, including the state of stratospheric winds, the strength of diffusive transport near the mesopause, and the deposition of energetic particles in the mesosphere and the lower thermosphere (MLT). This paper presents a series of model experiments using the NCAR Whole Atmosphere Community Climate Model that explores the sensitivity of MLT NOx to these factors and how they vary in importance between the hemispheres. Two that appear to play an important role in the Southern Hemisphere are the Prandtl number used to calculate the diffusivity due to gravity waves and the inclusion of medium energy electrons. In the Northern Hemisphere, as previously reported, the concentration of NOx additionally depends on if and when a stratospheric sudden warming occurs. The representation of these processes significantly affects the amount of NOx entering the stratosphere and subsequent EPP-induced ozone loss.