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Sensitivity of simulated mesospheric transport of nitrogen oxides to parameterized gravity waves
Author(s) -
Meraner Katharina,
Schmidt Hauke,
Manzini Elisa,
Funke Bernd,
Gardini Angela
Publication year - 2016
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2016jd025012
Subject(s) - stratopause , mesosphere , gravity wave , atmospheric sciences , altitude (triangle) , atmosphere (unit) , thermosphere , physics , gravitational wave , momentum (technical analysis) , environmental science , stratosphere , geophysics , meteorology , astrophysics , ionosphere , geometry , mathematics , finance , economics
Gravity waves strongly influence the circulation and transport processes in the middle atmosphere. We analyze the sensitivity of the simulated mesospheric transport of nitrogen oxides (NO x ) to differences in a parameterization of nonorographic gravity waves. After particularly strong sudden stratospheric warming (SSW) events as in January 2009, satellite instruments measured a strong mesospheric descent of NO x . However, this downward transport is in general underestimated in models covering this altitude range. We use simulations of the atmospheric general circulation and chemistry model HAMMONIA (Hamburg Model of Neutral and Ionized Atmosphere) to discuss both differences in a homogeneous background gravity wave source and a source related to frontal activity. The results show that the transport of NO x is highly sensitive to such differences. With a stronger gravity wave source, less NO x is transported after the SSW to the mesosphere and the elevated stratopause descends more rapidly to its climatological altitude. We observe the opposite by weakening the gravity wave sources yielding a better agreement with the observations. The amount of the transported NO x is controlled by the altitude at which momentum is deposited in the atmosphere. The higher the altitude where the momentum is deposited in the upper mesosphere, the stronger is the descent of NO x . A small wave amplitude favors the transition to turbulence at a higher altitude due to the exponential increase of the amplitude with height.