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Model studies of short‐term variations induced in trace gases by particle precipitation in the mesosphere and lower thermosphere
Author(s) -
Fytterer T.,
Bender S.,
Berger U.,
Nieder H.,
Sinnhuber M.,
Wissing J. M.
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2015ja022291
Subject(s) - thermosphere , trace gas , atmospheric sciences , daytime , northern hemisphere , mesosphere , altitude (triangle) , ionization , solar cycle , environmental science , latitude , earth's magnetic field , atmosphere (unit) , climatology , ionosphere , physics , meteorology , geology , stratosphere , geodesy , solar wind , geophysics , ion , geometry , mathematics , quantum mechanics , magnetic field
The 3‐D global chemistry and transport model (3dCTM) was used to investigate NO, OH, and O 3 from January 2002 to May 2010 between 60 km and 133 km. Their daytime and nighttime mean zonal means (55°–75° geomagnetic latitude) were analyzed with respect to short‐term variations associated with particle precipitation. The corresponding ionization rates were derived from the 3‐D atmospheric ionization module Osnabrück (AIMOS), which is based on particle flux measurements. The trace gas variations with respect to their background were investigated by using a superposed epoch analysis. The 27 day signature associated with particle precipitation is found in NO, while it is only indicated in OH and O 3 during winter. A varying solar spectrum associated with the 11 year solar cycle causes modifications of this signal up to 10%, while the main patterns are conserved. Published observations show a clear 27 day signal, qualitatively agreeing with the model results at altitudes >70 km except for O 3 in Northern Hemisphere winter. Further differences occur with respect to the magnitude of the trace gas variations, primarily attributed to the different trace gas background and dynamical variations of the background atmosphere. Absolute OH variations are overestimated by the 3dCTM during winter, while the opposite is true for O 3 . These differences might originate from an unknown offset in AIMOS, incorrect chemical reaction rates, a different background of H 2 O and O 3 , and the model dynamics. However, their nonlinear relationship and their altitude of largest response are qualitatively captured in Southern Hemisphere winter.