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Impact of the lower thermospheric winter‐to‐summer residual circulation on thermospheric composition
Author(s) -
Qian Liying,
Yue Jia
Publication year - 2017
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl073361
Subject(s) - downwelling , thermosphere , atmospheric sciences , residual , upwelling , climatology , environmental science , atmospheric circulation , mesopause , anomaly (physics) , forcing (mathematics) , ionosphere , circulation (fluid dynamics) , f region , mesosphere , geology , oceanography , stratosphere , physics , geophysics , algorithm , condensed matter physics , computer science , thermodynamics
Gravity wave forcing near the mesopause drives a summer‐to‐winter residual circulation in the mesosphere and a reversed, lower thermospheric winter‐to‐summer residual circulation. We conducted modeling studies to investigate how this lower thermospheric residual circulation impacts thermospheric composition (O/N 2 ). We found that the upwelling associated with the residual circulation significantly decreases O/N 2 in winter and the downwelling in summer slightly increases O/N 2 . Consequently, the residual circulation reduces the summer‐to‐winter latitudinal gradient of O/N 2 , which causes the simulated latitudinal gradient of O/N 2 to be more consistent with observations. The smaller summer‐to‐winter latitudinal gradient of O/N 2 would decrease the ionosphere winter anomaly in model simulations, which would bring the simulated winter anomaly into better agreement with ionospheric observations. The lower thermospheric residual circulation may be a process that has been largely ignored but is very important to the summer‐to‐winter latitudinal gradients, as well as annual/semiannual variations in the thermosphere and ionosphere.