Impact of the lower thermospheric winter-to-summer residual circulation on thermospheric composition

Abstract
<p>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<sub>2</sub>). We found that the upwelling associated with the residual circulation significantly decreases O/N<sub>2</sub> in winter and the downwelling in summer slightly increases O/N<sub>2</sub>. Consequently, the residual circulation reduces the summer-to-winter latitudinal gradient of O/N<sub>2</sub>, which causes the simulated latitudinal gradient of O/N<sub>2</sub> to be more consistent with observations. The smaller summer-to-winter latitudinal gradient of O/N<sub>2</sub> 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.</p>
Year of Publication
2017
Journal
Geophysical Research Letters
Volume
44
Number of Pages
3971-3979
Date Published
05/2017
URL
http://doi.wiley.com/10.1002/2017GL073361
DOI
10.1002/2017GL073361