講演情報
[PEM10-11]Impact of the lower thermospheric winter-to-summer residual circulation on thermospheric composition★Invited Papers
*Liying Qian1、Jia Yue2,3 (1.University Corporation for Atmospheric Research、2.Center for Atmospheric Science, Hampton University、3.ESSIC, University of Maryland College Park)
キーワード：
Thermosphere Circulation、Thermosphere Composition、Ionosphere Winter Anomaly
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 impact thermospheric composition (O/N2). We found that the upwelling associated with the residual circulation significantly decreases O/N2 in winter and the downwelling in summer slightly increases O/N2. Consequently, the residual circulation reduces the summer-to-winter latitudinal gradient of O/N2, which causes the simulated latitudinal gradient of O/N2 to be more consistent with observations. The smaller summer-to-winter latitudinal gradient of O/N2 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.