Modulation of upper mesospheric temperature inversions due to tidal-gravity Wave interactions

Abstract

Two nights of coincident measurements with the University of Western Ontario's MF radar and Purple Crow Lidar have been extensively analyzed to illustrate the possible effects due to tidal-gravity wave interactions on upper mesospheric inversion layers. On both nights an inversion layer in the upper mesosphere disappears as the westward component of the tide increases. Inversions similar in height and magnitude to these two nights, as seen in the nightly mean temperature profile, occur in 11% of the measurements made by the Purple Crow Lidar since 1994. Of these inversions, 76% show similar behavior to the two nights considered here in detail. The statistical results suggest the upper mesospheric inversion occur in two types. The first type, illustrated by the individual nights considered in this study, are associated with increased gravity wave variance as the magnitude of the westward tide decreases. These inversions are persistence over many hours. The second type of inversion has a similar nightly mean structure, but is due to shorter (on the order of <2 h ) periods of heating with temperature changes much greater than that expected from tidal dissipation.