Lidar observations of gravity wave activity in the middle atmosphere above Davis (69◦S, 78◦E), Antarctica

Abstract

A 16 month series of lidar measurements in the stratosphere and mesosphere/lower thermosphere (MLT) region over Davis Station (69◦S, 78◦5 E) in Antarctica is used to study 6 gravity waves. The unprecedentedly large number of observations totaling 2310 hours al7 lows us investigate in great detail seasonal variations in gravity wave activity. In the strato8 sphere the gravity wave potential energy density (GWPED) is shown to have a large sea9 sonal variation with a double peak in winter and minimum in summer. We find conser10 vative wave propagation to occur between 29 and 41 km altitude in winter as well as 11 in summer whereas smaller energy growth rates were observed in spring and autumn. 12 These results are consistent with selective critical-level filtering of gravity waves in the 13 lower stratosphere. In the MLT region the GWPED is found to have a semi-annual os14 cillation with maxima in winter and summer. The structure of the winter peak is iden15 tical to that in the stratosphere, suggesting that the gravity wave flux reaching the MLT 16 region is controlled by the wind field near the tropopause level.