Summary
A decade of radiosonde observations of wind and temperature in the troposphere and lower stratosphere have made it possible to compile a climatology of low-frequency gravity waves above Davis, Antarctica (69S, 78E). Wave characteristics, extracted using wavelet analysis [Zink and Vincent, 2001], show strong seasonal and height variations. In particular, the high prevalence of down-going waves in the winter lower stratosphere previously identified at other Antarctic sites [Moffat-Griffin et al. 2011; Yoshiki and Sato, 2000] has been shown to exist at Davis. The vertical structure and seasonal variation of down-going wave percentages are shown in Figure 1a, and a relationship with the background zonal wind structure (contoured) is suggested. Figures 1b and 1c show that the down-going waves replace up-going waves in the winter lower stratosphere. Statistical distributions of the characteristics of the up and down-going waves show strong similarities suggesting a common source. It is also possible that both classes of waves have characteristics that are more strongly dependent on propagation conditions than their source mechanism. It has been suggested [Sato and Yoshiki, 2008] that imbalance processes in the polar night jet may play a role in their production. This possibility is considered along with the propagation characteristics of the waves to explore their role in the dynamics of the polar stratosphere, and to examine the adequacy of their representation in atmospheric models. References: Moffat-Griffin, T., R. E. Hibbins, M. J. Jarvis and S. R. Colwell, Seasonal variations of gravity wave activity in the lower stratosphere over an Antarctic Peninsula station, J. Geophys. Res., 116, D14111, doi:10.1029/2010JD015349, 2011. Sato, K. And M. Yoshiki, Gravity wave generation around the polar vortex in the stratosphere revealed by 3-hourly radiosonde observations at Syowa station, J. Atmos. Sci., 65, 3719-3735, 2008. Yoshiki, M. And K. Sato, A statistical study of gravity waves in the polar regions based on operational radiosonde data, J. Geophys. Res., 105, D14, 17995-18011, 2000. Zink, F. and R. A. Vincent, Wavelet analysis of stratospheric gravity wave packets over Macquarie Island 1. Wave parameters, J. Geophys. Res., 106, 10275-10288, 2001.
Related projects
