This is a multinational, multi.investigator, project to analyze a diversity of existing optical and radar data sets describing the climatology of the atmosphere at 70.100 kilometers over Antarctica, and to develop a model of the dynamics of this region of the antarctic atmosphere based on the observations. The objective is to characterize the meteorology of the antarctic mesosphere and lower thermosphere (MALT), and to determine how it compares with (and differs from) the complementary arctic region. The emphasis will be placed on understanding the winds and tides. Of particular topical interest are studies of the height and seasonal.latitude structures of turbulent diffusivities implied by gravity wave and tidal breaking, with a particular view towards evaluating the accessibility of nitrogen oxide (NO), produced by energetic particle precipitation in the high magnetic latitude upper atmosphere, to stratospheric levels where it can catalytically destroy ozone.