Middle-atmosphere tides: Recent advances in theory and observation

Recent progress in the theoretical and observational investigation of middle atmosphere tides is reviewed. Theoretical advances include development of more realistic thermal excitation and numerical simulation models, investigation of seasonal — latitudinal and longitudinal variations in tidal structures, and the origin and effects of ‘unsteadiness’ in tidal oscillations over periods of days. Recent analyses of middle latitude radar data between 80 Km and 130 Km delineate consistent seasonal phase patterns in this region. Analyses of rocket data show stratosphere and lower mesosphere tides to be characterized by smaller amplitudes, shorter vertical scales, greater unsteadiness, and greater spatial variability than exhibited in the upper mesosphere and above. Results from the first two ATMAP (Atmospheric Tides Middle Atmosphere Program) campaigns are also discussed.