Collaborative Research: CEDAR: Large Amplitude Variations & Instabilities due to Strong Interactions between Tides & Planetary Waves in the Upper Mesosphere and Lower Therm

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This project is to characterize the role of nonlinear interactions, including instability, between tides and traveling and stationary planetary waves in generating variability in the upper mesosphere and lower thermosphere (MLT). The work will focus particularly on the two day wave (TDW) in the summertime southern hemisphere, including studies on its amplification due to resonance with a subharmonic of the diurnal tide and consequent generation of a parametric subharmonic instability (PSI) as well as on the apparent association between phase-locked TDWs and pronounced enhancements of airglow emission brightness. In addition, this project will investigate nonlinear forcing mechanisms which modulate tidal amplitude and/or produce non-migrating tides, particularly the westward semidiurnal tide which is dominant in the high-latitude upper mesosphere. This effort will utilize a systems science methodology which combines ground-based wind and airglow intensity measurements, temperature measurements from the NASA TIMED satellite, the TIME-GCM general circulation model, and a global data assimilation model. This work will be conducted as a collaboration between international and U.S. educational, research, and small business institutions.