CEDAR: Mesospheric Dynamics with Airglow Imaging, Photometry and Meteor Radar

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Atmospheric Gravity Waves (AGWs) are a major contributor to the dynamics and thermal balance in the mesosphere. This study has several objectives which will address the need for quantitative measurements of AGWs and their signatures in the mesosphere and lower thermosphere. The results will improve understanding of AGW dynamics and help global circulation models to make more accurate simulation of the global climate change with better gravity wave parameterization. Measurements will be carried out using an OH imager, a multi-channel photometer, and a meteor radar. This instrumentation is currently located at Maui, HI and will be re-located to a South American site near Cerro Tololo, Chile (30 S, 71 W). These instruments will be co-located with the University of Illinois Na lidar which will provide high resolution temperature and wind in the same region. The science objectives are: (1) to use OH airglow imagery to measure and study the vertical flux of horizontal momentum carried by AGWs with large vertical wavelengths, which carry the major portion of the wave momentum flux in the mesosphere. The meteor radar will supply wind measurements to be used for Doppler correction of observed phase speeds. The lidar observes slower speed AGWs that complement the spectrum observed in airglow. The direction and magnitude of the fluxes, and their variation with season, will be characterized. Comparisons will be made to similar measurements from other geographic locations and with the intensity and temperature perturbations from the Utah State University Mesospheric Temperature Mapper; (2) to measure and study the vertical propagation direction of short-horizontal-scale AGWs, and to determine the significance of ducted waves in airglow observations. Upward propagating momentum may be cancelled by downward propagating waves, and several investigations have found conditions suggesting ducting may be significant for short horizontal wavelengths. This study will statistically quantify occurrence probabilities for upward/downward propagation, and ducting for waves observed in airglow. The data for this study will be from photometer measurements with high time resolution of the OH molecule which is concentrated in a layer near 86 km and of the O2 atmospheric band, concentrated near 94 km; (3) to understand the large amplitude events observed in airglow images, including "wall waves". Although these events are rare, they may have significant impacts on the atmosphere and the instrument suite will provide geophysical insight into these dramatic events over the South American site. The broader impacts of the project include collaborations with other investigators at the University of Illinois, Utah State, and the Aerospace Corporation. This project will support one graduate student, whose research will comprise the Master's of Science thesis project. Undergraduate students will be involved in the research through participation in independent study projects. Publications and presentations of results will be made throughout the program.