CEDAR: Climatology and Characteristics of Instabilities and Atmospheric Gravity Waves at Low and Mid Latitudes

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Optical and near infrared imaging data from three sites are used to investigate the source and characteristics of gravity waves at low and mid-latitudes. Extant data from sites at the Maui MALT (Mesosphere and Lower Thermosphere) Atmospheric Observatory in Hawaii, at Adelaide Australia, and at Alice Springs Australia are analyzed, and new data are gathered. The imager at Maui Malt samples extremely bright OH Meinel emissions near 1600 nm, and is therefore capable of very fast sampling, achieving a signal-to-noise ration of 100 in one second. This imager is uniquely capable of capturing fast moving, short period gravity wave structures, and will be used to examine the possibility of a peak in gravity wave periods near the Brunt-Vaisala period (nominally five minutes), and the corresponding possibility of a sharp frequency cutoff for gravity wave periods shortward of this period. The Maui MALT imager data are also used to characterize the nature of small-scale instability features in the OH airglow layer. The relationship of these features to convectively unstable layers as well as the thickness of these layers is determined, and the morphology and climatology of these instabilities is characterized. The instruments in Australia are conventional optical imagers, separated by 1500 km. Data from these sites are used to examine a possible tropospheric convective source centered approximately 1300 km north of Alice Springs in Darwin. Due to the absence of orographic features between Alice Springs and Adelaide, the Australian imagers offer an excellent opportunity to isolate the role of tropospheric sources of MALT gravity waves.