ABSTRACT

The 80 to 100 km altitude regime, commonly known as the MALT (upper Mesosphere and Lower Thermosphere), is a region of the atmosphere where the mean-state is largely controlled by waves and wave-driven process. Wave instabilities related to wave breakdown play a key role in the MALT, inducing the deposition of wave momentum deposition and eddy mixing. Characterization of these processes is essential for comprehensive understanding and modeling of the MALT region. Modern, automated airglow imagers provide a unique platform for studying a wide range of waves and instabilities and are able to collect data nearly continuously over long periods of time, which is essential for climatological studies. This project will provide multiple measurements and observational analyses that address outstanding questions concerning the role of wave and instabilities in the MALT: (A) Which type of instability, convective or dynamic, is better correlated with the presence of instabilities in airglow images? (B) How common are evanescent waves in airglow images? Can they be related to parametric instability, and/or are they correlated with the presence of convectively-formed ripples? (C) How significantly do gravity waves affect the airglow temperature and intensity climatology of the MALT in the Australian sector? Does their variability correlate with differences between observations and the TIME-GCM model? (D) Can airglow observations of atmospheric gravity waves distinguish between local or distant convective sources? (E) How are periods of unusually intense airglow or strong mesospheric bores related to gravity waves or modifications of the background state by planetary waves, such as the two-day wave?

Airglow data from three existing Aerospace imagers will be used to address these questions. A single imager will be deployed in coordination with the upgraded University of Illinois lidar, which will be redeployed to a site near Cerro Tololo Chile. This imager was previously used during the MauiMALT campaign; continuing operation of the imager with the improved lidar is expected to improve upon results obtained during that successful campaign. The remaining two imagers will remain in Adelaide and Alice Springs, Australia. These imagers have been operating nearly continuously for the past five years, yielding a vast amount of climatological and gravity wave data in the unique Australian sector. A lidar will soon be added to the suite of ground-based instrumentation at Adelaide, which currently includes radar and airglow spectrometers. The Australian sites therefore provide a unique opportunity for both multiple-instrument and multiple-imager observations of the MALT region. The broader impacts of the project include the following: (1) the establishment and maintenance of an infrastructure of advanced airglow imagers; (2) the provision of the observational database to the entire scientific community via a website, including data to be used for student thesis research; (3) collaborations with US and international scientists, encouraging access to varied data sets and resources; (4) the support of other coordinated multi-instrument investigations at the imager sites; and (5) journal publications and scientific presentations.

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