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Multi-Year Analysis of Short-Period Gravity Waves Over Alaska Under Various Stratospheric Weather Conditions

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Atmospheric gravity waves are major components of the dynamical atmosphere as they transfer large amounts of momentum and energy from the lower to the upper atmosphere [e.g. Fritts and Alexander, 2003]. In order to understand their influence on the state of the atmosphere, it is crucial to characterize these waves. The region where the waves have the most impact is in the upper atmosphere at altitudes between 80-110 km (~50-70 miles) , where the wave amplitude becomes so large that the wave breaks. This region is known as the mesopause , and is inherently difficult to observe. Fortunately, the mesopause region is also home to narrow layers producing very faint glow known as airglow. During night conditions, the nightglow can be detected with specially designed imaging systems measuring the intensity of the emitted light. As atmospheric gravity waves propagate through the airglow layers, they perturb these layers and imprint the signature during their passage. We present a three-year analysis of short period gravity waves measured by an airglow imager situated in Poker Flat, Alaska (65° N, 147° W). The imager is the cornerstone of the mesospheric airglow imaging and dynamics (MAID) project. This project is a collaborative effort between Utah Vally University, University of Alaska, Fairbanks and Utah State University, and employs the NICT Rayleigh Lidar System together with support observations from the co-located MF Radar and the NSF sponsored Poker Flat ISR.

The overarching goal of the project is to characterize the waves, their variability, and how stratospheric weather impacts the observed wave field. A recent study utilizing two years of data (2011-2012) showed a preponderance for eastward propagating waves, which is in stark contrast to other polar sites that have shown dominant westward motions. Furthermore, the study revealed a significant year to year variability in the observed phase speeds. In the study presented here, one year of additional data has been analyzed to further investigate the year to year variability and correlate the observed wave parameters to stratospheric weather phenomena including the Aleutian low, the polar vortex, and sudden stratospheric warming events.


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