Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsa11a1455s&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #SA11A-1455
Physics
[0310] Atmospheric Composition And Structure / Airglow And Aurora, [3332] Atmospheric Processes / Mesospheric Dynamics, [3384] Atmospheric Processes / Acoustic-Gravity Waves
Scientific paper
Atmospheric gravity waves at a broad range of temporal and spatial scales are frequently observed in MLT airglow imaging experiments. Airglow data provide significant insight into gravity wave propagation, directionality, and seasonality, and allow estimations of wave fluxes [e.g., Swenson et al., JGR, 104(D6), 1999]. The USU CEDAR Mesospheric Temperature Mapper (MTM) is a specialized CCD airglow imaging system, which was operated at Maui MALT from November 2001 to December 2006. The MTM captures OH(6,2) and O2(0,1) emissions intensities and associated rotational temperatures. The MTM has been used previously to assess zenith temperatures, showing close agreement with simultaneous lidar temperature data [Zhao et al., J. Geophys. Res., 110, D09S07, 2005]. It is additionally able to reveal two-dimensional structure of intensity and temperature perturbations associated with small-scale gravity waves. Here we investigate the vertical and horizontal structure of a small-scale gravity wave (~18 minute period and ~37 km horizontal wavelength) captured by the Maui MTM on April 11, 2002. The event was strongly visible in the OH(6,2) image data, showing intensity perturbations ~ 5-10 %, however relatively weak in the O2 data. Lidar temperatures and winds suggest the presence of a critical level shortly above ~90 km, which would have contributed to increased dissipation, and reduced detectability, due to small vertical scale. Using imaged intensity and rotational temperature data, along with evolving Na lidar data, we reconstruct and simulate the wave event under realistic ambient conditions using a suite of numerical models. Hydroxyl photochemistry and dynamics of O3, H, O, and Na densities are obtained with a two-dimensional nonlinear numerical model for gravity wave dynamics [Snively and Pasko, JGR, 113, A06303, 2008], allowing direct comparison of OH(6,2) intensity and brightness-weighted temperature perturbations [e.g., Makhlouf et al., JGR, 100(D6), 11289, 1995]. The strong sheared wind flow leads to dramatic variations of wave characteristics throughout the observable region, explaining the strong OH emission and relatively weak O2 emission. Krassovsky ratios and integrated cancellation effects of the modeled and observed airglow signatures are investigated, finding significant agreement, and inferred wave amplitude measurements are compared with modeled wave characteristics. Implications for wave momentum flux calculations from lidar and airglow data are discussed.
Pautet P.
Snively Jonathan B.
Swenson Gary R.
Taylor Mary Jane
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