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| Titel |
Observation and modeling of mesospheric Na density and OH airglow perturbations by a gravity wave approaching a critical level |
| VerfasserIn |
Jonathan Snively, Pierre-Dominique Pautet, Michael Taylor, Gary Swenson, Alan Liu |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250043402
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| Zusammenfassung |
| 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 is able to reveal two-dimensional structure of
intensity and temperature perturbations associated with small-scale gravity waves,
and has been used to assess zenith temperatures, showing close agreement with
simultaneous lidar temperature data [Zhao et al., J. Geophys. Res., 110, D09S07,
2005].
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.
With imaged intensity and rotational temperature data, along with evolving
Na lidar profile 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. |
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