Short-period gravity waves of especially-small horizontal scale have beenobserved in the Maui, Hawaii airglow. Typical small-scale gravity wave eventshave been investigated, and intrinsic wave propagation characteristics havebeen calculated from simultaneous meteor radar wind measurements. Here wereport specific cases where wave structure is significantly determined by thelocal wind structure, and where wave characteristics are consistent withducted or evanescent waves throughout the mesopause region. Two of thedocumented events, exhibiting similar airglow signatures but dramaticallydifferent propagation conditions, are selected for simple numerical modelingcase studies. First, a Doppler-ducted wave trapped within relatively weakwind flow is examined. Model results confirm that the wave is propagating inthe 85–95 km region, trapped weakly by evanescence above and below. Second,an evanescent wave in strong wind flow is examined. Model results suggest anopposite case from the first case study, where the wave is instead trappedabove or below the mesopause region, with strong evanescence arising in the85–95 km airglow region. Distinct differences between the characteristics ofthese visibly-similar wave events demonstrate the need for simultaneousobservations of mesopause winds to properly assess local propagationconditions.
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