Modeling the implications of Kelvin‐Helmholtz instability dynamics for airglow observations. Issue 14 (31st July 2014)

• Record Type: Journal Article
• Authors: Fritts, David C.; Wan, Kam; Werne, Joseph; Lund, Thomas; Hecht, James H.
• Is Part Of: Journal of geophysical research. Volume 119:Issue 14(2014)
• Page Start: 8858
• Page End: 8871
• Publication Date: 2014-07-31
• Subjects: Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2014JD021737
• Languages: English
• ISSNs: 2169-897X

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>A companion paper describes high‐resolution, ground‐based imaging of apparent Kelvin‐Helmholtz instabilities (KHI) observed in OH airglow at ~87 km over the Andes Lidar Observatory at 30°S. Here we employ direct numerical simulations (DNSs) and large eddy simulations (LESs) of KHI at Richardson numbers from <italic>Ri</italic> = 0.05 to 0.20 and relatively high Reynolds numbers of <italic>Re</italic> ~2500 to 10, 000 to illustrate the dependence of primary and secondary KHI on these quantities for the purpose of quantifying KHI dynamics observed by ground‐based airglow imagers. Our DNS and LES reveal significant variations of both primary and secondary KHI scales and amplitudes with varying <italic>Ri</italic> and <italic>Re</italic>. Lower <italic>Ri</italic> and higher <italic>Re</italic> yield stronger and deeper initial 2‐D KH billows. Low <italic>Re</italic> for a given <italic>Ri</italic> either yield larger‐scale 3‐D secondary instabilities or suppress them altogether. Secondary instability scales decrease as <italic>Re</italic> increases for a given <italic>Ri</italic>. Corresponding variations in implied KHI airglow signatures include (1) stronger airglow intensity variations for larger KHI wavelengths and depths (higher <italic>Ri</italic>), (2) stronger 2‐D and 3‐D responses for the initial KHI shear layer displaced somewhat from the airglow layer, and (3) stronger 3‐D responses for the lower <italic>Ri</italic> and intermediate <italic>Re</italic> yielding the larger secondary instability scales.</p> </abstract>