Gravity Wave Breaking and Vortex Ring Formation Observed by PMC Turbo. Issue 23 (25th November 2020)

• Record Type: Journal Article
• Authors: Geach, C.; Hanany, S.; Fritts, D. C.; Kaifler, B.; Kaifler, N.; Kjellstrand, C. B.; Williams, B. P.; Eckermann, S. D.; Miller, A. D.; Jones, G.; Reimuller, J.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 23(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-25
• Subjects: convective instability -- gravity wave breaking -- vortex rings -- polar mesospheric clouds -- mesosphere; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2020JD033038
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Polar mesospheric cloud (PMC) imaging and lidar profiling performed aboard the 5.9‐day PMC Turbo balloon flight from Sweden to northern Canada in July 2018 revealed a wide variety of gravity wave (GW) and instability events occurring nearly continuously at approximately 82 km. We describe one event exhibiting GW breaking and associated vortex rings driven by apparent convective instability. Using PMC Turbo imaging with spatial and temporal resolution of 20 m and 2 s, respectively, we quantify the GW horizontal wavelength, propagation direction, and apparent phase speed. We identify vortex rings with diameters of 2–5 km and horizontal spacing comparable to their size. Lidar data show GW vertical displacements of ±0.3 km. From the data, we find a GW intrinsic frequency and vertical wavelength of 0.009 ± 0.003 rad s −1 and 9 ± 4 km, respectively. We show that these values are consistent with the predictions of numerical simulations of idealized GW breaking. We estimate the momentum deposition rate per unit mass during this event to be 0.04 ± 0.02 m s −2 and show that this value is consistent with the observed GW. Comparison to simulation gives a mean energy dissipation rate for this event of 0.05–0.4 W kg −1, which is consistent with other reported in situ measurements at the Arctic summer mesopause. Key Points: Gravity wave breaking and associated vortex rings are observed in imaging and lidar data of polar mesospheric clouds Analysis of the data gives parameters of the gravity wave and rates of energy and momentum transfer due to its breaking Observed vortex ring parameters agree with predictions by numerical resolutions of gravity wave breaking