Gravity Wave Breaking and Vortex Ring Formation Observed by PMC Turbo

Geach, Christopher; Hanany, Shaul; Fritts, David C.; Kaifler, Bernd; Kaifler, Natalie; Kjellstrand, C. B.; Williams, B. P.; Eckermann, Stephen D.; Miller, Amber; Jones, Glenn; Reimuller, Jason

doi:10.1002/essoar.10503122.1

Cited by 5 publications

(12 citation statements)

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“…These and more recent modeling efforts also addressing large-scale KHI and multi-scale dynamics revealed a diversity of instabilities that have enabled interpretations of multiple instability events seen in PMC displays from the ground and stratospheric balloons (Fritts et al, 2014(Fritts et al, , 2019Miller et al, 2015). In several applications, comparisons of observed and modeled instability dynamics have allowed quantitative estimates of implied energy dissipation rates (Fritts et al, 2017;Geach et al, 2020). Most recently, Fritts, Kaifler et al (2020) described two successive mesospheric bores observed in the PMC layer and suggested that they are initiated by high-frequency GWs.…”

Section: 1029/2021jd034643 2 Of 28mentioning

confidence: 99%

“…Early and more recent examples include evidence for various instability dynamics accompanying large-amplitude GWs and strong wind shears being common and widespread. Specific examples seen in NLCs from the ground and PMCs imaged from the stratosphere include large-scale Kelvin-Helmholtz instabilities (KHI; see Baumgarten & Fritts, 2014;Witt, 1962), instability dynamics indicative of GW breaking (Fritts et al, 1993(Fritts et al, , 2017(Fritts et al, , 2019Geach et al, 2020;Miller et al, 2015), and related dynamics accompanying mesospheric bores (Fritts, Kaifler et al, 2020).…”

Section: 1029/2021jd034643 2 Of 28mentioning

confidence: 99%

“…The PMC layer peak brightness is often confined to layers having depths of ∼100–300 m or less (Baumgarten et al., 2012; Kaifler et al., 2013; Fritts et al., 2017, 2019) and the PMC brightness peak typically occurs at the lowest altitudes where further particle descent induces sublimation due to rapidly increasing temperature below. This causes PMC to be sensitive tracers of GWs on timescales of 5–10 h and to small‐scale instability dynamics occurring on shorter timescales and over more limited depths (Fritts et al., 1993, 2014, 2017, 2019; Geach et al., 2020). We will use the terms PMC and NLC interchangeably, since they differ only in how they are observed.…”

Section: Introductionmentioning

confidence: 99%

“…PMC observations revealing GW and instability dynamics, and related observations employing radars, lidars, and airglow imaging in the mesosphere and lower thermosphere (MLT), demonstrate the importance of these dynamics at larger and smaller scales (Fritts & Alexander, 2003). Such imaging also provides key insights into the same dynamics occurring below the MLT, but for which there are no comparable capabilities (see the dynamics studies employing PMC Turbo data, e.g., Fritts et al., 2019; Fritts, Kaifler et al., 2020, and Geach et al., 2020). Of these, PMC imaging is apparently the only capability for geophysical observations, and directly relates the sources and character of energy inputs to turbulence transitions and responses extending to the turbulence inner scale,

l_{0} \sim 10 - 20

m at PMC altitudes, at any altitude (Miller et al., 2015).…”

Section: Introductionmentioning

confidence: 99%

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Modeling Responses of Polar Mesospheric Clouds to Gravity Wave and Instability Dynamics and Induced Large‐Scale Motions

et al. 2021

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A gravity wave (GW) model that includes influences of temperature variations and large‐scale advection on polar mesospheric cloud (PMC) brightness having variable dependence on particle radius is developed. This Complex Geometry Compressible Atmosphere Model for PMCs (CGCAM‐PMC) is described and applied here for three‐dimensional (3‐D) GW packets undergoing self‐acceleration (SA) dynamics, breaking, momentum deposition, and secondary GW (SGW) generation below and at PMC altitudes. Results reveal that GW packets exhibiting strong SA and instability dynamics can induce significant PMC advection and large‐scale transport, and cause partial or total PMC sublimation. Responses modeled include PMC signatures of GW propagation and SA dynamics, “voids” having diameters of ∼500–1,200 km, and “fronts” with horizontal extents of ∼400–800 km. A number of these features closely resemble PMC imaging by the Cloud Imaging and Particle Size (CIPS) instrument aboard the Aeronomy of Ice in the Mesosphere (AIM) satellite. Specifically, initial CGCAM‐PMC results closely approximate various CIPS images of large voids surrounded by smaller void(s) for which dynamical explanations have not been offered to date. In these cases, the GW and instabilities dynamics of the initial GW packet are responsible for formation of the large void. The smaller void(s) at the trailing edge of a large void is (are) linked to the lower‐ or higher‐altitude SGW generation and primary mean‐flow forcing. We expect an important benefit of such modeling to be the ability to infer local forcing of the mesosphere and lower thermosphere (MLT) over significant depths when CGCAM‐PMC modeling is able to reasonably replicate PMC responses.

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Section: 1029/2021jd034643 2 Of 28mentioning

confidence: 99%

Section: 1029/2021jd034643 2 Of 28mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

l_{0} \sim 10 - 20

m at PMC altitudes, at any altitude (Miller et al., 2015).…”

Section: Introductionmentioning

confidence: 99%

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Modeling Responses of Polar Mesospheric Clouds to Gravity Wave and Instability Dynamics and Induced Large‐Scale Motions

et al. 2021

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“…At the average speed of 12.1 m/s of the laser beam at the height of the PMC layer, one 10-s-lidar profile averages over a horizontal distance of 121 m. The spot size of the laser beam at the PMC layer follows from the mean divergence of the laser beam and the slant range. Using a mean divergence angle of 67 µrad , the calculated spot size is 6.3 m. The position of the lidar beam is fixed relative to the FOVs of PMC Turbo's camera systems, 100 which have a pixel size at the position of the lidar beam of 3 m and 8 m, respectively (Kjellstrand et al, 2020) 2018 (Geach et al, 2020). Applying tracking algorithms to small-scale features in series of images acquired by the on-board cameras, the local wind speed can also be derived from measurements (Geach et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

The polar mesospheric cloud dataset of the Balloon Lidar Experiment BOLIDE

Kaifler

Kaifler²,

Rapp³

et al. 2022

Preprint

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Abstract. The Balloon Lidar Experiment (BOLIDE) observed polar mesospheric clouds (PMC) along the Arctic circle between Sweden and Canada during the balloon flight of PMC Turbo in July 2018. The purpose of the mission was to study small-scale dynamical processes induced by the breaking of atmospheric gravity waves by high-resolution imaging and profiling of the PMC layer. The primary measured variable of the lidar soundings is the time- and range-resolved volume backscatter coefficient β. These data are available at high resolution of 20 m and 10 s (Kaifler, 2021, https://zenodo.org/record/5722385). This document describes how we calculate β from the BOLIDE photon count data and balloon floating altitude. We compile information relevant for the scientific exploration of this dataset, including statistics, mean values and temporal evolution of parameters like PMC brightness, altitude and occurrence rate. Special emphasis is given to the stability of the gondola pointing, and the effect of resolution on the signal-to-noise ratio and thus the detection threshold of PMC. PMC layers were detected during 49.7 h in total, accounting for 36.8 % of the 5.7 days flight duration and a total of 178924 PMC profiles at 10 s resolution. Up to the present, published results from subsets of this dataset include the evolution of small-scale vortex rings, distinct Kelvin-Helmholtz instabilities and two pronounced mesospheric bores. The lidar soundings reveal a wide range of responses of the PMC layer to larger-scale gravity waves and breaking gravity waves including accompanying instabilities that await scientific analysis.

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Multi‐Scale Kelvin‐Helmholtz Instability Dynamics Observed by PMC Turbo on 12 July 2018: 1. Secondary Instabilities and Billow Interactions

et al. 2022

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The Polar Mesospheric Cloud (PMC) Turbulence experiment performed optical imaging and Rayleigh lidar PMC profiling during a 6‐day flight in July 2018. A mosaic of seven imagers provided sensitivity to spatial scales from ∼20 m to 100 km at a ∼2‐s cadence. Lidar backscatter measurements provided PMC brightness profiles and enabled definition of vertical displacements of larger‐scale gravity waves (GWs) and smaller‐scale instabilities of various types. These measurements captured an interval of strong, widespread Kelvin‐Helmholtz instabilities (KHI) occurring over northeastern Canada on July 12, 2018 during a period of significant GW activity. This paper addresses the evolution of the KHI field and the characteristics and roles of secondary instabilities within the KHI. Results include the imaging of secondary KHI in the middle atmosphere and multiple examples of KHI “tube and knot” (T&K) dynamics where two or more KH billows interact. Such dynamics have been identified clearly only once in the atmosphere previously. Results reveal that KHI T&K arise earlier and evolve more quickly than secondary instabilities of uniform KH billows. A companion paper by Fritts et al. (2022), https://doi.org/10.1029/2021JD035834R reveals that they also induce significantly larger energy dissipation rates than secondary instabilities of individual KH billows. The expected widespread occurrence of KHI T&K events may have important implications for enhanced turbulence and mixing influencing atmospheric structure and variability.

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Gravity Wave Breaking and Vortex Ring Formation Observed by PMC Turbo

Cited by 5 publications

References 39 publications

Modeling Responses of Polar Mesospheric Clouds to Gravity Wave and Instability Dynamics and Induced Large‐Scale Motions

Modeling Responses of Polar Mesospheric Clouds to Gravity Wave and Instability Dynamics and Induced Large‐Scale Motions

The polar mesospheric cloud dataset of the Balloon Lidar Experiment BOLIDE

Multi‐Scale Kelvin‐Helmholtz Instability Dynamics Observed by PMC Turbo on 12 July 2018: 1. Secondary Instabilities and Billow Interactions

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