Four‐Dimensional Quantification of Kelvin‐Helmholtz Instabilities in the Polar Summer Mesosphere Using Volumetric Radar Imaging

Chau, Jorge L.; Urco, Juan Miguel; Avsarkisov, Victor; Vierinen, Juha; Latteck, R.; Hall, Chris M.; Tsutsumi, Masaki

doi:10.1029/2019gl086081

Cited by 22 publications

(41 citation statements)

References 43 publications

(59 reference statements)

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“…The billow root‐mean‐square vertical velocity U z = 29 ms −1 was obtained from the triangulation in Figure 8; and, similar to Chau et al. (2020), we calculate root‐mean‐square horizontal velocity

U_{x} \sim \frac{U_{z} L_{x}}{L_{z}} = 39.5 {ms}^{- 1} .

…”

Section: Resultssupporting

confidence: 58%

“…In a recent study, Chau et al. (2020) used radar imaging observations of a KHI at a lower altitude in the mesosphere to obtain detail comparable to the case presented here. The summertime measurements from the high‐latitude Middle Atmosphere Alomar Radar System showed the presence of billow structure around 85‐km altitude, with Ri = 0.15 and Reynolds number Re = 3.9 × 10 4 .…”

Section: Resultsmentioning

confidence: 63%

“…The results of the KHI parameters estimated for the SEEK‐2 (Larsen et al., 2005) and the study by Chau et al. (2020) in comparison to the Super Soaker KHI. The U x = 39.5 ms −1 represents the calculated version from Equation , while U x = 42.5 ms −1 represents the direct measurement through triangulation.…”

Section: Resultsmentioning

confidence: 94%

“…As discussed in the introduction, most observations of similar instability events have been made in the mesosphere (e.g., Baumgarten & Fritts, 2014; Bishop et al., 2004; Chau et al., 2020; Fritts et al., 2014; Hecht, 2005; Lehmacher et al., 2007; Pfrommer et al., 2009) where the lapse rate is usually negative and closer to the adiabatic lapse rate than at higher altitudes near the mesopause and in the lower thermosphere region. Consequently, the Brunt‐Väisälä frequency is smaller in the mesosphere as well, and more modest shears can therefore generate dynamic shear instability in this region.…”

Section: Conclusion and Discussionmentioning

confidence: 97%

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In Situ Observations of Neutral Shear Instability in the Statically Stable High‐Latitude Mesosphere and Lower Thermosphere During Quiet Geomagnetic Conditions

et al. 2020

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Though the Kelvin‐Helmholtz instability (KHI) has been extensively observed in the mesosphere, where breaking gravity waves produce the conditions required for instability, little has been done to describe quantitatively this phenomenon in detail in the mesopause and lower thermosphere, which are associated with the long‐lived shears at the base of this statically stable region. Using trimethylaluminum (TMA) released from two sounding rockets launched on 26 January 2018, from Poker Flat Research Range in Alaska, the KHI was observed in great detail above 100 km. Two sets of rocket measurements, made 30 min apart, show strong winds (predominantly meridional and up to 150 ms−1) and large total shears (90 ms−1 km−1). The geomagnetic activity was low in the hours before the launches, confirming that the enhanced shears that triggered the KHI are not a result of the E‐region auroral jets. The four‐dimensional (three‐dimensional plus time) estimation of KHI billow features resulted in a wavelength, eddy diameter, and vertical length scale of 9.8, 5.2, and 3.8 km, respectively, centered at 102‐km altitude. The vertical and horizontal root‐mean‐square velocities measured 29.2 and 42.5 ms−1, respectively. Although the wind structure persisted, the KHI structure changed significantly with time over the interval separating the two launches, being present only in the first launch. The rapid dispersal of the TMA cloud in the instability region was evidence of enhanced turbulent mixing. The analysis of the Reynolds and Froude numbers (Re = 7.2 × 103 and Fr = 0.29, respectively) illustrates the presence of turbulence and weak stratification of the flow.

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U_{x} \sim \frac{U_{z} L_{x}}{L_{z}} = 39.5 {ms}^{- 1} .

…”

Section: Resultssupporting

confidence: 58%

Section: Resultsmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 94%

Section: Conclusion and Discussionmentioning

confidence: 97%

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In Situ Observations of Neutral Shear Instability in the Statically Stable High‐Latitude Mesosphere and Lower Thermosphere During Quiet Geomagnetic Conditions

et al. 2020

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“…The application of aperture synthesis imaging for radar, i.e., aperture synthesis radar imaging (ASRI), has been used in space physics for observing high signal to noise ratio targets (Hysell et al, 2009;Chau et al, 2019). The currently available horizontal resolution is around 0.5 • with Jicamarca, but down to 0.1 • for strong backscatter (Hysell and Chau, 2012) in the case of field-aligned ionospheric irregularities; and 0.6 • with the Middle atmosphere ALOMAR radar system (MAARSY) for polar mesospheric summer echoes (PMSE) (Urco et al, 2019).…”

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confidence: 99%

Radar Imaging with EISCAT 3D

Stamm¹,

Vierinen²,

Urco³

et al. 2020

Preprint

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Abstract. A new incoherent scatter radar called EISCAT 3D is being constructed in Northern Scandinavia. It will have the capability of producing volumetric images of ionospheric plasma parameters using aperture synthesis radar imaging. This study uses the current design of EISCAT 3D to explore the theoretical radar imaging performance and compares numerical techniques that could be used in practice. Of all imaging algorithms surveyed, the singular value decomposition with regularization gave the best results and was also found to be the most computationally efficient. The estimated imaging performance indicates that the radar will be capable of detecting features down to approximately 90x90 m at a height of 100 km, which corresponds to a ~0.05° angular resolution. The temporal resolution is dependent on the signal-to-noise ratio and range resolution. The signal-to-noise ratio calculations indicate that high resolution imaging of auroral precipitation is feasible. For example, with a range resolution of 1500 m, a time resolution of 10 seconds, and an electron density of 2·1011 m−3, the correlation function estimates for radar scatter from the E-region can be measured with an uncertainty of 5 %. At a time resolution of 10 s and an image resolution of 90x90 m, the relative estimation error standard deviation of the image intensity is 10 %. Dividing the transmitting array into multiple independent transmitters to get at multiple-input-multiple-output (MIMO) interferometer system is also studied and this technique is found to increase imaging performance through improved visibility coverage. However, an estimate shows that this reduces the signal-to-noise ratio. MIMO is therefore only useful for the most brightest targets, such as meteors, polar mesospheric summer and winter echoes, and satellites. The results show that radar imaging of is feasible with the EISCAT 3D radar, and that the use of the MIMO technique should be explored further.

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Radar observation of extreme vertical drafts in the polar summer mesosphere

Chau

Marino

Feraco

et al. 2021

Preprint

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The polar summer mesosphere is the Earth's coldest region, allowing the formation of mesospheric ice clouds. These ice clouds produce strong polar mesospheric summer echoes (PMSE) that are used as tracers of mesospheric dynamics. Here, we report the first observations of extreme vertical drafts (50 1 ms  ) in the mesosphere obtained from PMSE, characterized by velocities more than five standard deviations larger than the observed vertical wind variability. Using aperture synthesis radar imaging, the observed PMSE morphology resembles a solitary wave in a varicose mode, narrow along propagation (3-4 km) and elongated ( 10 km) transverse to propagation direction, with a relatively large vertical extent (13 km). These spatial features are similar to previously observed mesospheric bores, but we observe only one crest with much larger vertical extent and higher vertical velocities.Plain Language Summary Extreme events are ubiquitous in geophysical flows. Examples of these events are tornadoes and rogue waves in the lower atmosphere and oceans, respectively. In the mesosphere, the boundary of Earth's atmosphere and outer space, extreme events can also occur, although this region is poorly observed. Here, we present the first observations of extreme vertical velocities (50 1 ms  ) in the mesosphere, that are more than five times their expected standard deviation. These observations are possible by tracking and imaging strong mesospheric radar echoes that occur in the summer at polar latitudes, with a radar used in a radio camera mode. The morphology of our observations resembles previously observed instabilities called bores or wave walls, but with much larger vertical velocities and vertical extents.

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Four‐Dimensional Quantification of Kelvin‐Helmholtz Instabilities in the Polar Summer Mesosphere Using Volumetric Radar Imaging

Cited by 22 publications

References 43 publications

In Situ Observations of Neutral Shear Instability in the Statically Stable High‐Latitude Mesosphere and Lower Thermosphere During Quiet Geomagnetic Conditions

In Situ Observations of Neutral Shear Instability in the Statically Stable High‐Latitude Mesosphere and Lower Thermosphere During Quiet Geomagnetic Conditions

Radar Imaging with EISCAT 3D

Radar observation of extreme vertical drafts in the polar summer mesosphere

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