Kelvin twist waves in the transition to turbulence

Arendt, Steve; Fritts, David C.; Andreassen, Øyvind

doi:10.1016/s0997-7546(98)80014-9

Cited by 16 publications

(9 citation statements)

References 24 publications

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“…Intertwined vortex loops, or similar “hairpin” or “horseshoe” vortices, are seen to arise in sheared boundary layers [ Gerz et al , 1994; Adrian et al , 2000]; twist waves, so easily excited in the wave breaking simulations, were also observed, but not recognized as such, in laboratory studies of vortex dynamics [ Cadot et al , 1995]. Finally, the sequence of vortex dynamics seen in gravity wave breaking exhibits striking parallels to that observed in the transition to turbulence accompanying the KH instability to be discussed below [see also Arendt et al , 1997, 1998; Fritts et al , 1999]).…”

Section: Interactions Instability and Saturationmentioning

confidence: 99%

Gravity wave dynamics and effects in the middle atmosphere

Fritts

Alexander

2003

Reviews of Geophysics

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[1] Atmospheric gravity waves have been a subject of intense research activity in recent years because of their myriad effects and their major contributions to atmospheric circulation, structure, and variability. Apart from occasionally strong lower-atmospheric effects, the major wave influences occur in the middle atmosphere, between ϳ 10 and 110 km altitudes because of decreasing density and increasing wave amplitudes with altitude. Theoretical, numerical, and observational studies have advanced our understanding of gravity waves on many fronts since the review by Fritts [1984a]; the present review will focus on these more recent contributions. Progress includes a better appreciation of gravity wave sources and characteristics, the evolution of the gravity wave spectrum with altitude and with variations of wind and stability, the character and implications of observed climatologies, and the wave interaction and instability processes that constrain wave amplitudes and spectral shape. Recent studies have also expanded dramatically our understanding of gravity wave influences on the large-scale circulation and the thermal and constituent structures of the middle atmosphere. These advances have led to a number of parameterizations of gravity wave effects which are enabling ever more realistic descriptions of gravity wave forcing in large-scale models. There remain, nevertheless, a number of areas in which further progress is needed in refining our understanding of and our ability to describe and predict gravity wave influences in the middle atmosphere. Our view of these unknowns and needs is also offered. INDEX TERMS: 3319

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Section: Interactions Instability and Saturationmentioning

confidence: 99%

Gravity wave dynamics and effects in the middle atmosphere

Fritts

Alexander

2003

Reviews of Geophysics

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2,264

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“…The process is common in vortex interactions accompanying the turbulence cascade to smaller scales. Perturbations leading to breakup of the initial billow core are known as Kelvin “twist waves” [ Kelvin , ], which have been identified and analyzed in previous numerical simulations of GW breaking [e.g., Andreassen et al ., ; Fritts et al ., , , ] and diagnosed theoretically [e.g., Arendt et al ., , ]. The subsequent evolution of the separate billow cores is surely influenced by the stable stratification at the larger scales on which the KHI is evolving, in contrast to typically weaker stratification for small‐scale vortices interacting within a turbulence field.…”

Section: Assessments Of Khi and Environmental Parameters In Nlc Imagesmentioning

confidence: 99%

Quantifying Kelvin‐Helmholtz instability dynamics observed in noctilucent clouds: 2. Modeling and interpretation of observations

et al. 2014

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A companion paper describes high-resolution, ground-based imaging of apparent Kelvin-Helmholtz instabilities (KHI) observed in noctilucent clouds (NLCs) near the polar summer mesopause. Here we employ direct numerical simulations of KHI at Richardson numbers from Ri = 0.05 to 0.20 and relatively high Reynolds numbers to illustrate the dependence of KHI and secondary instabilities on these quantities and interpret and quantify the KHI events described by Baumgarten and Fritts (2014). We conclude that one event triggered by small-scale gravity waves provides clear evidence of strong KHI initiated at Ri~0.05-0.10. Events arising in a more uniform shear environment exhibit KHI and small-scale dynamics that compare reasonably well with modeled KHI initiated at Ri~0.20. Our application of numerical modeling in quantifying KHI dynamics observed in NLCs suggests that characteristics of KHI, and perhaps other small-scale dynamics, that are defined well in NLC displays can be used to quantify the dynamics and spatial scales of such events with high confidence. Specifically, our comparisons of KHI observations and modeling appear to indicate a "turbulent" viscosity~5-40 times the true kinematic viscosity at the NLC altitude. This offers an alternative, or an augmentation, to more traditional radar, lidar, and/or airglow measurements employed for such studies of small-scale dynamics at coarser spatial scales during polar summer.

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“…The streamwise‐aligned rolls comprising secondary instability within the 2‐D KH billows initiate a transition to full turbulence via mutual and self vortex interactions. These interactions were initially described in numerical simulations of gravity‐wave breaking by Arendt et al [1998] and Fritts et al [1998] and in our initial KH simulations by Fritts and Werne [2000]. Essentially, the interactions among neighboring vortices spawn a series of perturbations to the vortices that can be viewed most simply as twist waves [ Kelvin , 1880; Arendt et al , 1997].…”

Section: Turbulence Generation and Layering Accompanying Kh Instabilitymentioning

confidence: 99%

Layering accompanying turbulence generation due to shear instability and gravity‐wave breaking

et al. 2003

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[1] We describe and compare idealized high-resolution simulations of turbulence arising due to Kelvin-Helmholtz shear instability and gravity-wave breaking, believed to be the two major sources of turbulence generation near the mesopause. The two flows both share characteristics related to turbulence transition, evolution, and duration and exhibit a number of differences that have important implications for layering, layered structures, and atmospheric observations at mesopause altitudes. Common features related to layering include sharp local gradients in turbulent kinetic energy production, dissipation, and magnitude and a clear spatial separation of the maxima of turbulent kinetic energy dissipation and thermal dissipation accompanying vigorous turbulence. Differences arise because shear instability causes turbulence and mixing confined by stratification to a narrow layer, whereas gravity-wave breaking leads to a maximum of turbulence activity that moves with the phase of the wave. As a result, the effects of turbulence due to shear instability likely persist for much longer than those of turbulence due to gravity-wave breaking. We also discuss the implications of these results for a number of atmospheric measurements employing radar.

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Kelvin twist waves in the transition to turbulence

Cited by 16 publications

References 24 publications

Gravity wave dynamics and effects in the middle atmosphere

Gravity wave dynamics and effects in the middle atmosphere

Quantifying Kelvin‐Helmholtz instability dynamics observed in noctilucent clouds: 2. Modeling and interpretation of observations

Layering accompanying turbulence generation due to shear instability and gravity‐wave breaking

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