Combined MU radar and ozonesonde measurements of turbulence and ozone fluxes in the tropo‐stratosphere over Shigaraki, Japan

Гаврилов, Н. М.; Fukao, S.; Hashiguchi, Hiroyuki; Kita, K.; Sato, K.; Tomikawa, Yoshihiro; Fujiwara, Masatomo

doi:10.1029/2005gl024002

Cited by 7 publications

(5 citation statements)

References 25 publications

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“…Ri loc (y) = −g dρ dy ρ dU dy 2 where g is the acceleration of gravity. It also convenient to define a global Richardson number in order to give a general measure of how strongly stratified the flow is.…”

Section: Introductionmentioning

confidence: 99%

“…If the Reynolds number is large enough then this process quickly becomes turbulent, diffusion is enhanced by the generation of small scales and the kinetic energy of the flow is converted irreversibly to potential energy. The rate kinetic energy is converted to potential energy and the total amount of potential energy gained can be of crucial importance in determining the evolution of many physically important systems, like the atmosphere [1,2], oceanic flows [3,4,5,6] and various astrophysical flows [7,8,9]. In particular in this work the generation of turbulence and mixing in strongly stratified environments is examined.…”

Section: Introductionmentioning

confidence: 99%

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Stratified shear flow instabilities at large Richardson numbers

Alexakis¹

2009

Physics of Fluids

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Numerical simulations of stratified shear flow instabilities are performed in two dimensions in the Boussinesq limit. The density variation length scale is chosen to be four times smaller than the velocity variation length scale so that Holmboe or Kelvin-Helmholtz unstable modes are present depending on the choice of the global Richardson number Ri. Three different values of Ri were examined Ri = 0.2, 2, 20. The flows for the three examined values are all unstable due to different modes namely: the Kelvin-Helmholtz mode for Ri = 0.2, the first Holmboe mode for Ri = 2, and the second Holmboe mode for Ri = 20 that has been discovered recently and it is the first time that it is examined in the non-linear stage. It is found that the amplitude of the velocity perturbation of the second Holmboe mode at the non-linear stage is smaller but comparable to first Holmboe mode. The increase of the potential energy however due to the second Holmboe modes is greater than that of the first mode. The Kelvin-Helmholtz mode is larger by two orders of magnitude in kinetic energy than the Holmboe modes and about ten times larger in potential energy than the Holmboe modes. The results in this paper suggest that although mixing is suppressed at large Richardson numbers it is not negligible, and turbulent mixing processes in strongly stratified environments can not be excluded.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Stratified shear flow instabilities at large Richardson numbers

Alexakis¹

2009

Physics of Fluids

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“…Turbulence can be responsible for vertical transport of heat and materials between the troposphere and the stratosphere through intense mixing, particularly in the sheared regions of meteorological upper-level fronts and tropopause folds at midlatitudes (e.g., Shapiro 1980;Bertin et al 2001;Koch et al 2005;Gavrilov et al 2006). KH instability may also cause aircraft hazards (Ralph et al 1997;Clark et al 2000).…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Observations with MU Radar of a KH Instability Triggered by an Inertia–Gravity Wave in the Upper Part of a Jet Stream

Luce

Hassenpflug

Yamamoto

et al. 2008

Journal of the Atmospheric Sciences

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Kelvin-Helmholtz (KH) instability is likely one of the most important sources of clear-air turbulence in the lower atmosphere. It produces billows, which mix and transport heat and materials vertically in the stably stratified atmosphere. Billows can also dissipate energy; therefore they can affect the larger-scale dynamics. While only a few direct observations have been reported in the tropopause region, in this work the authors report very detailed observations of billow structures around 16-km altitude, in the upper part of the jet stream. Observations were made with very high frequency (VHF)-band mid-and upperatmosphere (MU) radar (Shigaraki, Japan; 34.85°N, 136.10°E) whose height resolution was improved with a range-imaging technique. KH billow structures were observed for at least 2 h and were found to have horizontal wavelengths of about 5.3 km and vertical extents between 0.5 and 1.0 km. Analysis of wind and temperature profiles measured by radiosondes launched from nearby meteorological stations indicated the presence of nearly monochromatic disturbances, likely due to a dominant inertia-gravity wave (IGW) superimposed on the background wind field. The presence of the IGW was also confirmed by analysis of wind profiles measured by the MU radar just before the KH billows were detected by the observations in range-imaging mode. The IGW, with vertical and horizontal wavelengths of about 3.5 and 600 km, respectively, may have been a direct radiation from the jet stream, as suggested by recent works, and likely played a major role in the onset of the observed KH instability.

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“…In astrophysical and geophysical fluid dynamics, high-Reynolds-number shear flows are often sharply stratified, i.e. they are stratified in such a manner that the vertical scale of density variation ℓ is much smaller than that of velocity shear, Λ [1][2][3][4][5]. In these circumstances, a key role in the flow development (in time and/or space) is played, as a rule, by Holmboe's instability [6] which attracts a considerable interest of researchers.…”

Section: Introductionmentioning

confidence: 99%

Weakly Nonlinear Stage of Instability Development in a Sharply Stratified Shear Flow with an Inflection-Free Velocity Profile

Churilov¹

2014

ujpa

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The distinctive property of the class of shear flows under study is that in a large part of the instability domain the phase velocities of waves are so close that their individual critical layers merge into a common one. Throughout a weakly nonlinear stage of perturbation development, this is the layer in that the most intensive and diverse wave interactions operate which determine scenario of perturbation evolution. Analysis of these interactions allows us, first, to reveal two stages of the evolution, three-wave one, when three-wave interactions dominate, and post-three-wave when numerous nonlinear interactions of different orders come into play, and, second, to determine which of the higher-order interactions are competitive. On this basis, we have found the structure of nonlinear evolution equations, substantiated that the nonlinear growth of wave amplitudes is explosive, and calculated growth indexes for both nonlinear stages. It is found that during the three-wave stage the most rapidly growing are low-frequency waves whereas at the next stage the growth of high-frequency waves is accelerated, and to the end of the weakly nonlinear stage all the waves have amplitudes of the same order. The results obtained are illustrated by numerical calculations for some ensembles of waves.

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Combined MU radar and ozonesonde measurements of turbulence and ozone fluxes in the tropo‐stratosphere over Shigaraki, Japan

Cited by 7 publications

References 25 publications

Stratified shear flow instabilities at large Richardson numbers

Stratified shear flow instabilities at large Richardson numbers

High-Resolution Observations with MU Radar of a KH Instability Triggered by an Inertia–Gravity Wave in the Upper Part of a Jet Stream

Weakly Nonlinear Stage of Instability Development in a Sharply Stratified Shear Flow with an Inflection-Free Velocity Profile

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