Gravity-wave breaking: Linear and primary nonlinear dynamics

Achatz, Ulrich

doi:10.1016/j.asr.2007.03.078

Cited by 34 publications

(35 citation statements)

References 66 publications

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“…However, many experimental and theoretical studies reveal a more complicated and not a straightforward relation between turbulent flow and Ri c (e.g. Achatz, 2007;Balsley et al, 2008;Haack et al, 2014).…”

Section: Derivation Of ε From Radiosonde Datamentioning

confidence: 99%

“…Convectively generated gravity waves and gravity wave breaking are also important causes responsible for turbulence generation (e.g. Lindzen, 1981;Achatz, 2007). Furthermore, the remaining well-known generation mechanisms of turbulence include strong wind shears associated with jet streams and upper-level fronts, wave-wave interaction, mountain waves, convective clouds, and thunderstorms (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Derivation of turbulent energy dissipation rate with the Middle Atmosphere Alomar Radar System (MAARSY) and radiosondes at Andøya, Norway

Rapp

Schrön

et al. 2016

Ann. Geophys.

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Abstract. We present the derivation of turbulent energy dissipation rate ε from a total of 522 days of observations with the Middle Atmosphere Alomar Radar SYstem (MAARSY) mesosphere-stratosphere-troposphere (MST) radar running tropospheric experiments during the period of 2010-2013 as well as with balloon-borne radiosondes based on a campaign in the summer 2013. Spectral widths are converted to ε after the removal of the broadening effects due to the finite beam width of the radar. With the simultaneous in situ measurements of ε with balloon-borne radiosondes at the MAARSY radar site, we compare the ε values derived from both techniques and reach an encouraging agreement between them. Using all the radar data available, we present a preliminary climatology of atmospheric turbulence in the UTLS (upper troposphere and lower stratosphere) region above the MAARSY site showing a variability of more than 5 orders of magnitude inherent in turbulent energy dissipation rates. The derived ε values reveal a log-normal distribution with a negative skewness, and the ε profiles show an increase with height which is also the case for each individual month. Atmospheric turbulence based on our radar measurements reveals a seasonal variation but no clear diurnal variation in the UTLS region. Comparison of ε with the gradient Richardson number Ri shows that only 1.7 % of all the data with turbulence occur under the condition of Ri < 1 and that the values of ε under the condition of Ri < 1 are significantly larger than those under Ri > 1. Further, there is a roughly negative correlation between ε and Ri that is independent of the scale dependence of Ri. Turbulence under active dynamical conditions (velocity of horizontal wind U > 10 m s −1 ) is significantly stronger than under quiet conditions (U < 10 m s −1 ). Last but not least, the derived ε values are compared with the corresponding vertical shears of background wind velocity showing a linear relation with a corresponding correlation coefficient r = 58 % well above the 99.9 % significance level. This implies that wind shears play an important role in the turbulence generation in the troposphere and lower stratosphere (through the Kelvin-Helmholtz instability).

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Section: Derivation Of ε From Radiosonde Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Derivation of turbulent energy dissipation rate with the Middle Atmosphere Alomar Radar System (MAARSY) and radiosondes at Andøya, Norway

Rapp

Schrön

et al. 2016

Ann. Geophys.

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show abstract

“…Figure 4 indicates the lowest value Ri ∼ 0.10 near 87 km for both flights, and other regions having low values between 0.25 and 1.0 are near 90-94 km, and 97-106 km. In addition, horizontal gradients will also contribute to flow instability and gravity waves may become unstable for Ri > 0.25 (e.g., Achatz, 2007).…”

Section: Stabilitymentioning

confidence: 99%

The Turbopause experiment: atmospheric stability and turbulent structure spanning the turbopause altitude

et al. 2011

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Abstract. Very few sequences of high resolution wind and temperature measurements in the lower thermosphere are available in the literature, which makes it difficult to verify the simulation results of models that would provide better understanding of the complex dynamics of the region. To address this problem the Turbopause experiment used four rockets launched over a period of approximately two hours from Poker Flat Research Range, Alaska (64 • N, 147 • W) on the night of 17-18 February 2009. All four rocket payloads released trimethyl aluminum trails for neutral wind and turbulence measurements, and two of the rockets carried ionization gauges and fixed-bias Langmuir probes measuring neutral and electron densities, small-scale fluctuations and neutral temperatures. Two lidars monitored temperature structure and sodium densities. The observations were made under quiet geomagnetic conditions and show persistence in the wind magnitudes and shears throughout the observing period while being modulated by inertia-gravity waves. High resolution temperature profiles show the winter polar mesosphere and lower thermosphere in a state of relatively low stability with several quasi-adiabatic layers between 74 and 103 km. Temperature and wind data were combined to calculate Richardson number profiles. Evidence for turbulence comes from simultaneous observations of density fluctuations and downward transport of sodium in a mixed layer near 75 km; the observation of turbulent fluctuations and energy dissipation from 87-90 km; and fast and irregular trail expansion at 90-93 km, and especially between 95 to 103 km. The regions of turbulent trails agree well with regions of quasi-adiabatic temperature gradients. Above Correspondence to: G. A. Lehmacher (glehmac@clemson.edu) 103 km, trail diffusion was mainly laminar; however, unusual features and vortices in the trail diffusion were observed up to 118 km that have not been as prevalent or as clearly evident in earlier trail releases.

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“…turbulence is generated, until the wave amplitude attains the threshold value, resulting in a Richardson number profile with several patches very close to the threshold (i.e. Ri ≈ 0.25, although note that Achatz (2007) found that turbulence can be produced by gravity waves in a flow with Ri values over 0.25). The breaking of these high-amplitude waves produces momentum flux divergences that persist for a period of three days at least, and therefore may produce large influences on the general circulation.…”

Section: Discussionmentioning

confidence: 99%

High gravity‐wave activity observed in Patagonia, Southern America: generation by a cyclone passage over the Andes mountain range

Pulido

Rodas

Dechat

et al. 2012

Quart J Royal Meteoro Soc

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Gravity-wave breaking: Linear and primary nonlinear dynamics

Cited by 34 publications

References 66 publications

Derivation of turbulent energy dissipation rate with the Middle Atmosphere Alomar Radar System (MAARSY) and radiosondes at Andøya, Norway

Derivation of turbulent energy dissipation rate with the Middle Atmosphere Alomar Radar System (MAARSY) and radiosondes at Andøya, Norway

The Turbopause experiment: atmospheric stability and turbulent structure spanning the turbopause altitude

High gravity‐wave activity observed in Patagonia, Southern America: generation by a cyclone passage over the Andes mountain range

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