Observed generation of an atmospheric gravity wave by shear instability in the mean flow of the planetary boundary layer

Hooke, William H.; Hall, Freeman F.; Gossard, Earl E.

doi:10.1007/bf02188309

Cited by 65 publications

(31 citation statements)

References 11 publications

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“…Once triggered, gravity waves may amplify and eventually break, giving rise to mixing processes which augment turbulent fluxes occurring within the affected region (e.g., Nappo, 2002). Vertical shearing of the wind may also generate Kelvin-Helmholtz waves, both a direct source of turbulence, and a mechanism for gravity wave excitation (e.g., Hooke et al, 1973). Turbulence may be generated intermittently by the passage of a wave train or the cyclical generation of Kelvin-Helmholtz waves, resulting in a succession of such turbulent bursting episodes, although in the mean the ABL may appear stable (e.g., Kondo et al, 1978).…”

Section: Turbulent Heat Transfermentioning

confidence: 99%

Vertical Heat Transfer in the Lower Atmosphere over the Arctic Ocean During Clear-sky Periods

Mirocha

Kosović

2005

Boundary-Layer Meteorol

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Abstract. A diagnostic study of heat transfer within the lower atmosphere and between the atmosphere and the surface of the Arctic Ocean snow/ice pack during clear-sky conditions is conducted using data from the Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment. Surface heat budgets computed for four cloudy and four clear periods show that, while the net turbulent heat fluxes at the surface are small during the cloudy periods, during the clear-sky periods they are a considerable source of surface heating, balancing significant portions of the conductive heat fluxes from within the snow/ice pack. Analysis of the dynamics and thermodynamics of the lower atmosphere during the clear-sky periods reveals that a considerable portion of the heat lost to the surface by turbulent heat fluxes is balanced by locally strong heating near the atmospheric boundary-layer (ABL) top due to the interaction of subsiding motions with the strong overlying temperature inversions surmounting the ABL. This heat is then entrained into the ABL and transported to the surface by turbulent mixing, maintained by a combination of vertical wind shear and wave-turbulence interactions. The frequency of stable, clear-sky periods, particularly during the winter, combined with these results, suggests that the downward transfer of heat through the lower atmosphere and into the surface represents an important component of the heat budgets of the lower atmosphere and snow/ice pack over the annual cycle.

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Section: Turbulent Heat Transfermentioning

confidence: 99%

Vertical Heat Transfer in the Lower Atmosphere over the Arctic Ocean During Clear-sky Periods

Mirocha

Kosović

2005

Boundary-Layer Meteorol

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“…One challenge that must be encountered when conducting eddy-flux measurements in a stable boundary layer is the presence of wave-like disturbances (Nappo et al, 2008). Though the properties and propagation of wave-like disturbances in the boundary layer have been extensively studied (Chimonas, 1993(Chimonas, , 1999Finnigan, 1981, 1993;Einaudi et al, 1984;Finnigan and Einaudi, 1981;Hooke et al, 1973;Nappo, 2002), scant attention has been given to the impact of waves on turbulence and turbulent fluxes (Nappo et al, 2008;Viana et al, 2009;Zeri and Sa, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…Waves are ubiquitous in the nocturnal boundary layer (Gossard and Hooke, 1975;Grivet-Talocia et al, 1999;Nappo, 2002;Rees et al, 2000) and can be generated by a number of mechanisms, including thunderstorms (Gedzelman, 1983), orographic excitation (terrain induced) (Chimonas, 1993), and shear instability (Emmanuel, 1973;Hooke et al, 1973). Ducted waves are bound between the ground surface and some atmospheric reflecting layer above or two reflecting critical layers aloft (Cooper et al, 2006;Fritts et al, 2003;Newsom and Banta, 2003;Rees and Mobbs, 1988), thus producing a wave guide allowing propagation to occur over long distances and time periods.…”

Section: Introductionmentioning

confidence: 99%

On the impact of wave-like disturbances on turbulent fluxes and turbulence statistics in nighttime conditions: a case study

Durden

Nappo²,

Leclerc

et al. 2013

Biogeosciences

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Abstract. The interpretation of flux measurements in nocturnal conditions is typically fraught with challenges. This paper reports on how the presence of wave-like disturbances in a time series, can lead to an overestimation of turbulence statistics, errors when calculating the stability parameter, erroneous estimation of the friction velocity u * used to screen flux data, and errors in turbulent flux calculations. Using time series of the pressure signal from a microbarograph, wavelike disturbances at an AmeriFlux site are identified. The wave-like disturbances are removed during the calculation of turbulence statistics and turbulent fluxes. Our findings suggest that filtering eddy-covariance data in the presence of wave-like events prevents both an overestimation of turbulence statistics and errors in turbulent flux calculations. Results show that large-amplitude wave-like events, events surpassing three standard deviations, occurred on 18 % of the nights considered in the present study. Remarkably, on flux towers located in a very stably stratified boundary-layer regime, the presence of a gravity wave can enhance turbulence statistics more than 50 %. In addition, the presence of the disturbance modulates the calculated turbulent fluxes of CO 2 resulting in erroneous turbulent flux calculations of the order of 10 % depending on averaging time and pressure perturbation threshold criteria. Furthermore, the friction velocity u * was affected by the presence of the wave, and in at least one case, a 10 % increase caused u * to exceed the arbitrary 0.25 m s −1 threshold used in many studies. This results in an unintended bias in the data selected for analysis in the flux calculations. The impact of different averaging periods was also examined and found to be variable specific. These early case study results provide an insight into errors introduced when calculating "purely" turbulent fluxes. These results could contribute to improving modeling efforts by providing more accurate inputs of both turbulent kinetic energy, and isolating the turbulent component of u * for flux selection in the stable nocturnal boundary layer.

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“…of wave generation by shear instability in the boundary-layer shear flow. This particular event is discussed in detail by Hooke et al (1973).…”

Section: Sounder and Microbarograph Recordsmentioning

confidence: 97%

“…In the one event studied in detail so far (Figure 10), we have determined that the wave phase velocity is indeed equal to the wind velocity in the middle of the shear zone, as assumed by Emmanuel and his co-workers in their analyses, and we have measured a rather considerable vertical energy flux, ~800 erg cm -z s -1. The results are discussed in more detail in a separate paper (Hooke et al, 1973). Acoustic echo-sounder facsimile record showing the breaking wave structure characteristic Fig.…”

Section: Sounder and Microbarograph Recordsmentioning

confidence: 98%

Acoustic echo-sounding techniques and their application to gravity-wave, turbulence, and stability studies

Beran

Hooke

Clifford

1973

Boundary-Layer Meteorol

Self Cite

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Abstract. This paper is a brief summary of recent experimental studies conducted by the WPL staff in order to: (a) compare acoustic echo strengths with those predicted from measured turbulence intensities and scatter theory; (b) develop optimum experimental geometries for Doppler work, and (c) use the acoustic echo-sounder as a quantitative tool in studies of gravity wave dynamics in, and immediately above, the stable planetary boundary layer. We find that the observed acoustic echo strengths are roughly an order of magnitude greater than those predicted theoretically. This discrepancy might be in part due to partial reflection although the comparison is somewhat clouded by uncertainties in our knowledge of the equipment characteristics, propagation losses, etc. Comparisons between Doppler and in situ wind measurements give confidence in the Doppler results, but further experimentation and comparisons are needed. Preliminary use of acoustic Doppler data in a case study of gravity-wave dynamics in the planetary boundary layer has yielded boundary-layer wind speed and direction profiles which give insight into the mechanisms responsible for the wave generation. The Doppler data yield estimates of the wave associated momentum fluxes (~ a few dyn cm -z) as well. The results derived from the acoustic techniques are quite encouraging, but thus far remain unsubstantiated by independent wind and flux measurements.

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Observed generation of an atmospheric gravity wave by shear instability in the mean flow of the planetary boundary layer

Cited by 65 publications

References 11 publications

Vertical Heat Transfer in the Lower Atmosphere over the Arctic Ocean During Clear-sky Periods

Vertical Heat Transfer in the Lower Atmosphere over the Arctic Ocean During Clear-sky Periods

On the impact of wave-like disturbances on turbulent fluxes and turbulence statistics in nighttime conditions: a case study

Acoustic echo-sounding techniques and their application to gravity-wave, turbulence, and stability studies

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