Air motion within Kelvin-Helmholtz billows determined from simultaneous Doppler radar and aircraft measurements

Browning, K. A.; BRYANT, GW; STARR, JR; AXFORD, DN

doi:10.1256/smsqj.42202

Cited by 12 publications

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“…They concluded that only a small enhancement of the wind shear at the interface will reduce Ri to the critical value required to trigger the KHI, and the breaking of KH waves result in the enhanced turbulence. Browning and Watkins [1970] and Browning et al [1973] describes the detection of KH billows in the upper troposphere using a high-power radar. The billows were detected in clear air and every occurrence of billows was found to be closely associated with well-defined, local, wind-shear maxima.…”

Section: Discussionmentioning

confidence: 99%

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First observations of turbulence parameters in the troposphere over the Bay of Bengal and the Arabian Sea using radiosonde

Alappattu¹,

Kunhikrishnan²

2010

J. Geophys. Res.

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[1] This paper discusses the turbulence characteristics of the free atmosphere over the Bay of Bengal and the Arabian Sea during the premonsoon season of 2006. The turbulence scaling concepts, developed over the past decades for application to oceanic mixing, are used for retrieving turbulence properties in the free atmosphere from high-resolution soundings, as described by Clayson and Kantha (2008). The variability in the vertical turbulence structure over a large spatial region is studied using this novel method for the first time. Investigations revealed the presence of a highly turbulent band at upper troposphere below the cold point tropopause (CPT) with significant enhancements in Thorpe length and eddy diffusion coefficient. This increased turbulence is studied in conjunction with the observations of the tropical tropopause layer (TTL). It is seen that the lower and upper boundaries of this turbulence band nearly coincide with the height where the potential temperature lapse rate begins to show a decrease (LRH min ) and cold point tropopause, respectively. The TTL is the transition regime from convectively dominated troposphere to radiatively dominated stratosphere, and is characterized by a decrease in the static stability. The enhanced zonal and meridional wind shear observed in this region shows that the stability in this region is further weakened because of the breaking of Kelvin-Helmholtz waves, which results in the enhancement of turbulence. The study reveals the potential of high-resolution soundings to be used in the investigations of turbulence in the free atmosphere.

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Section: Discussionmentioning

confidence: 99%

“…The minimum value of the Richardson number when evaluated over layers of 200 m depth was usually found to be in the range of 0.15 -0.3. However, any clearly defined relationship between the billows and static stability was not found [Browning et al, 1973].…”

Section: Discussionmentioning

confidence: 99%

First observations of turbulence parameters in the troposphere over the Bay of Bengal and the Arabian Sea using radiosonde

Alappattu¹,

Kunhikrishnan²

2010

J. Geophys. Res.

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“…Also evident are small-scale temperature fluctuations with a horizontal ground-based wavelength of approximately 1 km (e.g., at 50 km flight distance). These are likely to be a signature of Kelvin-Helmholtz billows appearing during the transition to turbulent flow [Browning et al, 1973]. It is interesting to note that these small-scale waves exhibit a striking sawtooth waveform on closer inspection.…”

Section: Horizontal Flight Legmentioning

confidence: 93%

Airborne observations of turbulence, mixing, and gravity waves in the tropopause region

et al. 2002

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[1] In situ observations of small-scale dynamics and compositional structure in the tropopause region are presented. The measurements were made aboard the Grob ''Egrett'' high-altitude research aircraft above Aberystwyth, Wales, in the summer of 2000. The observations presented here show evidence of mixing of ozone and water vapor in a patch of intense turbulence just above the tropopause. This turbulence is shown to be the result of wind shear above a tropospheric jet stream. The value of the vertical eddy diffusion coefficient in this turbulence is estimated to be 0.9 m 2 s À1 . It is also shown that wavelike perturbations superimposed on the overall tracer structure can be accounted for by a gravity wave.

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“…Shear structures Chapman and Browning (1997) showed that the shear within large-amplitude billows that were clearly visible in the Doppler returns from frontal precipitation had a cat's-eye structure that was similar to the clear-air reflectivity patterns observed by, for example, Browning (1971). Fig.…”

Section: A Validation Of Streamlinesmentioning

confidence: 60%

“…The few known to the authors have all been related to observations of Kelvin-Helmholtz (KH) billows. Starr and Browning (1972) showed the nu-merical values of the vertical shear calculated over height increments of 200 m within billows that had a crest-trough amplitude of around 600 m. Browning et al (1973a) showed the vertical shear calculated over height increments of 100 m through billows that had a crest-trough amplitude of between 230 and 450 m. Although both these studies showed that the shear had maxima in the billows themselves, the resolution of the measurements (compared to the amplitude of the billows) was insufficient to resolve details in the patterns of shear. Recently Chapman and Browning (1997) showed the shear calculated over height increments much smaller than the amplitude of the billows through which the measurements were made.…”

Section: Introductionmentioning

confidence: 99%

Use of Wind-Shear Displays for Doppler Radar Data

Chapman¹,

Browning²

1998

Bull. Amer. Meteor. Soc.

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Air motion within Kelvin-Helmholtz billows determined from simultaneous Doppler radar and aircraft measurements

Cited by 12 publications

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First observations of turbulence parameters in the troposphere over the Bay of Bengal and the Arabian Sea using radiosonde

First observations of turbulence parameters in the troposphere over the Bay of Bengal and the Arabian Sea using radiosonde

Airborne observations of turbulence, mixing, and gravity waves in the tropopause region

Use of Wind-Shear Displays for Doppler Radar Data

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