An Investigation of a Kelvin-Helmholtz Billow Cloud

Reiss, Nathan M.; Corona, T.J.

doi:10.1175/1520-0477(1977)058<0159:aioakh>2.0.co;2

Cited by 6 publications

(4 citation statements)

References 6 publications

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“…Initially studied and documented by fluid dynamicists Helmholtz (1868) and Lord Kelvin (1871), later studies were done using both visual (Ludlam 1967;Reiss and Corona 1977) and laboratory observations (Drazin 1958;Thorpe 1968Thorpe , 1971Thorpe , 1973Simpson 1969Simpson , 1982Scotti and Corcos 1972;Britter and Simpson 1978;Koop and Browand 1979). As technology advanced, K-H waves were also observed by an assortment of instrumentation including ground-based radars (Hicks and Angell 1968;Browning and Watkins 1970;Mueller and Carbone 1987;Weckwerth and Wakimoto 1992;Chapman and Browning 1997;Petre and Verlinde 2004;Luce et al 2008) and airborne radars equipped with additional instrumentation (Browning et al 1973, Hardy et al 1973Wakimoto et al 1992;Wakimoto and Bosart 2001;Friedrich et al 2008;Geerts and Miao 2010), and were numerically simulated (Fritts 1979;Sykes and Lewellen 1982;Droegemeier and Wilhelmson 1986;Fritts et al 1996).…”

Section: Introductionmentioning

confidence: 99%

Polarimetric Doppler Radar Observations of Kelvin–Helmholtz Waves in a Winter Storm

Houser

Bluestein

2011

Journal of the Atmospheric Sciences

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Kelvin-Helmholtz waves were observed by the Twin Lakes, Oklahoma (KTLX), Weather Surveillance Radar-1988 Doppler (WSR-88D); the Norman, Oklahoma (KOUN), polarimetric WSR-88D; and the polarimetric Collaborative Adaptive Sensing of the Atmosphere (CASA) radars on 30 November 2006 during a winter storm in central Oklahoma. The life cycle and structure of the waves are analyzed from the radar data, and the nearby atmospheric conditions are examined. The initial perturbations associated with the waves are first evident only in the radars' radial velocity fields. As the waves mature, perturbations become discernable in the reflectivity factor Z and spectrum width (SW) fields of both radars, and in the differential reflectivity Z dr and, to a lesser extent, the cross-correlation coefficient r hv fields of KOUN. As the waves break and begin to dissipate, the perturbations subside.A dual-Doppler analysis is synthesized to examine the kinematic structure of the waves and to relate the polarimetric observations to the kinematics. It is determined that Z and Z dr are enhanced in regions of upward motion (wave crests), and r hv is reduced in the same vicinity and near the base of the wave circulations. Vertical velocity perturbations transport horizontal momentum upward and downward, inducing horizontal wind perturbations that are approximately 908 out of phase and downstream from their corresponding vertical velocity perturbations. Perturbations in Z, Z dr , and r hv are observed in the vicinity of wave crests while SW perturbations occur predominately in and just upstream from wave troughs. It is determined that perturbations in the polarimetric variables are a result of the waves modifying local precipitation microphysics. Perturbations in Z and Z dr are hypothesized to be the result of columnar ice crystal generation whereas those in r hv likely result from the mixing of ice crystals of various shapes and sizes. Perturbations in SW are a result of turbulent motions likely associated with wave breaking and downward advection of a strong shear layer.

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Section: Introductionmentioning

confidence: 99%

Polarimetric Doppler Radar Observations of Kelvin–Helmholtz Waves in a Winter Storm

Houser

Bluestein

2011

Journal of the Atmospheric Sciences

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“…Because KH instabilities are often associated with turbulence or gravity waves, they can also have some impacts within clouds [e.g., Ludlam , 1967; Reiss and Corona , 1977; Demoz et al , 1998; Sassen et al , 2003, Wada et al , 2005]. In particular, they can affect the formation, maintenance, and dissipation of cirrus clouds [ Smith and Jonas , 1996; Quante and Starr , 2002].…”

Section: Introductionmentioning

confidence: 99%

Observations of Kelvin‐Helmholtz instability at a cloud base with the middle and upper atmosphere (MU) and weather radars

et al. 2010

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[1] Using the very high frequency (46.5 MHz) middle and upper atmosphere radar (MUR), Ka band (35 GHz) and X band (9.8 GHz) weather radars, a Kelvin-Helmholtz (KH) instability occurring at a cloud base and its impact on modulating cloud bottom altitudes are described by a case study on 8 October 2008 at the Shigaraki MU Observatory, Japan (34.85°N, 136.10°E). KH braids were monitored by the MUR along the slope of a cloud base gradually rising with time around an altitude of ∼5.0 km. The KH braids had a horizontal wavelength of about 3.6 km and maximum crest-to-trough amplitude of about 1.6 km. Nearly monochromatic and out of phase vertical air motion oscillations exceeding ±3 m s −1 with a period of ∼3 min 20 s were measured by the MUR above and below the cloud base. The axes of the billows were at right angles of the wind and wind shear both oriented east-north-east at their altitude. The isotropy of the radar echoes and the large variance of Doppler velocity in the KH billows (including the braids) indicate the presence of strong turbulence at the Bragg (∼3.2 m) scale. After the passage of the cloud system, the KH waves rapidly damped and the vertical scale of the KH braids progressively decreased down to about 100 m before their disappearance. The radar observations suggest that the interface between clear air and cloud was conducive to the presence of the dynamical shear instability by reducing static stability (and then the Richardson number) near the cloud base. Downward cloudy protuberances detected by the Ka band radar had vertical and horizontal scales of about 0.6-1.1 and 3.2 km, respectively, and were clearly associated with the downward air motions. Observed oscillations of the reflectivity-weighted Doppler velocity measured by the X band radar indicate that falling ice particles underwent the vertical wind motions generated by the KH instability to form the protuberances. The protuberances at the cloud base might be either KH billow clouds or perhaps some sort of mamma. Reflectivity-weighted particle fall velocity computed from Doppler velocities measured by the X band radar and the MUR showed an average value of 1.3 ms −1 within the cloud and in the protuberance environment.

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“…Dutton (1971) proposed that the cause of turbulence is due to Kelvin-Helmholtz (K-H) instability, which is a hydrodynamic instability produced by a strong vertical wind shear of horizontal winds under a weak density stratification. K-H billows have often been observed in the middle and upper troposphere (e.g., Ludlam 1967;Atlas et al 1970;Browning and Watkins 1970;Dutton and Panofsky 1970;Browning 1971;Reiss and Corona 1977;Petre and Verlinde 2004;Luce et al 2010;Conrick et al 2018;Barnes et al 2018;Luce et al 2018;Grasmick and Geerts 2020) and in the planetary boundary layer (e.g., Blumen et al 2001). The K-H billows, observed by Luce et al (2018), were characterized by couplets of upward and downward velocities with the width of 3.7 km around an altitude of 6.5 km, which lasted for about 20 min.…”

Section: Introductionmentioning

confidence: 98%

Statistical Analysis of Aviation Turbulence in the Middle–Upper Troposphere over Japan

Miyamoto

Matsumoto²,

Ito

2023

Journal of Applied Meteorology and Climatology

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This study examined the statistics of aviation turbulence that occurred in Japan between 2006 and 2018 by analyzing the Pilot Report (PIREP). In total, 81,639 turbulence events, with moderate or greater intensity, were reported over this period. The monthly number of turbulence cases has an annual periodical variation as observed in different regions by previous studies. The number of turbulence cases is high from March to June and low in July and August. Higher number of turbulence cases are experienced along the major flight routes in Japan, especially around Tokyo, for the active period between 9:00 and 20:00 local time. The number of cases of turbulence peaks when the flight reaches an altitude of 33000 ft (FL330), while it reduces when the flight altitude is above FL380 and below FL280. The statistical features are not largely different among the four seasons; however, there are some exceptions. For instance, the number of turbulence cases is large in high altitudes in summer and small in low altitudes in winter. Considering the number of flights, it is evident that the frequency of turbulence is higher in altitudes between FL200 and FL350, although the number of flights is low in this altitude region. The number of convectively induced turbulence is relatively large during the daytime in summer compared with the other seasons. Large number of mountain wave turbulence is observed around the mountainous region in fall and winter when the jet stream flows over Japan.

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An Investigation of a Kelvin-Helmholtz Billow Cloud

Cited by 6 publications

References 6 publications

Polarimetric Doppler Radar Observations of Kelvin–Helmholtz Waves in a Winter Storm

Polarimetric Doppler Radar Observations of Kelvin–Helmholtz Waves in a Winter Storm

Observations of Kelvin‐Helmholtz instability at a cloud base with the middle and upper atmosphere (MU) and weather radars

Statistical Analysis of Aviation Turbulence in the Middle–Upper Troposphere over Japan

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