Detection of Kelvin‐Helmholtz instability with the Indian mesosphere‐stratosphere‐troposphere radar: A case study

Singh, Sachchidanand; Mahajan, K. K.; Choudhary, R. K.; Nagpal, O. P.

doi:10.1029/98jd02675

Cited by 10 publications

(19 citation statements)

References 26 publications

(27 reference statements)

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“…As expected, N 2 is found to be high at that height level (13.25 km), the shear is high at 12.85 km and corresponding R i is found to be below its critical value (0.25). It is also observed that the vertical velocities reverse direction at that critical height (Singh et al, 1999). This suggests that the power bursts patterns are associated with the KHI.…”

Section: Tilting Of Atmospheric Layers and Their Generation Mechanismsmentioning

confidence: 53%

“…After 17:15 IST, the power burst patterns are observed to be slowly disappearing and coming downward to about 12 km. Such power burst patterns are the typical signature of KHI (Klostermeyer and Ruster, 1980;Singh et al, 1999). To confirm the same, data from GPS sonde launched at 16:30 h (marked in Fig.…”

Section: Tilting Of Atmospheric Layers and Their Generation Mechanismsmentioning

confidence: 97%

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Aspect sensitivity in the VHF radar backscatters studied using simultaneous observations of Gadanki MST radar and GPS sonde

et al. 2004

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Abstract. Simultaneous observations made on four days using the MST radar and GPS-sonde at Gadanki (13.5 • N, 79.2 • E), a tropical station in India, are presented to address the aspect sensitivity of radar backscatters observed at different heights. The observations show that wherever stability parameter N 2 is high, vertical shear of horizontal wind is low and Richardson number (R i ) is high, the aspect sensitivity is high indicating that the aspect sensitive radar backscatters are due to thermal structures in the atmosphere. Such a case can be seen very clearly in the upper troposphere and lower stratosphere. At some heights, where N 2 is high, R i is high, but shears are relatively weak, the aspect sensitivity is found to almost disappear, indicating that some amount of shear provides favorable conditions for causing aspect sensitivity. Aspect sensitivity does not occur at all where N 2 is low or negative and R i is low in spite of wind shear being either high or low, indicating that the regions are well mixed and hence turbulent. The study also shows a power difference in the symmetric beams. A case study on this aspect suggests that this asymmetry is due to the tilting of layers by the action of atmospheric waves. There is indication that these waves are generated through Kelvin-Helmholtz-instability (KHI).

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Section: Tilting Of Atmospheric Layers and Their Generation Mechanismsmentioning

confidence: 53%

Section: Tilting Of Atmospheric Layers and Their Generation Mechanismsmentioning

confidence: 97%

Aspect sensitivity in the VHF radar backscatters studied using simultaneous observations of Gadanki MST radar and GPS sonde

et al. 2004

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“…It occurs at the critical level of KH instability generation. In fact, the V air pattern exhibits a much more complex structure than a simple attenuation of V air around the critical layer (around the altitude of 5.0 km where a phase shift of V air occurs) as shown by Klostermeyer and Rüster [1980] or Singh et al [1999], for example. The V air pattern in Figure 5 rather presents a striking resemblance with the very high resolution height‐time (30 m, 3 s) cross section of vertical wind velocities due a KH instability measured by a 95 GHz cloud radar [ Petre and Verlinde , 2004].…”

Section: Resultsmentioning

confidence: 99%

“…Mesosphere‐stratosphere‐troposphere (MST) radars can also be used for studying KH instabilities in the atmosphere [e.g., Röttger and Schmidt , 1979; VanZandt et al , 1979; Klostermeyer and Rüster , 1980, 1981; Singh et al , 1999; Yamamoto et al , 2003; Kelley et al , 2005]. The development of frequency domain interferometry (FDI) techniques (using two carrier frequencies or more and devoted to improve the range resolution of the MST radars) allowed direct observations of KH billows [e.g., Chilson et al , 1997, 2003; Luce et al , 2007, 2008].…”

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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“…Asymmetry often continues to 10 000 m scale, which is more than typical KHI wavelengths, but could be caused in line-fitting of smaller scale ramp structures. VHF echo power varies in KHI (Klostermeyer and Ru¨ster, 1981;Chilson et al, 1997;Singh et al, 1999); however, tilted y structures could often be within the radar time resolution and sampling volume, e.g. Muschinski (2004).…”

Section: Article In Pressmentioning

confidence: 99%

Aircraft measurements of asymmetric temperature microstructure causing azimuth variations of VHF radar echo power

Worthington¹

2007

Journal of Atmospheric and Solar-Terrestrial Physics

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Detection of Kelvin‐Helmholtz instability with the Indian mesosphere‐stratosphere‐troposphere radar: A case study

Cited by 10 publications

References 26 publications

Aspect sensitivity in the VHF radar backscatters studied using simultaneous observations of Gadanki MST radar and GPS sonde

Aspect sensitivity in the VHF radar backscatters studied using simultaneous observations of Gadanki MST radar and GPS sonde

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

Aircraft measurements of asymmetric temperature microstructure causing azimuth variations of VHF radar echo power

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