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Kelvin-Helmholtz Billows in the Troposphere and Lower Stratosphere Detected by the PANSY Radar
  • Yuichi Minamihara,
  • Kaoru Sato,
  • Masaki Tutumi
Yuichi Minamihara
University of Tokyo

Corresponding Author:minamihara@eps.s.u-tokyo.ac.jp

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Kaoru Sato
University of Tokyo
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Masaki Tutumi
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We conducted two 10-day observational campaigns in 2019 targeting turbulence in the troposphere and lower stratosphere by adopting a frequency domain radar interferometric imaging technique using Program of the Antarctic Syowa (PANSY) radar and radiosonde observations obtained at Syowa Station in the Antarctic. Overall, 73 cases of Kelvin-Helmholtz (K-H) billows were detected, and 2 characteristic cases were examined in detail. In the first case with the longest duration of ~6.5 h, the K-H billows had thickness of ~800 m and horizontal wavelength of ~2500 m. According to a numerical simulation of the environmental conditions, continuously existing orographic gravity waves maintained strong vertical shear of the horizontal winds sufficient to cause the K-H instability. In the second case with the deepest thickness of ~1600m, the K-H billows had duration of ~1.5 h and horizontal wavelength of ~4320m. Numerical simulation suggested that an enhanced upper-tropospheric jet associated with a well-developed synoptic-scale cyclone caused the K-H instability. Such background conditions, frequently observed in the Antarctic coastal region, are typical mechanisms for K-H excitation. Linear stability analysis also indicated that the characteristics of the observed K-H billows were consistent with the most unstable modes. Furthermore, statical analysis was performed using data of all 73 observed cases. The characteristics of K-H billows observed at Syowa Station are similar to those observed over Japan. However, the weaker vertical shear and longer wave period of the K-H billows over Syowa Station reflect that the tropospheric jet over the Antarctica is not as strong as that over Japan.