High-Frequency Gravity Waves and Kelvin-Helmholtz Billows in the Tropical UTLS, as Seen From Radar Observations of Vertical Wind - Département de mécanique
Article Dans Une Revue Geophysical Research Letters Année : 2024

High-Frequency Gravity Waves and Kelvin-Helmholtz Billows in the Tropical UTLS, as Seen From Radar Observations of Vertical Wind

Résumé

The present study analyzes novel observations of vertical wind (w) $(w)$ in the tropical upper troposphere-lower stratosphere obtained from a radar wind profiler in Cochin, India. Between December 2022 and April 2023, 63 consecutive 4 hr curtains of w $w$ were measured with a vertical spacing of 180 m and a sampling time step of 44 s, thus resolving almost the whole spectrum of vertical motions. Spectra of w $w$ strongly vary with altitude. They are generally flat up to the local Brunt-Väisälä frequency (BVF), but sometimes exhibit a peak of w $w$ variance closer to BVF, a feature which may be attributed to trapped gravity waves. At other times and locations, the w $w$ profiles reveal Kelvin-Helmholtz billows. Finally, the variability of w $w$ variance over the 4 month campaign period is investigated. Using brightness temperature from geostationary satellites as a convective proxy, it is found that w $w$ variance is highly correlated with fluctuations in convective activity.
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insu-04803004 , version 1 (25-11-2024)

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Ajil Kottayil, Aurélien Podglajen, Bernard Legras, Rachel Atlas, Prajwal K, et al.. High-Frequency Gravity Waves and Kelvin-Helmholtz Billows in the Tropical UTLS, as Seen From Radar Observations of Vertical Wind. Geophysical Research Letters, 2024, 51, pp.2024GL110366. ⟨10.1029/2024GL110366⟩. ⟨insu-04803004⟩
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