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

IF 4.6 1区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Geophysical Research Letters Pub Date : 2024-11-08 DOI:10.1029/2024GL110366
Ajil Kottayil, Aurélien Podglajen, Bernard Legras, Rachel Atlas, Prajwal K, K. Satheesan, Abhilash S
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Abstract

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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从雷达垂直风观测数据看热带UTLS的高频重力波和开尔文-赫姆霍兹气流
本研究分析了从印度科钦的雷达风廓线仪获得的热带对流层上部-平流层下部垂直风(w)$(w)$的新观测数据。在 2022 年 12 月至 2023 年 4 月期间,以 180 米的垂直间距和 44 秒的采样时间步长测量了 63 个连续 4 小时的 w$w$ 窗帘,从而解析了几乎整个垂直运动频谱。w$w$ 的频谱随高度变化很大。一般来说,直到当地的布伦特-韦赛莱频率(BVF)都是平的,但有时会在更接近布伦特-韦赛莱频率的地方出现 w$w$ 方差峰值,这可能是受困重力波造成的。在其他时间和地点,w$w$剖面显示出开尔文-赫尔姆霍兹波浪。最后,研究了 w$w$ 方差在 4 个月活动期间的变化情况。利用地球静止卫星的亮度温度作为对流的代用指标,发现 w$w$ 方差与对流活动的波动高度相关。
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来源期刊
Geophysical Research Letters
Geophysical Research Letters 地学-地球科学综合
CiteScore
9.00
自引率
9.60%
发文量
1588
审稿时长
2.2 months
期刊介绍: Geophysical Research Letters (GRL) publishes high-impact, innovative, and timely research on major scientific advances in all the major geoscience disciplines. Papers are communications-length articles and should have broad and immediate implications in their discipline or across the geosciences. GRLmaintains the fastest turn-around of all high-impact publications in the geosciences and works closely with authors to ensure broad visibility of top papers.
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