Ajil Kottayil, Aurélien Podglajen, Bernard Legras, Rachel Atlas, Prajwal K, K. Satheesan, Abhilash S
{"title":"High-Frequency Gravity Waves and Kelvin-Helmholtz Billows in the Tropical UTLS, as Seen From Radar Observations of Vertical Wind","authors":"Ajil Kottayil, Aurélien Podglajen, Bernard Legras, Rachel Atlas, Prajwal K, K. Satheesan, Abhilash S","doi":"10.1029/2024GL110366","DOIUrl":null,"url":null,"abstract":"<p>The present study analyzes novel observations of vertical wind <span></span><math>\n <semantics>\n <mrow>\n <mo>(</mo>\n <mi>w</mi>\n <mo>)</mo>\n </mrow>\n <annotation> $(w)$</annotation>\n </semantics></math> 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 <span></span><math>\n <semantics>\n <mrow>\n <mi>w</mi>\n </mrow>\n <annotation> $w$</annotation>\n </semantics></math> 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 <span></span><math>\n <semantics>\n <mrow>\n <mi>w</mi>\n </mrow>\n <annotation> $w$</annotation>\n </semantics></math> strongly vary with altitude. They are generally flat up to the local Brunt-Väisälä frequency (BVF), but sometimes exhibit a peak of <span></span><math>\n <semantics>\n <mrow>\n <mi>w</mi>\n </mrow>\n <annotation> $w$</annotation>\n </semantics></math> variance closer to BVF, a feature which may be attributed to trapped gravity waves. At other times and locations, the <span></span><math>\n <semantics>\n <mrow>\n <mi>w</mi>\n </mrow>\n <annotation> $w$</annotation>\n </semantics></math> profiles reveal Kelvin-Helmholtz billows. Finally, the variability of <span></span><math>\n <semantics>\n <mrow>\n <mi>w</mi>\n </mrow>\n <annotation> $w$</annotation>\n </semantics></math> variance over the 4 month campaign period is investigated. Using brightness temperature from geostationary satellites as a convective proxy, it is found that <span></span><math>\n <semantics>\n <mrow>\n <mi>w</mi>\n </mrow>\n <annotation> $w$</annotation>\n </semantics></math> variance is highly correlated with fluctuations in convective activity.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"51 21","pages":""},"PeriodicalIF":4.6000,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GL110366","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geophysical Research Letters","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2024GL110366","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The present study analyzes novel observations of vertical wind 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 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 strongly vary with altitude. They are generally flat up to the local Brunt-Väisälä frequency (BVF), but sometimes exhibit a peak of variance closer to BVF, a feature which may be attributed to trapped gravity waves. At other times and locations, the profiles reveal Kelvin-Helmholtz billows. Finally, the variability of variance over the 4 month campaign period is investigated. Using brightness temperature from geostationary satellites as a convective proxy, it is found that variance is highly correlated with fluctuations in convective activity.
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.