A direct aircraft observation of helical rolls in the tropical cyclone boundary layer

Helical rolls are known to play a significant role in modulating both the mean and turbulence structure of the atmospheric boundary layer in tropical cyclones. However, in-situ measurements of these rolls have been limited due to safety restrictions. This study presents analyses of data collected by...

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Bibliographic Details
Published in:Scientific reports 2021-09, Vol.11 (1), p.18771-18771, Article 18771
Main Authors: Tang, Jie, Zhang, Jun A., Chan, Pakwai, Hon, Kaikwong, Lei, Xiaotu, Wang, Yuan
Format: Article
Language:English
Subjects:
639/766/189
704/106/35/823
Aircraft
Atmospheric boundary layer
Atmospheric turbulence
Boundary layers
Cyclones
Flight
Humanities and Social Sciences
Hurricanes
Mathematical models
multidisciplinary
Science
Science (multidisciplinary)
Tropical cyclones
Typhoons
Wind speed
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Summary:Helical rolls are known to play a significant role in modulating both the mean and turbulence structure of the atmospheric boundary layer in tropical cyclones. However, in-situ measurements of these rolls have been limited due to safety restrictions. This study presents analyses of data collected by an aircraft operated by the Hong Kong Observatory in Typhoon Kalmaegi (1415) and Typhoon Nida (1604). Examination of the flight-level data at ~ 600 m altitude confirmed the existence of sub-kilometer-scale rolls. These rolls were mostly observed in the outer-core region. Turbulent momentum fluxes were computed using the eddy correlation method. The averaged momentum flux of flight legs with rolls was found to be ~ 2.5 times that of legs without rolls at a similar wind speed range. This result suggests that rolls could significantly modulate turbulent transfer in the tropical cyclone boundary layer. This roll effect on turbulent fluxes should be considered in the planetary boundary layer parameterization schemes of numerical models simulating and forecasting tropical cyclones.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-021-97766-7