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DOI	10.1016/j.atmosres.2020.105298
	On the distribution of helicity in the tropical cyclone boundary layer from dropsonde composites
	Chen N.; Tang J.; Zhang J.A.; Ma L.-M.; Yu H.
发表日期	2021
ISSN	0169-8095
卷号	249
英文摘要	This study analyzes GPS dropsonde data in multiple tropical cyclones from 1997 to 2017 to investigate the boundary layer structure with a focus on helicity distribution. A helicity-based method for boundary layer height is developed and evaluated by comparing it to other boundary layer height scales including the inflow layer depth, height of the maximum tangential wind speed and thermodynamic mixed layer depth. Our dropsonde composites confirmed the radial variations of these boundary layer heights seen in previous studies. The results show that the boundary layer height defined by the maximum vertical gradient of helicity is closest to the height of the maximum tangential wind speed or jet height and is located between the inflow layer depth and thermodynamic mixed layer height in all intensity groups. All three kinematic height scales generally decrease with storm intensity at a given radius. These kinematic height scales converge in the major hurricane group, while the inflow layer depth is much larger than the other two height scales in the tropical storm group. The maximum normalized helicity is located at 100–200 m altitude which is close to the height of the maximum inflow. Both front-back and downshear-upshear asymmetries are observed in the 0–1 km layer integrated helicity in the inner core region of a storm, and the helicity on the front and downshear sides is larger in all intensity groups. The results also show that the helicity magnitude is generally larger in the boundary layer of stronger storms. Application of helicity to quantify turbulent characteristics in the boundary layer is discussed. © 2020
英文关键词	Boundary layer; Dropsonde composite; Helicity; Tropical cyclone
语种	英语
scopus关键词	Boundary layer flow; Hurricanes; Kinematics; Storms; Tropics; Wind; Boundary layer heights; Boundary layer structure; Mixed layer depths; Radial variations; Storm intensity; Tropical cyclone; Turbulent characteristics; Vertical gradients; Boundary layers; atmospheric dynamics; boundary layer; composite; storm; thermodynamics; tropical cyclone; wind velocity
来源期刊	Atmospheric Research
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/141656
作者单位	Shanghai Typhoon Institute, CMA, Shanghai, China; NOAA/AOML Hurricane Research Division, Miami, FL, United States; University of Miami, Cooperative Institute for Marine and Atmospheric Studies, Miami, FL, United States; Shanghai Central Meteorological Observatory, Shanghai, China; Department of Atmospheric and Oceanic Sciences, University of Wisconsin–Madison, Madison, WI, United States; Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin–Madison, Madison, WI, United States
推荐引用方式 GB/T 7714	Chen N.,Tang J.,Zhang J.A.,et al. On the distribution of helicity in the tropical cyclone boundary layer from dropsonde composites[J],2021,249.
APA	Chen N.,Tang J.,Zhang J.A.,Ma L.-M.,&Yu H..(2021).On the distribution of helicity in the tropical cyclone boundary layer from dropsonde composites.Atmospheric Research,249.
MLA	Chen N.,et al."On the distribution of helicity in the tropical cyclone boundary layer from dropsonde composites".Atmospheric Research 249(2021).