Concentric Eyewall Formation in Typhoon Sinlaku (2008) - Part III: Horizontal Momentum Budget Analyses
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Authors
Huang, Yi-Hsuan
Wu, Chun-Chieh
Montgomery, Michael T.
Subjects
Advisors
Date of Issue
2018-10
Date
10/01/2018
Publisher
American Meteorological Society (AMS)
Language
Abstract
This is a follow-up work to two prior studies examining secondary eyewall formation (SEF) in Typhoon Sinlaku (2008). This study shows that, in the SEF region, the majority of the elevated winds are supergradient. About two-thirds of the rapid increase in tangential wind tendencies immediately prior to SEF are attributed to agradient wind tendencies. This suggests the importance of nonlinear, unbalanced dynamical processes in SEF in addition to the classical axisymmetric balanced response to forcings of heating and momentum. In the SEF region, analyses show two distinct responsible processes for the increasing azimuthal tangential wind in two vertical intervals. Within the boundary inflow layer, the competing effect between the mean radial influx of absolute vorticity and deceleration caused by surface friction and subgrid diffusion yields a secondary maximum of positive tendency. Analyses further demonstrate the major impact of the mean radial influx of absolute vorticity on SEF. Above the boundary inflow layer, the vertical advection acts to vertically extend the tangential wind jet via the lofting of the enhanced tangential momentum farther upward. The roles of the nonlinear unbalanced dynamics in these two processes are discussed in this paper. From a Lagrangian per- spective, the persistently increasing agradient force outweighs the frictional loss, effectively decelerating boundary layer inflowing air across the SEF region. This explains the sharpening of the radial gradient of boundary layer inflow, which is shown to be responsible for the buildup of a zone with concentrated boundary layer convergence. The previously proposed unbalanced dynamical pathway to SEF is elaborated upon and supported by the current results and discussion.
Type
Article
Description
Part I may be found at https://doi.org/10.1175/MWR-D-11-00057.1
Part II may be found at http://hdl.handle.net/10945/36865
The article of record as published may be found at https://doi.org/10.1175/JAS-D-18-0037.1
Part II may be found at http://hdl.handle.net/10945/36865
The article of record as published may be found at https://doi.org/10.1175/JAS-D-18-0037.1
Series/Report No
Department
Meteorology
Organization
Identifiers
NPS Report Number
Sponsors
Ministry of Science and Technology, Taiwan
Division of Atmospheric and Geospace Sciences
Office of Naval Research Global
Division of Atmospheric and Geospace Sciences
Office of Naval Research Global
Funder
MTM acknowledges the support of NSF AGS-1313948, Office of Naval Research N0001417WX00336, and the U.S. Naval Postgraduate School.
Format
Citation
Huang, Yi-Hsuan, Chun-Chieh Wu, and Michael T. Montgomery. "Concentric Eyewall Formation in Typhoon Sinlaku (2008). Part III: Horizontal Momentum Budget Analyses." Journal of the Atmospheric Sciences 75.10 (2018): 3541-3563.