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Absolute Angular Momentum Based Analytical Model for Tropical Cyclone Radial Wind Profiles

Title: An Absolute Angular Momentum Based Analytical Model for Tropical Cyclone Radial Wind Profiles.
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Name(s): Yan, Ruikai, author
Cai, Ming, 1957-, professor directing dissertation
Niu, Xufeng, 1954-, university representative
Chagnon, Jeffrey M., committee member
Speer, Kevin G. (Kevin George), committee member
Florida State University, degree granting institution
College of Arts and Sciences, degree granting college
Department of Earth, Ocean, and Atmospheric Science, degree granting department
Type of Resource: text
Genre: Text
Doctoral Thesis
Issuance: monographic
Date Issued: 2019
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource (206 pages)
Language(s): English
Abstract/Description: The ability to construct radial wind profiles of tropical cyclones (TC) from limited observations is crucial to the initialization of TC simulations and predictions. A minimum requirement for constructing a reasonable radial wind profile is a high skill in estimating one of the four TC characteristic parameters, namely maximum wind speed (Vmax), radius of maximum wind speed (rmax), 17 ms−1 wind speed (V17), and radius of 17 ms−1 wind (r17) from the other three. In this study, we put froth an absolute angular momentum (AAM) based analytical model for inferring the radial profile beyond the rmax from observations of these four parameters. An observed AAM loss L is defined as the ratio of the observed AAM at r17 to that at rmax. We parameterize the observed AAM loss L as an analytical function of these four parameters and environmental factors. The combination of analytical expressions of the AAM loss L and the AAM at r17 and rmax, gives us the analytical model. This observation-physics model allows us to construct radial profiles of TCs under four different configurations from observations of these four parameters. Specifically, we can use Vmax and rmax as inputs for solving (a) the tangential velocity profile of a TC from rmax to r17 or (b) the TC's radius for a given tangential velocity from Vmax to V17. Alternatively, we can use V17 and r17 as inputs for solving (c) the tangential velocity profile of a TC from r17 to rmax or (d) the TC's radius for a given tangential velocity from V17 to Vmax. This enables us to acquire radial wind profiles when one of the four parameters is not available in observations. The degree of consistency of (a) versus (c) and (b) versus (d) is an indicator of the robustness of the model. We evaluate the skill of our model using 4491 records of 197 named TCs derived from the Extended Best Track Dataset for the period of 1998-2016, and find that the mean errors in estimating Vmax, rmax, V17, and r17 are, respectively, 5.95 m/s, 25.37 km, 3.33 m/s, and 57.67 km. The proposed model has several advantages over widely recognized existing TC wind profile models. Most empirical models, for example, are designed to construct radial wind profiles in only one of the four configurations. While other physics-based models have mean errors in Vmax, rmax, and r17 that are larger by several factors. Furthermore, our model can yield physically realistic radial wind profiles and solutions of TC characteristic parameters (meaning that for radial wind profiles, wind velocity decreases monotonically from rmax to r17, and for solutions, Vmax > V17 > 0 and r17 > rmax > 0) for all 4491 TC records, regardless of which of the four configurations is chosen. For more than 10% of the TC records, however, other physics-based models have radial wind profiles that are discrete or increases from the inside to outside, and have solutions that either do not exist or are not physical under certain configurations.
Identifier: 2019_Summer_Yan_fsu_0071E_15321 (IID)
Submitted Note: A Dissertation submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
Degree Awarded: Summer Semester 2019.
Date of Defense: May 1, 2019.
Keywords: Analytical Model, Angular Momentum, Hurricane, Tropical Cyclone, Wind
Bibliography Note: Includes bibliographical references.
Advisory Committee: Ming Cai, Professor Directing Dissertation; Xufeng Niu, University Representative; Jeffery Chagnon, Committee Member; Kevin Speer, Committee Member; Guosheng Liu, Committee Member.
Subject(s): Atmospheric sciences
Meteorology
Persistent Link to This Record: http://purl.flvc.org/fsu/fd/2019_Summer_Yan_fsu_0071E_15321
Host Institution: FSU

Choose the citation style.
Yan, R. (2019). An Absolute Angular Momentum Based Analytical Model for Tropical Cyclone Radial Wind Profiles. Retrieved from http://purl.flvc.org/fsu/fd/2019_Summer_Yan_fsu_0071E_15321