Axisymmetric Balance Dynamics of Tropical Cyclone Intensification and its Breakdown Revisited
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Authors
Smith, Roger K.
Montgomery, Michael T.
Bui, Hai
Subjects
Advisors
Date of Issue
2018-09
Date
09/01/2018
Publisher
American Meteorological Society
Language
en_US
Abstract
This paper revisits the evolution of an idealized tropical cyclone–like vortex forced by a prescribed distribution of diabatic heating in the context of both inviscid and frictional axisymmetric balance dynamics. Prognostic solutions are presented for a range of heating distributions, which, in most cases, are allowed to contract as the vortex contracts and intensifies. Interest is focused on the kinematic structure and evolution of the secondary circulation in physical space and on the development of regions of sym- metric and static instability. The solutions are prolonged beyond the onset of unstable regions by regularizing the Sawyer–Eliassen equation in these regions, but for reasons discussed, the model ultimately breaks down. The intensification rate of the vortex is essentially constant up to the time when regions of instability ensue. This result is in contrast to previous suggestions that the rate should increase as the vortex intensifies because the heating becomes progressively more "efficient" when the local inertial stability increases. The solutions provide a context for reexamining the classical axisymmetric paradigm for tropical cyclone intensification in the light of another widely invoked intensification paradigm by Emanuel, which postulates that the air in the eyewall flows upward and outward along sloping absolute angular momentum (M) surfaces after it exits the frictional boundary layer. The conundrum is that the classical mechanism for spinup requires the air above the boundary layer to move inward while materially conserving M. Insight provided by the balance solutions helps to refine ideas for resolving this conundrum.
Type
Article
Description
The article of record as published may be found at https://doi.org/10.1175/JAS-D-17-0179.1
Series/Report No
Department
Meteorology
Organization
Identifiers
NPS Report Number
Sponsors
Office of Naval Research
German Research Council
National science Foundation
NOAA HFIP
NASA
U.S. Naval Postgraduate School
German Research Council
National science Foundation
NOAA HFIP
NASA
U.S. Naval Postgraduate School
Funder
MTM acknowledges the sup- port of NSF Grant AGS-1313948, NOAA HFIP Grant N0017315WR00048, NASA Grant NNG11PK021, ONR Grant N0001417WX00336, and the U.S. Naval Postgraduate School.
Format
Citation
Smith, Roger K., Michael T. Montgomery, and Hai Bui. "Axisymmetric balance dynamics of tropical cyclone intensification and its breakdown revisited." Journal of the Atmospheric Sciences 75.9 (2018): 3169-3189.