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| Titel |
Lagrangian coherent structures in tropical cyclone intensification |
| VerfasserIn |
B. Rutherford, G. Dangelmayr, M. T. Montgomery |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 12 ; Nr. 12, no. 12 (2012-06-22), S.5483-5507 |
| Datensatznummer |
250011280
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| Publikation (Nr.) |
 copernicus.org/acp-12-5483-2012.pdf |
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| Zusammenfassung |
Recent work has suggested that tropical cyclones intensify via a pathway of
rotating deep moist convection in the presence of enhanced fluxes of moisture
from the ocean. The rotating deep convective structures possessing enhanced
cyclonic vorticity within their cores have been dubbed Vortical Hot Towers
(VHTs). In general, the interaction between VHTs and the system-scale vortex,
as well as the corresponding evolution of equivalent potential temperature
(θe) that modulates the VHT activity, is a complex problem in
moist helical turbulence.
To better understand the structural aspects of the three-dimensional
intensification process, a Lagrangian perspective is explored that focuses on
the coherent structures seen in the flow field associated with VHTs and their
vortical remnants, as well as the evolution and localized stirring of
θe. Recently developed finite-time Lagrangian methods are
limited in the three-dimensional turbulence and shear associated with the
VHTs. In this paper, new Lagrangian techniques developed for
three-dimensional velocity fields are summarized and we apply these
techniques to study VHT and θe phenomenology in a
high-resolution numerical tropical cyclone simulation. The usefulness of
these methods is demonstrated by an analysis of particle trajectories.
We find that VHTs create a locally turbulent mixing environment. However,
associated with the VHTs are hyperbolic structures that span between adjacent
VHTs or adjacent vortical remnants and represent coherent finite-time
transport barriers in the flow field. Although the azimuthally-averaged
inflow is responsible for the inward advection of boundary layer
θe, attracting Lagrangian coherent structures are coincident
with pools of high boundary layer θe. Extensions of boundary
layer coherent structures grow above the boundary layer during episodes of
convection and remain with the convective vortices. These hyperbolic
structures form initially as boundaries between VHTs. As vorticity aggregates
into a ring-like eyewall feature, the Lagrangian boundaries merge into a ring
outside of the region of maximal vorticity. |
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