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in a nonlinear barotropic model. The results show that when an asymmetric
perturbation is placed at twice of RMW, an asymmetric disturbance
develops in the inner core region, resulting in a weakening of the symmetric
tangential wind. However, the symmetric flow gains energy from the
asymmetric perturbations in the outer region, which induces the second
peak of the symmetric tangential wind. This process is robust for both the
wavenumber 2 and 3 perturbations, pointing out a new wave-mean flow
interaction scenario for the double eyewall formation.
The numerical simulations illustrate that two distinctive symmetry-
asymmetry interaction regimes in the inner and outer regions, respectively.
While the symmetric tangential wind exhibits an oscillatory evolution in the
inner region, it grows steadily in the outer region. This distinctive evolution
feature is closely related to the asymmetric vorticity pattern, its up- or
down-shear tilt, and so-induced symmetry-to-asymmetry or asymmetry-to-
symmetry energy transfer.
Sensitivity numerical experiments indicate that there exists an optimal
radius location (approximately near twice of the radius of the maximum
wind) where the initial asymmetric disturbance may generate the most
significant double-peak structure in the tangential wind profile. The optimal
radius exists in both the wavenumber 2 and 3 experiments.
In the current study, a simple nonlinear barotropic model is used.
Further studies with more sophisticated models are needed to validate the
wave-mean flow interaction processes.
Acknowledgments
This work was supported by ONR grants N000140710145 and
N000140210532, NRL subcontract N00173-06-1-G031, and National
Natural Science Foundation of China under Grants 40205009 and 40333025.
The International Pacific Research Center is partially sponsored by the
Japan Agency for Marine-Earth Science and Technology (JAMSTEC). This
is SOEST publication number 1234 and IPRC publication number 123.
References
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