The Impact of Outer-Core Structure on Eye Formation and Intensification of Tropical Cyclones
Journal
Monthly Weather Review
Journal Volume
153
Journal Issue
2
Start Page
285
End Page
308
ISSN
0027-0644
1520-0493
Date Issued
2025-02
Author(s)
Chen, Yueh-Li
Abstract
The objectives of this study are to clarify the role of initial outer-core structure in intensity development and eye formation of tropical cyclones (TCs) and to examine the inner-core evolution in both the troposphere and lower stratosphere during intensification. A set of TCs with modified outer-core wind profiles of Typhoon Soudelor (2015) is set up. There are systematic variations of intensity, radius of maximum wind (RMW), and size, wherein larger initial vortices exhibit lower peak intensity, intensification rate, and RMW contraction rate and tend to maintain their larger size. While TCs in most of the experiments form their eyes through “clearing formation” processes, the largest experiment forms an eye through “banding formation” with more asymmetric eyewall convection. As compared to the largest TC, the smallest TC possesses low-level convergence and midlevel latent heating more concentrating inside the RMW with higher inertial stability and a stronger, deeper, and higher-altitude upper-level warm core. For the smallest TC, more subsidence warming is found in the lower stratosphere above the eyewall associated with more vigorous overshooting. The warmer air can be efficiently advected into the upper-level center since 1) the overshooting convection aggregates at a smaller radius and 2) the overshooting convection more frequently occurs at the upwind side of environmental flow owing to its higher angular velocity and faster axisymmetrization. It can be concluded that, for the smaller TCs, the more dominant role of the stratosphere in transporting much higher potential temperature downward appears to be the key leading to their higher intensification rate.
Subjects
Deep convection
Dynamics
Numerical analysis/modeling
Stratosphere
Tropical cyclones
Upper troposphere
Publisher
American Meteorological Society
Type
journal article