Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165

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Influence of Low-Level, High-Entropy Air in the Eye on Tropical Cyclone Intensity: A Trajectory Analysis
Xingyang ZHOULiguang WUQingyuan LIUYan ZHENG
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JOURNAL OPEN ACCESS Advance online publication

Article ID: 2020-063

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Abstract

 Previous studies suggested that the entrainment of the low-level, high-entropy eye air can provide additional energy for tropical cyclone (TC) intensification, but the previous trajectory analysis only indicated that considerable air parcels below the eye inversion can be entrained into the eyewall. In this study, the one-minute output data from a semi-idealized experiment are used to quantitatively evaluate the relative importance of the entrainment of the high-entropy eye air by enhancing the eyewall convection.

 It is confirmed that considerable amount of high-entropy eye air below the eye inversion can be entrained into the eyewall. The entrainment occurs favorably on the quandrants of enhanced eyewall convection and is enhanced in the presence of small-scale disturbances in the inner edge of the eyewall. However, the eyewall air parcels below 3 km experience a fast cycling. There are 84.4 % and 7.7 % eyewall air from the low-level boundary inflow and the middle-level dry environment, respectively. The low-level, high-entropy eye air only accounts for 1.7 % of the eyewall air, while 6.2 % eyewall air remains in the eyewall below 3 km during the 90-minute period. The eye air from the low-level, high-entropy reservoir accounts for 5.8 % of the equivalent potential temperature change below 3 km and 4.5 % of the total mass transport at 3 km in the TC eyewall. This study suggests that the low-level, high-entropy air from the eye has little direct influence on TC intensity through enhancing the eyewall convection by providing relatively small mass and thermodynamic contributions.

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© The Author(s) 2020. This is an open access article published by the Meteorological Society of Japan under a Creative Commons Attribution 4.0 International (CC BY 4.0) license.
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