How does the eye warm? Part II

Sensitivity to vertical wind shear and a trajectory analysis

Daniel P. Stern, Fuqing Zhang

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

In Part II of this study, idealized simulations of tropical cyclones are used to investigate the influence of vertical wind shear on the structure of warming and descent in the eye; results are compared with the no-shear simulation that was analyzed in Part I. During intensification of a tropical cyclone in a quiescent environment, time-averaged eye descent is maximized at 12-13-km height. Warming is not generally maximized at these levels, however, because the static stability is at a minimum. Consequently, the perturbation temperature is maximized at midlevels. Each of the above results remains valid for sheared tropical cyclones, and therefore shear does not systematically alter the height of the warm core. An analysis of over 90 000 parcel trajectories yields further insight into the mechanisms of eye warming and addresses several outstanding questions regarding the character of eye descent. The rate at which parcels are stirred from the eye into the eyewall is a strong function of intensity. While stirring is large at the beginning of rapid intensification (RI), once a sufficient intensity is achieved, most parcels originating near the storm center can remain inside the eye for at least several days. Many parcels in the upper troposphere are able to descend within the eye by 5-10 km. The above results are relatively insensitive to the presence of up to 10 m s21 of shear. In contrast, stirring in the eye-eyewall interface region is substantially enhanced by shear.

Original languageEnglish (US)
Pages (from-to)1849-1873
Number of pages25
JournalJournal of the Atmospheric Sciences
Volume70
Issue number7
DOIs
StatePublished - Aug 14 2013

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wind shear
trajectory
tropical cyclone
warming
analysis
simulation
troposphere
perturbation

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

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abstract = "In Part II of this study, idealized simulations of tropical cyclones are used to investigate the influence of vertical wind shear on the structure of warming and descent in the eye; results are compared with the no-shear simulation that was analyzed in Part I. During intensification of a tropical cyclone in a quiescent environment, time-averaged eye descent is maximized at 12-13-km height. Warming is not generally maximized at these levels, however, because the static stability is at a minimum. Consequently, the perturbation temperature is maximized at midlevels. Each of the above results remains valid for sheared tropical cyclones, and therefore shear does not systematically alter the height of the warm core. An analysis of over 90 000 parcel trajectories yields further insight into the mechanisms of eye warming and addresses several outstanding questions regarding the character of eye descent. The rate at which parcels are stirred from the eye into the eyewall is a strong function of intensity. While stirring is large at the beginning of rapid intensification (RI), once a sufficient intensity is achieved, most parcels originating near the storm center can remain inside the eye for at least several days. Many parcels in the upper troposphere are able to descend within the eye by 5-10 km. The above results are relatively insensitive to the presence of up to 10 m s21 of shear. In contrast, stirring in the eye-eyewall interface region is substantially enhanced by shear.",
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How does the eye warm? Part II : Sensitivity to vertical wind shear and a trajectory analysis. / Stern, Daniel P.; Zhang, Fuqing.

In: Journal of the Atmospheric Sciences, Vol. 70, No. 7, 14.08.2013, p. 1849-1873.

Research output: Contribution to journalArticle

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