Midlevel Ventilation's Constraint on Tropical Cyclone Intensity
Author(s)
Tang, Brian Hong-An; Emanuel, Kerry Andrew
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Midlevel ventilation, or the flux of low-entropy air into the inner core of a tropical cyclone (TC), is a hypothesized mechanism by which environmental vertical wind shear can constrain a tropical cyclone’s intensity. An idealized framework based on steadiness, axisymmetry, and slantwise neutrality is developed to assess how ventilation affects tropical cyclone intensity via two possible pathways: the first through downdrafts outside the eyewall and the second through eddy fluxes directly into the eyewall. For both pathways, ventilation has a detrimental effect on tropical cyclone intensity by decreasing the maximum steady-state intensity significantly below the potential intensity, imposing a minimum intensity below which a TC will unconditionally decay, and providing an upper-ventilation bound beyond which no steady tropical cyclone can exist. Ventilation also decreases the thermodynamic efficiency as the eyewall becomes less buoyant relative to the environment, which compounds the effects of ventilation alone. Finally, the formulation presented in this study is shown to be invariant across a range of thermodynamic environments after a suitable normalization and shows little sensitivity to external parameters.
Date issued
2010-06Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary SciencesJournal
Journal of Atmospheric Sciences
Publisher
American Meteorological Society
Citation
Tang, Brian, Kerry Emanuel, 2010: Midlevel Ventilation’s Constraint on Tropical Cyclone Intensity. J. Atmos. Sci., 67, 1817–1830.
doi: 10.1175/2010JAS3318.1 © 2010 American Meteorological Society
Version: Final published version
ISSN
1520-0469
0022-4928