Kinetic energy efficiencies of idealized developing tropical cyclones

Daniel P. Stern, David S. Nolan

Research output: Contribution to conferencePaper

1 Scopus citations

Abstract

The goal of this study is to investigate the influence that the internal structure of a hurricane-like vortex has on its own intensification. Specifically, we have quantified the amount of kinetic energy which is retained by a vortex following the introduction of a given heat perturbation, and determined how this efficiency systematically varied with vortex structure. Significant conclusions are the following: The final balanced response of a vortex following a symmetric heating perturbation centered at the RMW is a strengthening and broadening of the warm core. Since the maximum temperature change occurs between the center and the RMW, this is where the maximum pressure falls occur, tightening the gradient, and increasing the maximum windspeed. Latent heat release would be theoretically most effective if it occurred at the center of the vortex and at and somewhat above the height of the warm core center. This is the region where inertial (static) stability is greatest (smallest). Stronger vortices are much more efficient than weaker ones, in agreement with previous studies. For every 10 m/s increase in windspeed, efficiency increases by 0.7-1%. While that may seem small, it means that a 40 m/s vortex is about 7 or 8 times more efficient than a 10 m/s vortex. Vortices at higher latitudes are significantly more efficient due to their increased inertial stability. The effect of RMW appears to depend on the radial profile of vorticity outside the RMW, with a positive trend with increasing RMW for Gaussian vortices, little to no effect for a pure Rankine vortex, and a strongly negative trend for modified Rankine vortices with broad wind fields. The efficiencies of modified Rankine vortices are very sensitive to the decay rate of the tangential wind beyond the RMW. Vortices with very slowly decaying winds (a = 0.1) can be 3 times more efficient than a pure Rankine vortex. This implies that the intensification rates of real tropical cyclones may be highly dependent on the structure of the wind field outside of the core.

Original languageEnglish (US)
StatePublished - Dec 1 2006
Event27th Conference on Hurricanes and Tropical Meteorology - Monterey, CA, United States
Duration: Apr 24 2006Apr 26 2006

Other

Other27th Conference on Hurricanes and Tropical Meteorology
CountryUnited States
CityMonterey, CA
Period4/24/064/26/06

ASJC Scopus subject areas

  • Environmental Engineering
  • Global and Planetary Change

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    Stern, D. P., & Nolan, D. S. (2006). Kinetic energy efficiencies of idealized developing tropical cyclones. Paper presented at 27th Conference on Hurricanes and Tropical Meteorology, Monterey, CA, United States.