Extended Abstract (56K)15A.5
Dynamical constraints on the maximum intensity of hurricanes
Roger K. Smith, University of Munich, Munich, Germany; and H. Zhu, W. Ulrich, and C. M. Nguyen
A ten layer axisymmetric version of the minimal hurricane model described by the first two authors (Zhu and Smith, 2003) is used to investigate the dynamical constraints on the maximum intensity of hurricanes. The model has a horizontal grid resolution of 10 km and latent heat release is represented explicitly using a simple algorithm. One series of calculations was carried out in which a vortex growing from the same initial disturbance is exposed to different levels of background rotation. A second series was carried out in which the size of the initial vortex is varied, keeping its intensity and the background rotation held fixed.
Preliminary results show that a given vortex growing in a region of enhanced background rotation such as in a monsoon trough reaches a significantly lower maximum intensity than one that grows in a more weakly rotating environment. In contrast, vortices that are initially broader reach a higher intensity than those that are narrower. The former are accompanied by a larger area of enhanced surface moisture fluxes and therefore have larger values of equivalent potential temperature in the boundary layer and the larger rotational constraint appears incapable of restraining the maximum intensity attained. The calculations point to the existence of dynamical constraints that are not explicitly included in existing theories for the maximum possible intensity of hurricanes.
Session 15A, Tropical cyclone intensity change IV: Numerical Modeling Studies
Thursday, 6 May 2004, 3:45 PM-5:00 PM, Le Jardin Room
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