Plenary Lecture

Plenary Lecture

Models of Aerodynamics and Physics of Hurricanes

Professor A. I. Leonov
The University of Akron, Akron
OH 44325-0301, U.S.A.

Abstract: Theoretical models have been developed to describe the aerodynamics and physics in quasi-steady hurricanes moving over open seas. The vertical structure of hurricane was modeled as consisting of lower, hurricane boundary layer (HBL) and upper, quasi-adiabatic layer, connected by a thin condensation layer in the eye wall region. Except the friction at the air/sea interface, the modeling avoided the common turbulent approximations, while explicitly or implicitly used basic stability constraints.
Based on observations, it was assumed that the hurricanes propagate along the warm air bands located over the warm oceanic currents, and under action of "sailing" wind. It was also assumed that the mass, humidity, momentum, and angular momentum of air are transferred from the lower to upper hurricane layers through the hurricane eye wall.
The air wind in HBL is highly affected by several physical processes, which have also been analyzed: (i) a specific oceanic wave air interaction, (ii) evaporation at the sea surface, (iii) horizontal thermal flux from the warm air band to the hurricane core, and (iv) sudden condensation at the upper boundary of HBL, which is treated similar to slow combustion. Aerodynamic analyses of HBL resulted in space distributions of dynamic and thermodynamic variables. Additionally, a set of integral balance relations established for HBL, allowed expressing the key hurricane parameters via the horizontal temperature drop and sailing wind speed, which are considered to be given.
The HBL model was coupled with the model of upper AL of hurricane. Analysis of AL established a stability constraint for existence of steady hurricane, and resulted in analytical formulas for space distributions of dynamic variables. The values of key hurricane variables calculated using the coupled model, seem to be realistic.
Several observed effects have been explained and quantitatively described using this modeling. They include: (i) change in direction of hurricane angular velocity from cyclonic in lower part of hurricane to anti-cyclonic in the upper one, (ii) change in radial direction of radial wind component from centripetal in the lower part of hurricane to the centrifugal in its upper part, (iii) change in the radial distribution of angular momentum from radially increased in HBL to a constant value in AL, and (iv) sudden increase of temperature at the upper part of HBL.
The following three-step model of hurricane genesis and maturing in sub-tropical zones has been proposed and analyzed: (i) a sudden formation of plume; (ii) rotating the plume initiated by the horizontal component of trading wind, and (iii) propagation of external boundary of rotated plume due to the Kelvin-Helmholtz instability and under action of Coriolis force. A simple model showed that outward propagation of just formed rotational plume is possible only if the initial rotation of plume is cyclonic. The model calculations demonstrate very realistic features as compared with observations.
Based on these models, a simple idea of hurricane destabilizing by flights of supersonic jets has been proposed.

Brief Biography of the Speaker:
Arkady I. Leonov is a full professor at the Department of Polymer Engineering, and adjunct professor of applied mathematics at the University of Akron, Ohio, USA. He worked in broad scientific areas: classic and polymer related continuum mechanics of solids and liquids, geophysical fluid mechanics, polymer rheology and polymer fluid mechanics, polymer physics and physico-chemistry, polymer processing, and mathematical sociology. He authored and co-authored over 200 scientific papers published in reviewed journals, made numerous presentations at national and international conferences, published alone or with colleagues' four scientific monographs and four book chapters. He is a member of Society of Rheology, American Academy of Mechanics, and Honorable Member of British Society of Rheology. The presentation topics have been preliminary published in Electronic Arxiv Journal, Physics of Atmosphere and Ocean, 2008.

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