This study is concerned with the dynamic and thermodynamic structure of hurricane type circulations. The storm is taken to be symmetric about a vertical axis through its centre, and cylindrical isobaric polar coordinates are used throughout. The possibility of obtaining a time dependent solution by the use of time similarity variables is explored. An analytic solution is found for the dynamical equations of a mature hurricane system in a quasi-stationary state. The solution is based on (i) eddy viscosity coefficients Kl and K2, describing vertical and horizontal transfers of momentum respectively, expressed initially as general functions of p , and (ii) the premise that the radial variation in the magnitudes of the tangential and radial components of velocity are of a similar form. Explicit expressions for Kl and K2 are finally obtained by choosing power law forms, in the p variable, which lead to good agreement between model results and typical observed distributions of the three mean velocity components over the dynamically active region of the storm. By using this (inverse) method of calculating Kl and K2 and an analytic model, the whole eddy system, ranging from those created by the very strong velocity shear close to the sea surface to those connected with violent cloud convection, is described by continuous mathematical functions. The need for a separate boundary layer is avoided. The associated temperature and condensation heating distributions are then calculated from the hydrostatic relation and the thermodynamic equation. To complete the model an integral flux condition for the total evaporation from the sea surface is used to obtain the sea surface temperature for a given input of water vapour at the outer wall of the model. Numerical experiments are carried out which, together with an examination of the basic functional forms involved in the solution, enable the model dynamics to be related to changes in the numerical values of various physical parameters. By considering the model sea temperature for storms having a given kinetic energy, the preferred radial distribution of tangential velocity for such a storm is obtained. It is found that the height of the maximum tangential velocity, the 'steering height', is required to be between 850 and 900mb from thermal considerations. The range of functional variation in the formulation of the eddy terms that can support realistic storm cells is examined, and an investigation is made of the consequences of variation in the Coriolis parameter.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:454960 |
| Date | January 1977 |
| Creators | Evans, H. P. |
| Publisher | University of Exeter |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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