Some Relations Between Wind and Thermal Structure of Steady State Hurricanes

Abstract

Several simple integrations are performed to determine to what extent a steady, symmetrical hurricane model can be used to approximate observed storm structure. A two-layer model with inflow and outflow is considered. In the outflow, the absolute angular momentum about the vertical axis at the hurricane center is conserved. In the inflow, conservation of potential vorticity is assumed. For specified outer boundary conditions this assumption determines the distribution of momentum transport from air to ocean and there-with the radial profile of the tangential wind component. The local heat source at the ocean surface is assumed to supply the energy for the generation of hurricane winds. Given this heat source and the vertical wind shear between inflow and outflow layers from the dynamic model, a relation must exist between heat source and momentum sink at the air-water interface, if a particular wind field is to exist in steady state. This relation is computed. Various empirical tests are performed to assess the degree of reality of the model. Observations from hurricanes between 1945 and 1958 are used. Most observational material is taken from research missions conducted by aircraft of the National Hurricane Research Project. The crude model gives a rather good approximation to several hurricanes, especially the more intense ones. But it cannot explain an measurements taken by NHRP; of course, steady state did not exist in all situations investigated by aircraft. It may be concluded that computations with steady, symmetrical models are relevant at least to partial understanding of hurricanes.