STRUCTURE OF A TROPICAL CYCLONE DEVELOPED IN A THREE-DIMENSIONAL NUMERICAL SIMULATION MODEL.

Abstract

A three-dimensional, 11-level, primitive equation model has been constructed for a simulation study of tropical cyclones. The model has four levels in the boundary layer and its 70 multiplied by 70 variable grid mesh encloses a 4000-km square domain with a 20-km resolution near the center. Details of the model, including the parameterization scheme for the subgrid-scale diffusion and convection processes, are described. Emphasis is placed on spiral bands which developed in the model in the outer region; the structure of those bands is extensively analyzed. The phase relationship among the pressure, horizontal motion, vertical motion, temperature and moisture fields is discussed. The spiral band behaves like an internal gravity wave. Once the band is formed in an area surrounding the center, it propagates outward apparently without appreciable further supply of energy.