A Preliminary Experiment of the Tropical Cyclone without Parameterizing the Effects of Cumulus Convection

Abstract

As an approach to study the development and structure of the tropical cyclone, a numerical experiment is performed with the use of a fine-resolution model in which convective clouds as well as larger-scale motions can be treated explicitly. For simplicity and because of computational limitations, a two-dimensional model is adopted with an assumption of axial symmetry, and a tropical cyclone of very small horizontal scale is treated. An initial condition is taken such that the temperature profile is similar to that of the mean tropical atmosphere in summer but the relative humidity is much higher in the lower atmosphere. The motions are assumed to be at rest and buoyancy perturbations are introduced for the initiation of clouds (and large-scale motions). Results of the numerical experiment indicate that a disturbance develops through its interaction with convective clouds in the conditionally unstable stratification. Except for an extremely small horizontal scale realized, the structures of the disturbance are similar to those of the tropical cyclone; the eye and eyewall structure, realistic tangential and radial velocity fields having inflow concentrated near the surface, and so on. The behaviors and the structures of the disturbance as well as rainfall characteristics are discussed in comparison with those obtained from parameterized models of the tropical cyclone and observations.