Test of a Planetary Boundary-Layer Parameterization Based on a Generalized Similarity Theory in Tropical Cyclone Models

Simon Wei-jen Chang JAYCOR, Alexandria, VA 22304

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Abstract

A planetary boundary-layer (PBL) parameterization based on the generalized similarity theory (GST) was tested in tropical cyclone models. This parameterization, with only one layer, is desired in modeling tropical cyclones for computational speed. The momentum, sensible heat and moisture fluxes are mutually dependent in this parameterization through nondimensional gradient equations. The internal structure of the PBL is determined implicitly through universal functions.

In comparison with a complex, one-dimensional, multilayer PBL model, the GST parameterization yields accurate moisture fluxes, but slightly overestimates the momentum flux and underestimates the sensible heal flux. The GST parameterization produces very realistic dynamics, energetics and thermal structure in an axisymmetric tropical cyclone model. This GST parameterization, although unable to treat the diffusion across the PBL inversion, is judged superior to drag coefficient parameterization and is a good alternative to the more expensive, multilayer parameterization.

Abstract

A planetary boundary-layer (PBL) parameterization based on the generalized similarity theory (GST) was tested in tropical cyclone models. This parameterization, with only one layer, is desired in modeling tropical cyclones for computational speed. The momentum, sensible heat and moisture fluxes are mutually dependent in this parameterization through nondimensional gradient equations. The internal structure of the PBL is determined implicitly through universal functions.

In comparison with a complex, one-dimensional, multilayer PBL model, the GST parameterization yields accurate moisture fluxes, but slightly overestimates the momentum flux and underestimates the sensible heal flux. The GST parameterization produces very realistic dynamics, energetics and thermal structure in an axisymmetric tropical cyclone model. This GST parameterization, although unable to treat the diffusion across the PBL inversion, is judged superior to drag coefficient parameterization and is a good alternative to the more expensive, multilayer parameterization.

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