Extended Abstract (180K)10D.1
Simulation of tropical cyclones using the GFDL TC model with bulk parameterization and spectral microphysics
Robert E. Tuleya, NOAA/GFDL, Princeton, NJ; and M. Bender and A. P. Khain
The evolution of tropical cyclones (TC), especially their intensity and structure depend on the magnitude and spatial distribution of convective heating within a TC. The associated precipitation rate and amount depend on the microphysical structure of clouds, of size of drops and type and size of cloud ice. Convective parameterization schemes traditionally used for TC simulation were designed for models with comparatively crude resolution unable to resolve individual cumulus clouds. These schemes are based on some semi-empirical or semi-intuitive assumptions, concerning convection response to large-scale forcing. These schemes lead, as a rule, to different TC intensities, structure and, sometimes, to substantially different tracks. In addition, these schemes which do not include microphysical processes often result in significant variations in precipitation forecasts. At the same time, the increased resolution of many advanced TC models allows convection to be explicity resolved in the vicinity of TC center, where convection is concentrated. This is especially true in the zone of the eye wall, where clouds are large, having diameters up to several kilometers.
Two convective schemes have been recently implemented into the GFDL tropical cyclone model. The first one is a bulk-parameterization scheme based mainly on study by Lin et al (1983). This scheme has been successfully used in the Goddard Cloud ensemble model (Tao et al, 2001), as well as in other high resolution mesoscale models for simulation of storms. It describes the formation and transport of cloud hydrometeors of five types: cloud water (small cloud droplets), raindrops, ice crystals, snowflakes (aggregates), and graupel. The second scheme developed at the Hebrew University of Jerusalem (Khain et al, 2000; 2001) is based on solving equation system for size distribution functions for liquid water, plate-, columnar,- and branch-type ice crystals, aggregates, graupel, hail/frozen drops. The scheme is designed in such a way to describe effect of atmospheric aerosol on formation of droplet and ice size spectra and precipitation.
The evolution and structure of tropical cyclones obtained using the current parameterization scheme (Kurihara,1973), bulk-parameterization and spectral microphysics will be compared in both axisymmetric and three dimensional domain configurations. Special attention will be paid to differences in intensity, structure, precipitation rate and profiles of convective heating. In additon, fields of radar reflectivity will be calculated and compared with precipitation rates and observed data at different stages of TC development.
Session 10D, Tropical Cyclone Simulation: Parameterizations and Numerics (Parallel with Sessions 10A, 10B, and 10C)
Wednesday, 1 May 2002, 2:00 PM-3:30 PM
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