HR: 09:45h
AN: A41F-06    [Abstracts]
TI: Simulating Tropical Precipitation Using the Weak Temperature Gradient Approximation
AU: * Perez, C L
EM: cristina@iri.columbia.edu
AF: Columbia University IRI, 202 Monell Bldg. P.O. Box 1000, Palisades, NY 10964-8000 United States
AU: Sobel, A H
EM: ahs129@columbia.edu
AF: Depatment of Applied Physics and Applied Mathematics, S.W. Mudd, Room 217 Columbia University 500 West 120th Street, New York, NY 10027 United States
AB: Tropical precipitation due to deep convection is typically forced in limited area models by specifying the large-scale vertical velocity or vertical advection terms. Since the dominant thermodynamic balance in the tropics is between adiabatic cooling and diabatic heating (or vice versa), and the latter is due mostly to precipitating convection, the standard approach determines the model precipitation rate almost independently of model physics. The model thus cannot be used to address the question: what causes deep convection to occur or not occur? We apply an alternate approach, based on the Weak Temperature Gradient (WTG) approximation, to a 2-D cloud resolving model, the Goddard Cumulus Ensemble Model (GCEM), to address this question. We first varied the sea surface temperature (SST) and examined the resulting statistically steady states simulated by the model, focusing on the total precipitation and rain rate. The precipitation and rain rate increase strongly and nonlinearly with SST in our simulations. Subsequent experiments with the GCEM in WTG mode were designed to study the effects of varying surface wind speed, vertical wind shear, horizontal moisture advection on precipitation. We will also present results of sensitivity tests of the model response to changes in the microphysics parameters.
DE: 3300 METEOROLOGY AND ATMOSPHERIC DYNAMICS
DE: 3314 Convective processes
DE: 3354 Precipitation (1854)
DE: 3374 Tropical meteorology
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly