Monday, 30 July 2001
Evaluation of a Turbulent Mixing Length Parameterization Applied to the Case of an Approaching Upper-Tropospheric Trough
A method for estimating mixing length in the prediction of
turbulent kinetic energy by the Navy's Coupled Ocean/Atmosphere
Mesoscale Prediction System (COAMPS) has been documented (Walters
and Miller 1999, Walters and Miller 2001). The sensitivity of
the method to initial conditions and to model vertical and
horizontal resolution will be presented for conditions of low
and moderate upper-tropospheric turbulence which occurred on
18 April 2000 over Albuquerque, New Mexico, with the approach
of a cut-off low pressure system. The variability of the COAMPS
turbulent kinetic energy solution for (1) cold-start initializations
using NOGAPS or ETA as first guess fields, (2) a varying number of
allowable first guess model vertical levels, and (3) different COAMPS
horizontal and vertical resolutions will be compared to observations
of integrated optical turbulence. Turbulence in COAMPS is generated
using a modified form of the Mellor and Yamada (1982) 2.5 closure
scheme for parameterizing mixing length with the Bougeault and
Lacarrere (1989) scheme for computing optical turbulence.
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