VALIDATING THE TURBULENCE PARAMETERIZATION SCHEMES OF A NUMERICAL MODEL USING EDDY DISSIPATION RATE MEASUREMENTS IN A TERRAIN-DISRUPTED AIRFLOW

摘要

A number of turbulence parameterization schemes are available in the latest version (6.0) of the Regional Atmospheric Modelling System (RAMS). Chan (2009) studied the performance of these schemes by simulating the eddy dissipation rate (EDR) distribution in the vicinity of the Hong Kong International Airport (HKIA) and comparing with the EDR measurements of remote-sensing instruments at the airport. For the e-1 (turbulent kinetic energy — mixing length) scheme considered in that study, the mixing length is assumed to be a constant. This assumption is removed in the present paper and simulations of EDR fields are repeated for terrain-disrupted airflow in the vicinity of HKIA. It is found that, with a variable mixing length, the performance of the e-1 scheme is greatly improved. With suitable choice of the empirical constants in the turbulence closure, the accuracy of the EDR profile (in comparison with LIDAR and wind profiler measurements) is found to be comparable with that predicted by the Deardorff scheme. A study on the sensitivity of the simulation results to these empirical constants has also been performed.