A further study of a special event of low-level windshear at the Hong Kong International Airport

Abstract

This is a follow-up study of a special windshear case at the Hong Kong International Airport.  In the previous study, the airflow disturbances observed by the Doppler LIDAR for cross-mountain airflow could reasonably be reproduced in the simulation, but there are two aspects that are not simulated so satisfactorily, namely, the jumps in temperatures and dew points at the weather buoys over the sea to the west of the airport and the reverse airflow at that area.  The present study considers a number of model setups in order to reproduce these two features, namely, the use of different numerical weather prediction models, the choice of vertical co-ordinate system and the choice of turbulence parameterization scheme. It is found that the use of Weather Forecasting and Research (WRF) model with MYNN turbulence parameterization scheme seems to give the best results. The choice of vertical co-ordinate system appears to be secondary. The mechanism for the rapid fall and rise in temperatures and dew points is investigated further based on the simulation result.  They are found to be related to a change of the flow regime in the airport area, namely, from prevailing easterly flow from the airport, to a more southerly flow crossing the mountains. The present study may serve as a reference for simulating wind flow in areas of complex terrain with a high spatial resolution using mesoscale numerical weather prediction models.