New Observations of Airflow at Hong Kong International Airport by Range Height Indicator (RHI) Scans of LIDARs and Their Numerical Simulation

Range height indicator (RHI) scans are performed routinely by the long-range Doppler Light Detection and Ranging (LIDAR) systems at the Hong Kong International Airport (HKIA). This paper presents some novel observations of the airflow in the airport region by RHI scans that have not been reported in the literature in the past—namely, areas of reverse flow and vortex shedding in east to southeasterly winds; severe windshear in the easterly; a converging southerly flow; a descending northeasterly jet; and the undercutting of the southwesterly flow by sea breeze. Many of these flow features are associated with low-level windshear, supported by pilot windshear reports, and thus their observations have practical applications. The technical feasibility of forecasting these airflow features is also studied in this paper, and it is found that large eddy simulations based on a mesoscale meteorology model manage to capture these wind features most of the time, but the simulated headwind change is generally slightly smaller than observed. The results in this paper have application value for windshear alerting and forecasting for an airport situated in an area of complex terrain, and they should be of interest for further studies of mountain meteorology.