Trial Use of Short-range Light Detection and Ranging System for Windshear Detection

A pilot study of Short-Range Light detection and ranging system (SRL) on windshear detection for the arrival runway corridor to the east of the north runway (25RA) of the Hong Kong International Airport (HKIA) was conducted in 2009-2011. The SRL was installed on the rooftop of the AsiaWorld-Expo to monitor transient and fine-scale airflow disturbances over 25RA that might be associated with low-level wind effects of the buildings/man-made structures. The SRL possesses a higher spatial resolution down to 75 metres and a temporal resolution down to 20 seconds (as compared with a resolution of about 100 metres and a revisit time of about 2 minutes for the operational long-range LIDAR system) over 25RA.

In the trials so far, SRL demonstrated capability of capturing the airflow disturbances over 25RA that might lead to low-level windshear. Using pilot reports as 'sky truth', SRL, when used in combination with Windshear and Turbulence Warning System, achieves a hit rate of about 92% (comparable with that of the existing overall windshear alerting service) but with a much shorter alert duration of 10% of the period (c.f. 17% of the overall service). The Observatory is considering to install a permanent unit of SRL along the seaside near AsiaWorld-Expo in 2019 in order to further enhance the windshear and turbulence alerting service, in particular to address the windshear due to low-level wind effects of buildings.

Figure 1  SRL wind velocity images on 29 June 2011. The arrow indicates the movement of the higher wind speed area as marked by the red ellipse within the two-minute period.