Prototype automatic LIDAR-based wind shear detection algorithms

The Hong Kong Observatory implemented a Doppler LIDAR at the Hong Kong International Airport (HKIA) in mid-2002 to enhance the detection and warning of wind shear under clear-air conditions.

Situated near the centre of the airport, the LIDAR has good coverage of the airport and its surrounding areas. Using data from PPI scans at elevation angles close to the glide paths, 2-dimensional shear features can be characterized. In addition, data from these PPI scans can be consolidated to construct headwind profiles along the respective glide paths.

In this paper, we present recent developments of two automatic LIDAR-based wind shear detection algorithms. The first algorithm attempts to identify 2-dimensional salient shear features on the PPI scans from radial shear segments. The second algorithm searches for wind shear signatures from the headwind profile constructed from the PPI scans for each glide path. Prototype graphical displays of the outputs of the two algorithms are given in Figures 1 and 2 respectively.

The performance of the two algorithms is being evaluated against wind shear reports provided by aircraft landing at or departing from HKIA. Results in terms of probability of detection, false alarm rate and other relevant performance metrics will be presented.

Figure 1. (a) LIDAR Doppler velocity display at 0 degree elevation, revealing a convergence line between a westerly sea breeze and background easterlies; (b) Prototype display of the LIDAR radial shear algorithm output derived from (a), identifying a 20-25 knots wind speed gain across the sea breeze front, in reasonable agreement with that reported by a landing aircraft at the same time.

Figure 2. Prototype display of another LIDAR windshear detection algorithm showing estimated head wind profiles along aircraft glide paths derived from multiple LIDAR PPI scans. A windshear of +20 knot was detected along the 07LA runway corridor and its location is highlighted in red on the head wind profile (upper-left) and on the LIDAR Doppler velocity composite display (centre).