Application of LIDAR-derived eddy dissipation rate profiles in low-level wind shear and turbulence alerts at Hong Kong International Airport

In aviation meteorology, eddy dissipation rate (EDR) is an internationally-adopted metric for quantifying intensity of low-level turbulence (rapid, irregular headwind fluctuations experienced by an aircraft below 1600feet/500m). In this paper, calculations of EDR1/3 profiles along arrival corridors (07LA, 25RA) of the Hong Kong International Airport (HKIA) were performed over a 45month period (January to September, 2008-2012) based on radial velocity from a scanning Doppler LIDAR using the azimuthal velocity structure function approach. The quality of the LIDAR-estimated EDR was established by comparison with values calculated from in situ measurements over a 24month period, which showed that median values of EDR profiles from both sources fell within 0.05m(2/3)s(-1) of each other in over 90% (80%) of instances for 07LA (25RA). The performance in threshold-based alerting of low-level turbulence at HKIA was then validated against pilot reports. At alert duration of 10%, alerts based on the maximum value of an EDR profile could capture over 90% (80%) of reported events over 07LA (25RA), while comparable performance with the wind shear and turbulence warning system (WTWS) at HKIA was attainable using suitable alert thresholds. Positive skill, albeit inferior to WTWS, was also observed in the alerting of low-level wind shear (sustained headwind change of 15 knots or above below 1600feet/500m) with a hit rate of about 70% at alert duration of 10%. This study served to establish the value of EDR derived from ground-based remote-sensing instruments e.g. LIDAR in alerting of low-level turbulence for the aviation community.