Alerting of hectometric turbulence features at Hong Kong International Airport using a short-range LIDAR

The Doppler Lidar windshear alerting system at the Hong Kong International Airport (HKIA), the first of its kind in the world, has been in operation since 2006. This paper reports on an enhancement to the automatic windshear detection algorithm at HKIA, which aims at filtering out alerts associated with smoother headwind changes spread over longer distances along the aircraft glide path (called “gentle ramps”) which may nonetheless exceed the well-established alerting threshold. Real-time statistics are examined over a 46-month study period between March 2016 and December 2019, covering a total of 2,017,440 min and over 1500 quality-controlled pilot reports of windshear (PIREP). The “gentle ramp removal” (GRR) function is able to effectively cut down the alert duration over the 5 major runway corridors, inclusive of both landing and take-off, which together account for over 98% of the PIREP received at HKIA during the study period. In all 5 runway corridors this is achieved with a proportionately smaller decrease—even with no changes in 2 cases—in the hit rate, highlighting the efficiency of the GRR function. The difference in statistical behaviour across the runway corridors also echo literature findings about the differences in length scale of wind disturbances at different locations within HKIA. This study serves as a unique documentation of the state-of-the-art in operational Lidar windshear detection and can provide useful reference to airports and aviation meteorologists around the world.

Improving Lidar Windshear Detection Efficiency by Removal of “Gentle Ramps”

Effects of buildings on wind shear at the airport: Field measurement by coherent Doppler lidar

Tiny anticyclonic vortices have been observed at the arrival runway corridor to the east of the central runway of the Hong Kong International Airport many times. However, it is not sure about the cause of such vortices. In this paper, a meteorological model is coupled with a computational ﬂuid dynamics (CFD) model in high spatial resolution in an attempt to simulate such vortices. The performance of this coupled model is ﬁrst checked by comparing with the observed building wakes. This model is found to successfully capture the wakes and jets. It is then used to simulate the situation of anticyclonic vortex at the said region, with and without the presence of a key building called AsiaWorld-Expo. It is found that, with the presence of the building only, the anticyclonic vortex can be simulated. This adds more conﬁdence that such vortex is a result of the interaction between the background southwesterly ﬂow with the AsiaWorld-Expo.

Simulation of building-induced airflow disturbances in complex terrain using meteorological-CFD coupled model

Building-induced turbulence may affect aviation safety, e.g. when the aircraft is about to land at an airport.  Observations of such flow have been conducted at the Hong Kong International Airport using short-range LIDAR (SRL).  Statistical analysis of the radial velocity, namely, the longitudinal structure function, is described herein. It is found that the classical Kolmogorov theory for homogeneous turbulence applies to LIDAR observations of building-disrupted airflow.  Some distinctive features of the turbulent flow are also discussed, notably velocity streaks and tiny anticyclones at the hectometer scale.  The potential impact on a landing aircraft is examined and compared to flight data.  The results in this paper could be useful for studying building-induced turbulence at other airports around the world.

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Philipp Lux

Papers

Statistical analysis of building-induced turbulence at an airport