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A wind-shear now-casting system for Hong Kong International Airport is described. The system has been configured and run retrospectively for the period from January to April 2018 at 20-min intervals using two sets of meteorological inputs to quantify uncertainty. Outputs from the system include calculations of headwind for the northerly and southerly runways at the airport. Six metrics have been defined that attempt to identify areas of strong wind shear; these involve quantification of headwind and headwind gradient in both the horizontal and vertical directions. Receiver operating characteristic (ROC) curves have been generated for all metrics, runways, and meteorological conditions using pilot wind-shear reports to define wind-shear events. These curves allow for derivation of metric thresholds that could be used within an operational system to provide wind-shear alerts. The skill of the system for the 4-month period was quantified in terms of the probability of detection (POD, ideal value 1.0) of wind-shear events; system performance was better for the southerly runway, with the majority of POD values in the range 0.6 to 0.8. [ABSTRACT FROM AUTHOR]

With the aim of developing a forecasting system for the prediction of adverse meteorological conditions in the vicinity of complex terrain for aircraft landing at Hong Kong International Airport, the linearized, quasi‐empirical FLOWSTAR model has been configured to represent a series of eight landing events (2015–2017); half of these events reported significant wind shear and, for two, the landing attempt was aborted. Meteorological data used as input to the model have been derived from Hong Kong Observatory radiosonde measurements; these are the most reliable available despite being recorded at a location distant from the airport and at one or more hours before or after landing events. In general, the model predicts stronger wind shear for cases where adverse conditions have been reported. Analysis of the magnitude of wind shear generated as a result of wind veering and backing helps to quantify the importance of nonlinear flow features such as trapped lee waves. The model is able to represent strong downslope flows and recirculating flow regions (rotors) generated by the mountainous region located upwind of the airport. Comparisons of model predictions against LIDAR traces indicate that the model replicates wind shear for 50% of cases where it was recorded, although the location and magnitude of the wind shear usually differs between the modelled and measured datasets; the lack of agreement is likely to be because the input meteorological conditions are not wholly representative of the upstream conditions and the LIDAR trace does not exactly coincide with the aircraft trajectory. When airports are located in hilly terrain, near‐ground flow features such as wind shear and turbulence periodically cause disruption to aircraft movements. The FLOWSTAR model has been configured to represent favourable and unfavourable landings at Hong Kong International Airport; the model predicts high wind shear at some locations along the flight path (black dotted line). Quantitative analyses of wind shear generated as a result of wind veering and backing demonstrate the importance of flow features such as trapped lee waves. [ABSTRACT FROM AUTHOR]

Methods for now-casting adverse weather conditions with the potential to cause disruption to aircraft landings often make use of real-time measurements at high temporal resolution. This paper describes processing methodologies developed to derive meteorological parameters from such measurements recorded in the vicinity of Hong Kong International Airport, specifically a radiometer in King's Park, a wind profiler and surface anemometer on Cheung Chau Island and weather buoys in the Pearl River estuary. These parameters are suitable for use as input to a now-casting application of the computationally efficient airflow model, FLOWSTAR, which has previously been shown to predict mountain waves generated by flow over Lantau Island to the southeast of the airport. Radiosonde data from King's Park have been used to test the radiometer processing method; the novel approach of using minimum and maximum potential temperature deviations from a series of height-dependent linear profiles to derive radiometer inversion layer parameters generates data that compares well with values derived from corresponding radiosonde profiles. Mountain wave strength depends on the magnitude of wind speed in the inversion layer; wind profiler data can be used to estimate typical and maximum wind speeds and associated wind directions using estimates of inversion layer depth derived from the radiometer data. With estimates of surface sensible heat flux appropriate for the airport's coastal location calculated using a marine boundary layer scheme, a dataset of meteorological parameters at 20-min resolution has been derived for input into the FLOWSTAR model. The combination of automated meteorological data processing methods and flow field modelling has the potential to form part of a now-casting system for determining strong wind shear conditions at the airport. [ABSTRACT FROM AUTHOR]