Hong Kong Observatory currently uses a series of meteorological instruments, including long-range LIDAR (light detection and ranging) systems, to provide alerting services of low-level windshear and turbulence for Hong Kong International Airport. For some events that are smaller in spatial dimensions and are rapidly changing, such as low altitude windshear and turbulence associated with buildings or man-made structures, it would be necessary to involve meteorological instruments that offer greater spatial resolution. Therefore, the Observatory has set up a short-range LIDAR on the roof of the AsiaWorld-Expo during the summers over the past several years, conducting field research on the feasibility of strengthening early alerting for windshear and turbulence over the north runway’s eastern arrival runway (Runway 25RA) and developing an automated early alerting algorithm. This paper takes the pilot reports for Runway 25RA during the 2013 field research as verification samples, using different thresholds for radial wind velocity spatial and temporal changes detected by the short-range LIDAR to calculate the relative operating characteristic (ROC) curve, and analyzes its early alerting performance.

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The quality and applications of vertical velocity data from SODAR and radar wind profilers are examined in this paper. The vertical velocity data from collocated SODAR and boundary layer type wind profilers are compared for a period of 7 months. It is found that the two datasets are well correlated, but the slope of the linear fit to the data has a significant deviation from 1. This may be related to the difference in the sampling volumes of the vertical beams from the two instruments. The correlation for horizontal wind data was found to be much stronger. Three applications of the vertical velocity data are discussed: subsidence in the outer periphery of a tropical cyclone and in hazy weather, and the upward motion of the air in convective weather. Data such as those under study here are found to contribute significantly to the monitoring and understanding of weather conditions, and would be useful for the nowcasting of lowvisibility and convective weather.