Low-Level Wind Shear Alerting Algorithm Research Of The Direct Detection LiDAR

Low-level wind shear is an internationally-accepted atmospheric phenomenon that seriously affects flight safety. There are several types of wind shear. Conducting warning for different types of low-level wind shear, flight safety can be improved effectively.Currently, the single ramp detection, as the only LiDAR alerting algorithm applied in practice, leads to false alerting easily. So it is very important to study deeply on the alerting algorithm. In addition to selecting the appropriate scanning mode to get effective wind speed data, the processing of wind speed data is also very important.Low-level wind shear occurs mainly during take-off departure and landing approach of the aircrafts. So the glide scanning has been chosen, with both pertinence and shorter scanning time. Thereby the rate of early alerting is improved. After determining the scanning mode, the radial wind speed data from the glide scanning need to go through quality control at first. The effective data should be selected and recombined, forming the recombinant headwind profile. Secondly, the alerting algorithm is used on the recombinant headwind profile to find the range and the strongest position of wind shear, which should be reported to pilots. There are mainly three alerting algorithms, including F factor, eddy dissipation rate and the ramp detection. According to the study of these three algorithms and experiments, the F factor and eddy dissipation rate algorithm need to go through a lot of experiments to determine the threshold, having major difficulties. The ramp detection has been applied in practice among the airport. Due to actual application, alerting rate has been greatly improved. A algorithm of combining glide scanning with both single and double ramp detection has been proposed. The algorithm detects the recombinant headwind profile on gradient changes of single and double ramps. Finally, wind shear threshold and intensity factor discriminant formula are used as reference to determine if wind shear appears. The effectiveness of this method has been proved by LiDAR measurement data. It is significant to improve the windshear alerting rate and practical application.