# Study of the Algorithm for Wind Shear Detection with Lidar Based on Shear Intensity Factor
## 1 Introduction
For the F-factor algorithm, they found the relationship between the vertical wind speed and the wind speed gradient along the slide path through mathematical derivation and eliminated the vertical wind speed term. The results revealed that the modified F-factor algorithm has a better detection performance for small-scale wind shear. However, the determination of the alarm threshold still needs further research. For the Plane Position Indicator (PPI) scanning mode of lidar, [PERSON] et al. proposed the gradient search alerting algorithm of low-level wind shear based on a spatial adaptive scale [16]. The core idea of this algorithm is to calculate the velocity gradient based on several spatial adaptive scales, with the best fitting scale depending on the wind shear intensity factor. The results demonstrated that the algorithm could detect wind shear of all spatial scales and improve the alarm rate. [PERSON] et al. [17] designed a new slide path wind shear detection algorithm based on the PPI scanning method of lidar and improved the calculation of wind profile along the slide path. Results showed that their algorithm could successfully identify low-level wind shear, achieving a 94% alerting rate compared to 88% for the conventional ramp detection algorithm based on the same dataset. However, their algorithm has still not improved the extension and contraction strategy of ramp length. In conclusion, the currently proposed wind shear alerting algorithms can be divided into two main types. One uses the correlation factors of wind shear, such as the F-factor algorithm and eddy dissipation rate, to monitor wind shear. Another directly monitors the wind field data's intensity and wind shear location based on the concept of wind shear itself. To accurately determine the intensity and location information of wind shear, this paper improved the ramp extension and contraction strategy in the ramp detection algorithm based on the wind shear intensity factor and tested the effectiveness of the improved algorithm by numerical simulation. Due to the complicated weather during wind shear, it is difficult to directly measure the real intensity and location of wind shear. Therefore, the wind shear data in the pilot's report are generally used as the true values. However, the pilot's report is subjective and the wind shear event is generally found afterwards, so data from the pilot's report are usually inaccurate, meaning the wind shear intensity depends on this subjective judgment. At the same time, if wind shear is detected at the airport, the aircraft is usually not allowed to take off and land. So, the wind shear data in the pilot'sreport are very limited. Therefore, simulating the wind shear wind fields to verify the effectiveness of wind shear detection algorithms is necessary. This paper is organized as follows. Section 2 describes the methods used for the working principle of conventional and improved algorithms and the technical process of the paper. Section 3 discusses the numerical simulated experiments and presents the results. The final section (Section 4) provides discussion and presents the conclusions.