Lidar For Low-level Wind Shear Identification And It's Application In Aviation Meteorology

Low level wind shear is recognized as an air stealth killer,which is a serious threat to flight safety,especially in the take-off and landing phase of aircraft.However,lidar can provide high spatial and temporal resolution of low altitude three-dimensional wind field information,which is a new method to detect low-level wind shear.At present,the research on the use of lidar to identify low-level wind shear is still in its infancy,so it is great significance to study the identification algorithm of low-level wind shear.This paper,we use the lidar dataset which were collected at Kunming Changshui international Airport of china from December 2015 to April2016 and at northeast of China in July to September 2015.Firstly,we use the K-neighborhood frequency method to control the quality of lidar data.Then,in order to test the detection performance of lidar,wind measurements from a Chinese new all-fiber coherent lidar were compared with double theodolite Pibal and wind profile radar.Based on the above work,we design a low altitude wind shear identification algorithm by using least squares fitting method and determine the low-level wind shear warning thresholds and key monitoring areas by combining low altitude windshear weather characteristics and aircraft landing safety standards.Finally,real examples are used to test the effect of shear alarm system.The conclusions are as follows:(1)Low-level wind shear can destroy the balance of aircraft and affect the flight(1)Low-level wind shear can destroy the balance of aircraft and affect the flight safety by affecting the lift and drag of flight.Low level wind shear can be caused by strong convective weather,frontal system,inversion layer,jet stream,and ground obstacles.Lidar is good at detecting dry wind shearhe which are caused by inversion layer,jet stream,and ground obstacles.(2)K-domain frequency method can effectively filter the noise echo and fill the missing values.According to the characteristics of the lidar data,we design a setof comparative experiments to get the optimal parameter configuration,which can suppression of noise and filling of missing values but can't change the radial velocity of pulsation.(3)By comparing correlation,standard deviation and mean deviation of lidar?WPR and balloon under different weather types.The results show: Under clear-air,cloudy,foggy and hazy conditions,the wind lidar is more accurate than wind profiler with a half standard deviation of horizontal wind.During precipitation,available detection range of wind lidar is limited due to signal attenuation,the maximum observable altitude decreases to be only half of the wind profiler.On the whole,lidar's results are more stable than the wind profiler's.The dataset correlation coefficient between lidar and radiosonde can reach up to more than0.9.Above all conditions,the accuracy of lidar and wind profiler will both be affected by the variation of wind speed,meanwhile,the change trends are different as the wind speed increase.(4)Based on the meteorological characteristics of low altitude wind shear,a synthetic shear identification algorithm based on least squares linear fitting is designed which can effectively identify the low-level wind shear.We determine the low-level wind shear warning thresholds and key monitoring areas by combining low altitude windshear weather characteristics and aircraft landing safety standards.(5)As for the 30 Wind shear sample,the algorithms could identified out 20,hit rate is 66.7%,only 16 cases ware identified by L.M Wind Analyer lidar,hit rate is53.33%,the recognition effect is better than that of Wind Analyer radar.13 clear Wind shear sample,the algorithms could identified out 11,hit rate is 84.61%,L.M Wind Analyer lidar could identified out 9,hit rate is 69.23%,all are far higher than other weather types of hit rate.Therefore,lidar is more suitable for detecting clear type wind shear.(6)The water vapor molecular content,rain intensity,aerosol concentration and ground cover could cause lidar transmission attenuation,which will affect the wind shear identification effect of the algorithm in this paper and the Wind Analyer radar algorithm.