Research On The Method Of Visibility Inversion Based On Lidar Joint Detection

My country’s air transportation industry is developing rapidly,and the research of aviation meteorology is also more important and urgent.As one of the important parameters in the field of aviation meteorology,visibility has a very important impact on civil aviation flight safety.The detection principle of horizontal visibility near the ground is relatively simple and easy to implement.The aircraft takes off and landing in a slope direction and has a certain slope angle to the horizontal.The accuracy of slope visibility during takeoff and landing is more meaningful than horizontal visibility.However,due to the different distribution of aerosol extinction coefficients at different vertical heights,it is difficult to detect the visibility of the slope.Master the detection method of slope visibility,improve the accuracy of inversion and predict the accuracy of weather changes,and provide a safety foundation for civil aviation.Lidar has the advantages of good temporal and spatial resolution and high measurement sensitivity.Using atmospheric attenuation characteristics to detect scattered signal power can achieve inversion of slope visibility.Horizontal visibility is highly controllable by instruments near the ground,and the distribution of extinction coefficients at any height in the slope direction is difficult to be accurate.Joint lidar detection will be used to obtain slope visibility,especially for flights with low visibility.In low-visibility weather such as sand,dust,and haze,the multiple scattering effects of lasers and aerosols are serious,which may lead to large slope visibility errors.In order to accurately invert the slope visibility,this thesis first explored the working principle of lidar and the basic equation of inversion visibility,and obtained the slope direction visibility inversion method used in this paper.Secondly,an improved algorithm for inverting slope visibility by lidar equation when affected by multiple scattering is proposed.A new scattering phase function is fitted according to the backscatter peak value,and the influence factors of the multiple scattering correction factor m are explored.Based on the relationship with changes,the profile distribution of aerosol extinction coefficient in different weather conditions is analyzed,and the oblique range visibility is solved.Finally,based on the problem of the difficulty in determining the boundary value of the extinction coefficient in the detection method based on the slope visibility,the dual-light source digital camera and the multiple reflectometer are used to verify the accuracy of the sub-level visibility in both directions,and the former is used as the slope extinction coefficient boundary value.Lidar retrieves the slope visibility at different times and uses night-time detection data to verify it,providing a new method for joint inversion of slope visibility.The research results show that in low-visibility weather,as the transmission distance increases,the correction factor m shows a proportional trend.The slope visibility is inverted by the fitted scattering phase function,especially in the haze weather,the slope visibility contrast error is as much as 10.9%.Using the method of digital camera and lidar joint detection,the observation errors of the three types of weather are calculated to be within a reasonable range,which verifies the rationality of the joint detection method of oblique visibility at night,especially to provide better safety guarantee for night-flight flights.