Research On Airport Slant Visibility Inversion Of Lidar

Visibility is one of the most common and important meteorological factors that affect civil aviation flight safety.Visibility can be divided into horizontal visibility and slant visibility in civil aviation applications.At present,the transmissometer used in Chinese civil aviation airports can only measure the horizontal visibility around the runway area.However,for the takeoff and landing of the aircraft,the pilots focus more on the slant visibility.Slant visibility and horizontal visibility have great difference under some weather conditions.If the airport lets in or lets pass the aircraft only according to horizontal visibility,it will have serious impact on the safety of the takeoff and landing of the aircraft.Lidar has good spatial and temporal resolution and high sensitivity.It can inverse aerosol extinction coefficient and calculate the slant visibility by lidar echo signal.However,it is difficult to calculate aerosol lidar ratio and the boundary value of aerosol extinction coefficient,which are two important parameters that influence the inversion accuracy.Firstly,an algorithm based on Fernald-PSO method is proposed to calculate aerosol lidar ratio and the boundary value of aerosol extinction coefficient at the same time.Secondly,the validity of the algorithm is verified by the data of lidar and AERONET,and the influence of aerosol lidar ratio on the slant visibility under different weather conditions is analyzed.Then,the joint detection of airport visibility is carried out by using lidar and transmissometer,and the variation characteristics of the slant visibility and horizontal visibility of airport under different weather conditions are investigated.The results show that aerosol lidar ratios calculated by using this algorithm are different under different weather conditions.The aerosol lidar ratios in cloudy and sunny days are smaller than the assumed value of 50 sr,and that in shower days are larger.For the same signal,the larger the difference between the assumed values and calculated values of aerosol lidar ratio,the greater the absolute value of relative errors of aerosol extinction coefficient and slant visibility.The maximal errors are 18.93% and 19.90%,respectively.In order to reduce the inversion error of aerosol extinction coefficient and improve the calculation accuracy of slant visibility,it is necessary to use the calculated value of aerosol lidar ratio instead of the assumed value in the process of solution.In addition,the slant visibility and horizontal visibility of airport are different under different weather conditions.Therefore,for the safety of civil aviation flight and the efficiency of airport operation,it is essential to use lidar and transmissometer for the joint detection of slant visibility and horizontal visibility in airport.