The Development And Applications Of A No-Blind-Zone Dual FOV Lidar

Lidar,as one kind of active remote sensing methods for the aerosols,has the advantage of high temporal and spatial resolution.However,due to the effect of geometric overlap factor(GOF)in traditional Mie lidars,large dead zone and transition zone causes disadvantages of the detection of lower atmosphere.In this study,the lower atmospheric aerosols in level and vertical direction have been observed based on the dual field of view(FOV)technique and a new algorithm exploration.The detail introduction of optical design,structure design,electronic design in dual FOV lidar were given in this study.It demonstrated the joining method of the dual FOVs' signals,which not only realized the detection of high signal-to-noise ratio in the far field,but also ensured the detection of near-field with zero blind.The traditional Fernald method was applied in dual FOV lidar to explore the vertical distribution of aerosols.To retrieve the horizontal distributions of aerosols,a composition of the Fernald method and slope method was applied.So a priori assumptions of even atmospheric conditions and the already-known reference point in the lidar equation were avoided.The quality control(QC)technologies of dual FOV lidar were conducted to ensure the further field applications and operational applications.The zero blind zone detection of aerosol was verified in the balloon sounding experiment in Shanghai in 2018,which truly realized the accurate observation of aerosol in 0-1000 m of the lower atmosphere.Field experiments with a range of 15 km and spatial resolution of 7.5 m were conducted to urban aerosol distribution.Through fitting between the mass concentration measured by surface air quality station(AQS)and the overhead aerosol extinction coefficient measured by lidar,a non-linear relationship was returned.Applied this non-linear relationship to lidar scanning,we obtained the mass concentration of PM10 distribution with radius of 5 km.Applied this dual FOV lidar to the vehicle platform,we overcome the periodic depolarization problem and realized the "walking and measuring" of aerosol spatial distribution.So,the effectiveness of the dual FOV lidar system has been verified by comparing with the surface particle measurements and the mobile experiments.In this way,it provided basis and technical support for the subsequent applications in lower atmosphere with this technology.