Simulation Analysis And Experimental Method Study On Optical Properties Of Haze Considering Multiple Scattering

Haze has become a research hotspot in the field of atmospheric science in China because of its complex components and strong harmfulness.Multiple scattering plays an important role in the study of haze optical properties.However,the effect of multiple scattering is generally ignored in the experimental study,which leads to large inversion error.In view of this,the theoretical analysis and experimental method research on the optical properties of haze considering multiple scattering are of great significance and application prospect.The optical properties of haze under single scattering condition are analyzed based on Mie scattering theory.In a typical haze event,the extinction coefficient and scattering coefficient of haze are 1.2 km-1 and 0.98 km-1 respectively.The forward,lateral and backward differential scattering coefficients are 0.168 km-1sr-1,0.069 km-1sr-1 and 0.0196 km-1sr-1 respectively.Based on Monte Carlo Method Simulation,the optical properties of haze are analyzed when multiple scattering is considered.In this case,the extinction coefficient of haze is at least 13%lower than that of single scattering when multiple scattering is considered.Only the first three scattering effects need be considered when the multiple scattering of haze is studied.According to the law of laser beam propagation and scattering in the haze,an experimental method is designed to study the optical properties of the haze considering multiple scattering by using Raman scattering of nitrogen molecules and multi-field detection technique.This method can not only be used for retrieving extinction coefficient of haze accurately when multiple scattering is considered,but also can be used to study the mathematical relationship between the scattering coefficient and the field of view.Aiming at achieving the proposed experimental method,the haze optical characteristic experimental system is designed based on optical absorption cell.The resolution of the system for detecting the increment of Raman scattering signal of nitrogen molecules is 1.52×10-9 W.The resolution for detecting the increment of Mie scattering coefficient is 0.52×10-11 m-1sr-1.The relative error of extinction coefficient is less than 12%when the SNR of Raman scattering signal is more than 53,which proves the validity of the system.In this paper,the theoretical analysis and experimental method research on haze optical properties are carried out,and the experimental system and data inversion method are designed to study haze optical properties considering multiple scattering.The research results verify the feasibility of the system.The research contents have important research significance for the precise calibration of detection data such as sun photometers and Lidar,the fine inversion retrieving of the microphysical properties of haze and the study of the radiation transmission model of haze.