The Precise Detection Of Aerosol Particle Size Distributions Of Fog/haze In The Open Atmosphere

In recent years,fog/haze weather occurs frequently,which has a great impact on the atmospheric environment and human race.The influence of fog/haze on the environment is mainly due to the physical and optical properties of atmospheric particles.Therefore,it is necessary to detect particle size distributions when fog/haze weather occurs in the open atmosphere.Aiming at the shortcomings of the current detecting methods of particle size distributions of fog/haze in the open atmosphere,this paper proposed a new method for simultaneous measurements of fog particles and aerosols by using wide-spectrum/multi-wavelength extinction and small-angle forward scattering data.The key detection techniques of particle size distributions of fog particles and aerosols in the open atmosph ere were studied.It mainly consists of two parts.First is the design of the key parameters of the detection system.Second is the simulation and verification of measurement.The key parameters in our measurement are the forward scattering angle and detection wavelength.According to the theory of Mie scattering,the sensitivity between the scattering phase function of different angles and the 12 particle size distributions are calculated.The forward detecting angle is determined to be 0-1.1°.Then,1.1°is selected as the forward scattering angle according to the overlapping area of scattering phase function of different angles and the particle size distributions of multiple types.According to the particle size reflected by the kernel functions of different wavelengths,the optimal wavelengths of our system are selected.The regularization algorithm for the inversion of particle size distributions of tog droplets and aerosols is established.The algorithm are simulated and tested by aerosol particle size distributions of three types and fog droplet size distributions.The microphysical parameters including complex refractive index,volume concentration,number concentration and et al.are also inverted.The results show that the inversion of complex refractive index is precise.The maximum inversion error of the particle size distributions can be controlled within 40%,and the average error within 12%.The stability of algorithm is also analyzed.The results show that when the error is introduced within 1%for each channel,the error of the aerosol size distribution is within 30%;when the error is introduced within 0.5%for each channel,the error of the fog droplet size distribution is within 30%.At the same time,the inversions of aerosol particle size distributions measured in different weather are also simulated.Finally,the influence of the initial complex refractive index on the particle size distributions is discussed.It is concluded that the imaginary part of the complex refractive index had a great influence on the inversion results.Finally,the improved regularization algorithm based on wide-spectrum/multi-wavelength extinction+small-angle forward scattering data proposed in this paper can realize high-precision detection of aerosol particle size distribution when fog/haze weather occurs without changing the atmospheric environment.