Inversion of vertical mass concentration of non-spherical aerosols using multi-wavelength lidar

Abstract. A method of inversion the vertical mass concentration of non-spherical aerosols is proposed in this paper and the effect of particle shape, complex refraction index and wavelength on the inversion is investigated. The experiment of multi-wavelength polarized lidar indicates that the aerosols with depolarization ratios of 0.22–0.37 have non-spherical characteristics. Given the non-spherical character of dust aerosols, the optical properties with different shapes, wavelengths, and complex refraction index are calculated using discrete dipole approximation. Based on previous studies, dust aerosol particles were assumed to be ellipsoidal and rectangular in this study. In several non-spherical shapes we studied, it found that when the shape parameter of non-spherical particles is D=1 rectangular, the mass concentration difference between non-spherical and spherical aerosol is the largest, and the maximum difference can reach 19.08 %. It was found that in the detection of aerosol mass concentration by multi-wavelength lidar, the larger the wavelength, the smaller the aerosol mass concentration. It was also found that the larger the real part of the complex refraction index, the smaller the mass concentration and the smaller the maximum difference between the three wavelengths. The vertical mass concentrations inversed using this method are 2.83 mg/m³, 2.51 mg/m³, and 4.2 mg/m³ at 2:03, 7:28, and 12:36 on March 16, 2021, at the altitude of 1.5 km respectively. The inverted vertical mass concentrations were compared with the near-ground monitored at the observatory. The results show that there is same correspondence between the changes in aerosol mass concentrations near the ground and at high altitudes at the same moment.