Simultaneous Inversion of the Complex Refraction Index and the Particle Size Distribution of Nonspherical Aerosol Particles Using Latin Hypercube Sampling Method

The complex refraction index (CRI) and particle size distribution (PSD) are the most important microphysical properties of atmospheric aerosol. They play an important role in the light scattering characteristics of aerosol and atmospheric radiative forcing. Therefore, accurate and rapid inversion of the CRI and PSD of aerosols is very important to study the microphysical properties of aerosols and their effects on climate. Since most of the aerosol particles are nonspherical, the interaction between aerosol CRI and PSD makes it very difficult to invert aerosol CRI and PSD simultaneously. In order to solve the above problems, a method of simultaneous retrieval of aerosol CRI and PSD using Latin hypercube sampling (LHS) is proposed in this study. The T-matrix method is used to calculate the light scattering parameters of nonspherical aerosol particles, and the multi wavelength lidar is used to detect the extinction and backscattering parameters of aerosols. In this article, the LHS algorithm is used to sample real and imaginary parts of the aerosol CRI and the total number of particles, the median radius, and the mode width of the particle PSD. According to the sampling results, the aerosol optical parameters calculated by T-matrix are compared with those measured by the lidar system, and the root mean square error between them is calculated. The CRI and PSD of the actual aerosol are obtained by the successive approximation method. In this article, field experiments and sampling inversion are carried out at three different weather conditions. The result shows that the inversion of CRI is in accordance with the CRI of local typical aerosol types. The error between the inversion PSD and the measured PSD by particle spectrometer is all within 10%. The method proposed in this article for simultaneous inversion of aerosol CRI and PSD is of great practical value for further study of aerosol microphysical properties and their effects on climate.