Abstract
The use of Raman and high-spectral lidars enables measurements of a stratospheric aerosol extinction profile independent of backscatter, and a multi-wavelength (MW) lidar can obtain additional information that can aid in retrieving the microphysical characteristics of the sampled aerosol. The inversion method for retrieving aerosol particle size distributions and microphysical particle parameters from MW lidar data was studied. An inversion algorithm for retrieving aerosol particle size distributions based on the regularization method was established. Based on the inversion of regularization, the inversion method was optimized by choosing the base function closest to the aerosol distribution. The logarithmic normal distribution function was selected over the triangle function as the base function for the inversion. The averaging procedure was carried out for three main types of aerosol. The 1% averaging result near the minimum of the discrepancy gave the best estimate of the particle parameters. The accuracy and stabilization of the optimized algorithm for microphysical parameters were tested by scores of aerosol size distributions. The systematic effects and random errors impacting the inversion were also considered, and the algorithm was tested by the data, showing 10% systematic error and 15% random error. At the same time, the reliability of the proposed algorithm was also verified by using the aerosol particle size distribution data of the aircraft. The inversion results showed that the algorithm was reliable in retrieving the aerosol particle size distributions at vertical heights using lidar data.
Highlights
Aerosols play an important role in the Earth’s radiation budget [1,2,3,4]
Aerosol sounding with Raman lidar and high-spectral-resolution lidar (HSRL) has emerged in recent years as a powerful tool that can provide comprehensive and quantitative information on aerosol properties at a vertically resolved scale [7,8,9,10,11]
Deriving the aerosol size distribution (ASD) and microphysical aerosol quantities from the extinction and backscattering coefficients is a classic example of an ill-posed mathematical problem that is typical in Earth sciences [12]
Summary
Aerosols play an important role in the Earth’s radiation budget [1,2,3,4]. The vertical distribution of aerosols is a critical issue in estimating aerosol radiative forcing and its associated climate impacts [5]. Multi-wavelength lidars have the ability to invert the measurements to provide vertical profiles of particle physical properties. The regularization algorithm is used most commonly for inverting multi-wavelength measurements [6], allowing the retrieval of particle size, concentration, and to some extent the main features of the particle size distribution. Using the regularized inversion algorithm, the particle size distribution and microphysical parameters of aerosols are obtained without assuming the initial complex refractive index and aerosol distribution. D. Pérez-Ramírez et al [17] analyzed the effects of systematic and random errors on particle microphysical properties from multi-wavelength lidar measurements using an inversion with regularization. The optical parameter at multi-wavelengths of 355 nm, 532 nm, and 1064 nm were built using the aerosol distribution measured by the airborne particle size spectrometer, and the simulated distributions were retrieved using the algorithm. The results showed that the aerosol microphysical parameters at vertical altitude could be retrieved reliably using the optimized algorithm
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