Inversion with regularization for the retrieval of tropospheric aerosol parameters from multiwavelength lidar sounding

Abstract

We present an inversion algorithm for the retrieval of particle size distribution parameters, i.e., mean (effective) radius, number, surface area, and volume concentration, and complex refractive index from multiwavelength lidar data. In contrast to the classical Tikhonov method, which accepts only that solution for which the discrepancy reaches its global minimum, in our algorithm we perform the averaging of solutions in the vicinity of this minimum. This averaging stabilizes the underlying ill-posed inverse problem, particularly with respect to the retrieval of number concentration. Results show that, for typical tropospheric particles and 10% error in the optical data, the mean radius could be retrieved to better than 20% from a lidar on the basis of a Nd:YAG laser, which provides a combination of backscatter coefficients at 355, 532, and 1064 nm and extinction coefficients at 355 and 532 nm. The accuracy is improved if the lidar is also equipped with a hydrogen Raman shifter. In this case two additional backscatter coefficients at 416 and 683 nm are available. The combination of two extinction coefficients and five backscatter coefficients then allows one to retrieve not only averaged aerosol parameters but also the size distribution function. There was acceptable agreement between physical particle properties obtained from the evaluation of multiwavelength lidar data taken during the Lindenberg Aerosol Characterization Experiment in 1998 (LACE 98) and in situ data, which were taken aboard aircraft.

Microphysical characterization of long-range transported biomass burning particles from North America at three EARLINET stations

“…This method has been developed in the framework of EAR-LINET (Müller et al, 2016) and is based on explicitly solving the mathematical equations that relate the particle microphysical and optical properties by means of regularization techniques, an approach that is shared with Müller et al (1999) and Veselovskii et al (2002) inversion algorithms. That means that forward computations using tables containing microphysical versus optical properties are not carried out, having the advantage that particle size distribution shape is not assumed as input, but approximately calculated as output.…”

Separation of the optical and mass features of particle components in different aerosol mixtures by using POLIPHON retrievals in synergy with continuous polarized Micro-Pulse Lidar (P-MPL) measurements

“…the column-integrated aerosol extinction. These two parameters can be estimated by or recalculated from the output of lidar stand-alone algorithms such as Müller et al (1999), Veselovskii et al (2002) or Böck-mann et al (2005) which employ state-of-the-art elasticRaman lidar measurements at several wavelengths. Such advanced measurements are scarce, however, compared with the large database of elastic lidar measurements worldwide.…”

Lidar Measurements of Canadian Forest Fire Smoke Episode Observed in July 2013 over Warsaw, Poland

“…Also the calibrated depolarization profiles at 355 and 532nm were calculated [8]. In the near future, we plan to perform also the retrieval of micro-physical properties of aerosols for characteristic layers found for different periods of the event [9].…”