First triple-wavelength lidar observations of depolarization and extinction-to-backscatter ratios of Saharan dust

Abstract

Abstract. Two Saharan dust layers observed over Leipzig in February and March 2021 were used to provide the first ever lidar measurements of the extinction coefficient at 1064 nm for desert dust. The advanced multiwavelength Raman polarization lidar was able to provide, for the first time, the lidar ratio (extinction-to-backscatter ratio) and particle linear depolarization ratio at all three classical lidar wavelengths (355, 532 and 1064 nm). The pure dust conditions during the first event exhibit lidar ratios of 47±8, 50±5 and 63±13 sr and particle linear depolarization ratios of 0.260±0.026, 0.298±0.017 and 0.214±0.025 at the wavelengths of 355, 532 and 1064 nm, respectively. The second, slightly polluted dust case shows a similar spectral behavior with values of the lidar ratio of 52±8, 47±5 and 61±10 sr and the depolarization ratio of 0.188±0.053, 0.270±0.017 and 0.242±0.007 at 355, 532 and 1064 nm, respectively. The results were compared to AERONET v3 inversions and GRASP retrievals at six and seven wavelengths, which could reproduce the spectral slope of the lidar ratio from 532 to 1064 nm. The spectral slope of the particle linear depolarization ratio could not be reproduced by the AERONET inversions, especially at 1064 nm.

Investigating the dependence of mineral dust depolarization on complex refractive index and size with a laboratory polarimeter at 180.0° lidar backscattering angle

“…The spectral dependence of the dust lidar PDR is indeed instructive (Burton et al, 2016;Haarig et al, 2022;Miffre et al, 2020). Outlooks of this work are obviously also interesting, as underscored by recent papers (Kahnert et al, 2020;Luo et al, 2022), discussing the ability of the spheroidal model to mimic light scattering by complex-shaped mineral dust.…”

“…In this paper, accurate values (< 1 %) of the dust lidar PDR are provided from a laboratory π -polarimeter operating at 180.0 • lidar exact backscattering angle and at 355, 532 nm wavelengths to account for the importance of the spectral dependence of the lidar PDR to better constrain lidar inversions and aerosol typing (Burton et al, 2016;Haarig et al, 2022). Since the scattering angle and the wavelengths are determined for lidar purposes, we here investigate the dependence of the mineral dust lidar PDR on the dust particles size and complex refractive index (CRI), the latter being particularly important as related to light absorption.…”

ALiDAn: Spatiotemporal and Multiwavelength Atmospheric Lidar Data Augmentation

“…Such databases may also be useful for locations without a sunphotometer. Wavelength-related statistics of D LR,Å obtained over long periods [80], [98], [99] can expand data on aerosols, in particular advanced analysis at 1064nm [100].…”