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>Smoke of extreme Australian bushfires observed in the stratosphere over Punta Arenas, Chile, in January?2020: optical thickness, lidar ratios, and depolarization ratios at 355 and 532nm
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Smoke of extreme Australian bushfires observed in the stratosphere over Punta Arenas, Chile, in January?2020: optical thickness, lidar ratios, and depolarization ratios at 355 and 532nm
We present particle optical properties of stratospheric smoke layers observed with multiwavelength polarization Raman lidar over Punta Arenas (53.2°S, 70.9°W), Chile, at the southernmost tip of South America in January?2020. The smoke originated from the record-breaking bushfires in Australia. The stratospheric aerosol optical thickness reached values up to 0.85 at 532nm in mid-January?2020. The main goal of this rapid communication letter is to provide first stratospheric measurements of smoke extinction-to-backscatter ratios (lidar ratios) and particle linear depolarization ratios at 355 and 532nm wavelengths. These aerosol parameters are important input parameters in the analysis of spaceborne CALIPSO and Aeolus lidar observations of the Australian smoke spreading over large parts of the Southern Hemisphere in January and February?2020 up to heights of around 30km. Lidar and depolarization ratios, simultaneously measured at 355 and 532nm, are of key importance regarding the homogenization of the overall Aeolus (355nm wavelength) and CALIPSO (532nm wavelength) lidar data sets documenting the spread of the smoke and the decay of the stratospheric perturbation, which will be observable over the entire year of 2020. We found typical values and spectral dependencies of the lidar ratio and linear depolarization ratio for aged stratospheric smoke. At 355nm, the lidar ratio and depolarization ratio ranged from 53 to 97sr (mean 71sr) and 0.2 to 0.26 (mean 0.23), respectively. At 532nm, the lidar ratios were higher (75–112sr, mean 97sr) and the depolarization ratios were lower with values of 0.14–0.22 (mean 0.18). The determined depolarization ratios for aged Australian smoke are in very good agreement with respective ones for aged Canadian smoke, observed with lidar in stratospheric smoke layers over central Europe in the summer of 2017. The much higher 532nm lidar ratios, however, indicate stronger absorption by the Australian smoke particles.
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