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From 19 September to 13 December 2021, volcanic eruptions took place at the Cumbre Vieja ridge, Las Palmas, Canary Islands. Thereby, fine ash and volatiles, like sulfur dioxide (SO2), were emitted and transported over hundreds to thousands of kilometers away from the island. Continuous lidar observations with the multiwavelength-Raman-polarization lidar PollyXT were performed at the Ocean Science Center at Mindelo, Cabo Verde, in the framework of the Joint Aeolus-Tropical Atlantic Campaign (JATAC) 2021/2022 enabling the characterization of the atmospheric state above Mindelo during the eruption period. A special feature of the system operated at Mindelo is, that measurements of the particle extinction coefficient, the particle extinction-to-backscatter ratio (lidar ratio) and the particle linear depolarization ratio are available at all three wavelengths (355, 532 and 1064 nm). The typical aerosol conditions over Mindelo are a clean marine planetary boundary layer (PBL) up to approx. 1 km and above a Saharan dust layer (SAL, up to 6 km) during northern hemispheric summer and fall. A particle extinction coefficient smaller than 200 Mm−1, a lidar ratio smaller than 30 sr and a particle linear depolarization ratio close to 0 % have been typically observed within the planetary boundary layer, while a lidar ratio between 40 and 60 sr and a linear depolarization ratio between 20 and 30 % are characteristic for the SAL above. In contrast, during the time of the volcanic eruptions, a strongly polluted PBL was observed on specific days beginning on the 23 September 2021, whereby the particle extinction coefficient and the lidar ratio increased up to 800 Mm−1 and 80 sr (at 355 nm), respectively. On 24 September, the aerosol optical depth, determined by an AERONET (Aerosol Robotic Network) sun photometer, was as high as 0.9 and 1.1 (daily averages at 500 and 340 nm). HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) trajectories indicate air mass transport from Canary Islands to Mindelo at heights below 2 km. The observed pollution in the PBL over Mindelo is attributed to sulfate aerosol from the volcanic eruption at Las Palmas as the particle linear depolarization ratio was low (≤ 3 %) and, thus, does not indicate non-spherical particles, such as Saharan dust or volcanic ash. We thus conclude that sulfate aerosol formed from gaseous precursors during the transport (2–3 days for a distance of 1500 km) from Las Palmas towards Cabo Verde. No indications of volcanic ash over Mindelo were found in the SAL. This finding is supported by the HYSPLIT trajectories, which show that air masses in higher altitudes originate from the African continent and not from the Canary Islands. [ABSTRACT FROM AUTHOR]

This paper presents a collection of lidar-derived aerosol intensive optical properties for several aerosol types, namely the particle linear depolarization ratio, the extinction-to-backscatter ratio (lidar ratio) and the Ångström exponent. The data collection, named DeLiAn, is based on globally distributed, long-term, ground-based, multiwavelength, Raman and polarization lidar measurements, conducted mainly with lidars that have been developed at the Leibniz Institute for Tropospheric Research. The intensive optical properties are presented at two wavelengths, 355 and 532 nm, for 13 aerosol categories. The categories cover the basic aerosol types (i.e., marine, pollution, continental European background, volcanic ash, smoke, mineral dust), as well as the most frequently observed mixtures they form. This extensive collection also incorporates more peculiar aerosol categories, including dried marine aerosol that, compared to marine aerosol, exhibits a significantly enhanced depolarization ratio (up to 15 %). Besides Saharan dust, additional mineral dust types related to their source region were identified due to their lower lidar ratios (Central Asian and Middle Eastern dust). In addition, extreme wildfire events (such as in north America and Australia) emitted smoke into the stratosphere showing significantly different optical properties, i.e., high depolarization values (up to 25 %), compared to tropospheric smoke. The data collection reflects and underlines the variety of aerosol mixtures in the atmosphere and can be used for the development of aerosol-typing schemes. The paper contains the most up-to-date and comprehensive overview of optical properties from aerosol lidar measurements and, therefore, provides a solid basis for future aerosol retrievals in the frame of both spaceborne and ground-based lidars. Furthermore, DeLiAn can assist the efforts for the harmonization of satellite records of aerosol properties performed at different wavelengths. [ABSTRACT FROM AUTHOR]

This paper presents a collection of lidar-derived aerosol intensive optical properties for several aerosol types, namely the particle linear depolarization ratio, the extinction-to-backscatter ratio (lidar ratio) and the Ångström exponent. The data collection, named DeLiAn, is based on globally distributed, long-term, ground-based, multiwavelength, Raman and polarisation lidar measurements, conducted mainly with lidars that have been developed at the Leibniz Institute for Tropospheric Research. The intensive optical properties are presented at two wavelengths, 355 and 532 nm, for 13 aerosol categories. The categories cover the basic aerosol types (i.e., marine, pollution, continental European background, volcanic ash, smoke, mineral dust) as well as the most frequently observed mixtures they form. This extensive collection also incorporates more peculiar aerosol categories, including dried marine aerosol that, compared to marine aerosol, exhibits a significantly enhanced depolarization ratio (up to 15 %). Besides Saharan dust, additional mineral dust types related to their source region were identified due to their lower lidar ratios (Central Asian and Middle Eastern dust). In addition, extreme wildfire events (such as in north America and Australia) emitted smoke into the stratosphere showing significant different optical properties, i.e., high depolarization values (up to 25 %), compared to tropospheric smoke. The data collection reflects and underlines the variety of aerosol mixtures in the atmosphere and can be used for the development of aerosol typing schemes. The paper contains the currently most comprehensive overview of optical properties from aerosol lidar measurements and, therefore, provides a solid basis for future aerosol retrievals in the frame of both spaceborne and ground-based lidars. Furthermore, DeLiAn can assist the efforts for harmonization of satellite records of aerosol properties performed at different wavelengths. [ABSTRACT FROM AUTHOR]