DeLiAn – a growing collection of depolarization ratio, lidar ratio and Ångström exponent for different aerosol types and mixtures from ground-based lidar observations

Abstract

Abstract. 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.

Aircraft Engine Dust Ingestion at Global Airports

“…A fixed lidar ratio of 44 sr is used to convert the measured dust attenuated backscatter coefficient profiles to extinction coefficient profiles (Kim et al, 2018, Young et al, 2018. This lidar ratio value is in agreement with the averaged ground-based lidar ratio measurements for desert dust, recently reported by (Floutsi et al, 2022), despite the regional dependence. L2 data are averaged and quality controlled to produce the L3 product, which provides monthly mean extinction profiles as a function of aerosol type (Tackett et al, 2018).…”

“…Through the sum of these signals, the profile of 'pure-dust' backscatter coefficient at 532 nm. A region-specific lidar ratio (see supplement for values) is then used to calculate 'pure-dust' extinction coefficient profiles from the backscatter coefficient profiles (Amiridis et al, 2015;Marinou et al, 2017;Proestakis et al, 2018;Floutsi et al, 2022). Here we use the LIVAS 'pure dust extinction coefficient product' for cloud-free, night-time cases, on an identical 2°×5° grid to match the CALIOP L3 data, for the years 2007 to 2019.…”

“…In Amiridis et al, 2013;Marinou et al, 2017;Proestakis et al, 2018;Floutsi et al, 2022), see supplement). Amiridis et al (2013) showed that the two products are not similar over the Sahara desert and Europe, with differences occurring due to both different lidar ratios and how different aerosol types are accounted for.…”

“…Both lidar datasets are dependent on a choice of lidar ratio to convert measured attenuated backscatter signal into extinction coefficient (44 Sr for CALIOP L3, regionally varying for LIVAS). In reality the lidar ratio will vary spatially with dust optical properties (Schuster et al, 2012;Floutsi et al, 2022). This contributes to differences between LIVAS and CALIOP L3.…”

Correlation between marine aerosol optical properties and wind fields over remote oceans with use of spaceborne lidar observations

“…but are all in the standard deviation ranges. According toBohlmann et al (2018),Groß et al (2011),Groß et al (2015), andFloutsi et al (2022), the pure mar LR at 355 nm can vary from 10 sr to 40 sr, with the average of around 20 sr, thus it is considered that the averaged mar LR in this study are reasonable. At the middle wind speed range (marine aerosol particles might be broken up into smaller ones with a wind speed increase At the very high wind speed (>16 1 ms −  ) above the SP area and the SI area, the marine aerosol particle size variations turn out to a stable state along with the wind speed.…”