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 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.

Tropospheric sulfate from Cumbre Vieja volcano at Las Palmas, transported towards Cabo Verde – lidar measurements of aerosol extinction, backscatter and depolarization at 355, 532 and 1064 nm

“…The corresponding mean values are summarized in Table 1. In the lofted layer, the mean lidar ratio between 1.3 and 5.3 km of 58.4 and 47.3 sr (at 355 and 532 nm) and the particle linear depolarization ratio of 24.5, 28.1 and 24.1 % (at 355, 532 and 1064 nm) are in a typical range for desert dust (Haarig et al, 2017;Floutsi et al, 2023). In the PBL, relatively clean marine conditions (Bohlmann et al, 2018) were observed, which were characterized by a mean lidar ratio of 17.4 and 23.7 sr (at 355 and 532 nm) between 0.25 and 0.6 km and a mean particle linear depolarization ratio of 0.7, 1.1 and 1.0 % (at 355, 532 and 1064 nm) between 0.06 and 0.6 km.…”

Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS): The European Research Infrastructure Supporting Atmospheric Science

“…Recently, quality-controled 20-year climatological datasets were released. These datasets have been widely used to identify aerosol types and respective optical properties (Papagiannopoulos et al, 2018), infer microphysical properties through inversion techniques (Müller et al, 2016), increase optical information through lidar/photometer synergies (Chaikovsky et al, 2016), study aerosol hygroscopicity (Bedoya-Velásquez et al, 2018) and aerosol-cloud interactions (Mamouri and Ansmann, 2017;Marinou et al, 2019), optimize satellite product retrievals (Amiridis et al, 2013;Nicolae et al, 2018;Floutsi et al, 2023) e. ACTRIS as a tool for monitoring extreme events and atmospheric hazards ACTRIS data have been widely used to characterize specific or extreme events affecting the atmosphere either caused by natural or human-induced phenomena. The capacity to be operational 24/7 at most of the Observational Platforms has been essential on many occasions over the past decade.…”

Assessing Lidar Ratio Impact on CALIPSO Retrievals Utilized for the Estimation of Aerosol SW Radiative Effects across North Africa, the Middle East, and Europe

“…DeLiAn (Depolarization ratio, Lidar ratio, and Ångström exponent) is a newly developed dataset providing aerosol-speciated properties acquired using ground-based lidars operated in experimental campaigns (e.g., SAMUM 1/2, SALTRACE) or contribute to networks (e.g., EARLINET) [67,70,71,74,[108][109][110][111][112][113][114][115][116][117][118][119][120][121][122][123][124][125][126][127]. Ship-borne vertically resolved aerosol measurements in the Atlantic Ocean have been also obtained using Lidars mounted on the Meteor and the Polastern research vessels [72,[128][129][130][131].…”

“…The separation of the aerosol load on its counterparts within a layer is made according to Equation ( 5) by setting depolarization ratios equal to 0.28 and 0.03 for the dust (δ d ) and non-dust components (δ nd ), respectively. The depolarization values have been extracted from the DeLiAn dataset [74]. Based on Equation ( 5), the dust backscatter coefficient (β d ) is obtained, contributing to the total measured amount (β p ), whereas the portion of the backscattered signal attributed to nondust particles is calculated via the subtraction of these two terms (Equation ( 6)).…”

“…Ground-based lidars have provided unprecedented LR measurements [60,62,[67][68][69][70][71][72][73] thanks to their advanced observational capabilities. A comprehensive overview of these measurements is presented by [74], who developed the DeLiAn database containing state-of-the-art observations acquired using ground-based lidars operating in different regions of the planet (in terms of aerosols' regime).…”