Saharan and Arabian dust optical properties registered by sun photometry during A-LIFE field experiment in Cyprus

Abstract

The A-LIFE (Absorbing aerosol layers in a changing climate: aging, lifetime, and dynamics) field experiment, conducted in Cyprus in April 2017, employed a wide range of ground-based and airborne instruments, including passive/active remote sensing and in-situ techniques. This study presents the columnar records obtained by sun photometry. Two sun/sky/lunar photometers, belonging to AERONET network, were strategically placed at two sites: Pafos and Limassol, 40 km apart. Aerosol optical and microphysical properties derived from direct sun and sky radiance measurements are analysed to determine an inventory of aerosol event days during the experiment, with mineral dust being present in nearly 75 % of days. Ångström exponent values obtained from 1020 and 1640 nm channels (0.5 for Saharan dust and 0.34 for Arabian dust) can be served as a classification criterion. Dust sources are key point for a well understanding of the size distribution and absorption power. According to columnar records, Saharan dust exhibited less absorbing particles. The columnar volume efficiency factor (linear fit between aerosol optical depth and total volume concentration) was proved as a reliable proxy for the identification of dust origin since Arabian and Saharan dusts exhibit different slopes: 1.28 and 1.68 µm2 µm−3, respectively. Analysing all the inversion products mixtures of mineral dust were mainly dominated by Arabian dust, while mixtures of fine and coarse aerosols showed no clear prevalence of dust origin. No significant presence of black carbon-rich aerosols was detected in the atmospheric column, as absorption Ångström exponent values ranged from 1.6 to 3 across aerosol types identified.