Investigating the link between mineral dust hematite content and intensive optical properties by means of lidar measurements and aerosol modelling

Abstract. This study investigates the relationship between lidar-measured intensive optical properties of Saharan dust and simulated hematite content, using data collected during the Joint Aeolus Tropical Atlantic Campaign (JATAC) in 2021 and 2022. Measurements were taken in Mindelo, São Vicente, Cabo Verde. The study aims to determine how variations in hematite content influence the intensive optical properties of dust particles, particularly in the ultraviolet-visible (UV-VIS) spectrum. Given the well-documented impact of hematite on the extinction properties of dust, especially absorption in the UV-VIS range, our hypothesis is that these effects will be detectable in lidar measurements. Specifically, this study focuses on the lidar ratio, particle depolarization ratio and backscatter- and extinction-related Ångström exponents at 355 nm and 532 nm wavelengths. By analyzing dust plume cases separately regarding their size differences, the strongest positive correlation was identified between the backscatter-related Ångström exponent and hematite fraction (r=0.87, p=0.02). These findings contribute to improving the representation of dust in atmospheric models and refining calculations of its direct radiative effect, which often overlook the variability in mineralogical composition in their dust descriptions.