Vertical profiling and aerosol typing using fluorescence Raman and depolarization lidar measurements over Thessaloniki, Greece

Abstract. In this study, we present the first fluorescence lidar observations over Thessaloniki, Greece, (40.63° N, 22.96° E; 60 m a.s.l.) using a multiwavelength Raman and depolarization lidar with fluorescence capabilities. For the first time in the Eastern Mediterranean fluorescence backscattering coefficient and the spectral fluorescence capacity parameter are retrieved and combined with particle depolarization ratio, lidar ratios, and Ångström exponents to characterize the aerosol load over Thessaloniki, a region influenced by diverse aerosol sources. Representative case studies of biomass-burning smoke, Saharan dust, and mixed pollen event showing distinct fluorescence properties are discussed in detail, while an extended dataset covering the period April 2024 – December 2025 is further analysed, comprising 108 aerosol layers from 50 measurement cases. A sub-dataset is also compared with the EARLINET Mahalanobis distance–based typing algorithm, highlighting the importance and complementarity of fluorescence lidar observations on the aerosol characterization in complex environments. Based on the spectral fluorescence capacity and the particle depolarization ratio, the identified layers are classified into smoke, dust, polluted continental, clean continental and mixed pollen. THELISYS retrievals show that the spectral fluorescence capacity depends on aerosol type, with smoke showing the highest values (3.5 × 10⁻⁶ − 12.7 × 10⁻⁶ 𝑛𝑚⁻¹), followed by mixed pollen (2.3 × 10⁻⁶ − 4.8 × 10⁻⁶ 𝑛𝑚⁻¹), polluted continental (1.0 × 10⁻⁶ − 3.3 × 10⁻⁶ 𝑛𝑚⁻¹), clean continental (0.3 × 10⁻⁶ − 1.2 × 10⁻⁶ 𝑛𝑚⁻¹) and dust (0.6 × 10⁻⁶ − 1.3 × 10⁻⁶ 𝑛𝑚⁻¹). The fluorescence capacity values observed for all aerosol types are comparable with other studies across central and northern Europe, however the linear particle depolarization ratio measurements attributed to pollen differ from those reported at more northern latitudes, possibly reflecting differences in pollen type.