This thesis investigates the geometrical and optical properties of atmospheric aerosol layers over Thessaloniki during the period January 2023–May 2025, using an extensive dataset from the upgraded multi-wavelength Raman/Depolarization lidar system THELISYS and the Cimel sun/sky photometer, both operated by the Laboratory of Atmospheric Physics (LAP, AUTh). A total of 314 lidar profiles (235 daytime, 79 nighttime) were analyzed, after applying quality-control procedures to ensure validity and exclude profiles affected by clouds or signal disturbances. The Fernald–Klett and Raman inversion methods were implemented to derive aerosol optical parameters for daytime and nighttime measurements, respectively. Furthermore, the Wavelet Covariance Transform (WCT) technique was applied to extract the geometrical characteristics of the detected layers, including their base and top heights, thickness and center of mass. These properties provide a robust characterization of the vertical aerosol distribution over the Eastern Mediterranean, a region influenced by multiple natural and anthropogenic sources. The analysis focuses on specific optical properties—Lidar Ratio (LR), Particle Linear Depolarization Ratio (PLDR), and Backscatter Ångström exponent (BAE)—to classify aerosol types, trace their sources and assess their potential climate impacts. The retrieved properties were cross-compared with international literature and AERONET-based classifications to ensure consistency and reliability. The results show a dominance of urban and regional pollution aerosols, frequently mixed with Saharan dust, with strong seasonal variability. Spring and summer periods were marked by dust intrusions and biomass burning plumes, while autumn and winter were dominated by anthropogenic emissions. Case studies of extreme events, such as a biomass burning episode in August 2023 and a Saharan dust intrusion in May 2025, demonstrate the system’s enhanced capacity to monitor long-range transport phenomena and to capture the vertical structure of complex aerosol mixtures. Chapter 1 presents the basic characteristics of atmospheric aerosols and their possible climatic impact. Chapter 2 provides a brief description of the lidar technique and its application in aerosol studies. Chapter 3 describes the area of interest and the study period. It also presents in detail the upgraded Raman/Depol Lidar THELISYS and the Cimel photometer systems operating at LAP. Chapter 4 focuses on data processing and statistical analysis, highlighting seasonal variations, aerosol classification, and case studies of extreme transport events. Finally, Chapter 5 summarizes the main conclusions and discusses future perspectives for advancing aerosol monitoring This thesis investigates the geometrical and optical properties of atmospheric aerosol layers over Thessaloniki during the period January 2023–May 2025, using an extensive dataset from the upgraded multi-wavelength Raman/Depolarization lidar system THELISYS and the Cimel sun/sky photometer, both operated by the Laboratory of Atmospheric Physics (LAP, AUTh). A total of 314 lidar profiles (235 daytime, 79 nighttime) were analyzed, after applying quality-control procedures to ensure validity and exclude profiles affected by clouds or signal disturbances. The Fernald–Klett and Raman inversion methods were implemented to derive aerosol optical parameters for daytime and nighttime measurements, respectively. Furthermore, the Wavelet Covariance Transform (WCT) technique was applied to extract the geometrical characteristics of the detected layers, including their base and top heights, thickness and center of mass. These properties provide a robust characterization of the vertical aerosol distribution over the Eastern Mediterranean, a region influenced by multiple natural and anthropogenic sources. The analysis focuses on specific optical properties—Lidar Ratio (LR), Particle Linear Depolarization Ratio (PLDR), and Backscatter Ångström exponent (BAE)—to classify aerosol types, trace their sources and assess their potential climate impacts. The retrieved properties were cross-compared with international literature and AERONET-based classifications to ensure consistency and reliability. The results show a dominance of urban and regional pollution aerosols, frequently mixed with Saharan dust, with strong seasonal variability. Spring and summer periods were marked by dust intrusions and biomass burning plumes, while autumn and winter were dominated by anthropogenic emissions. Case studies of extreme events, such as a biomass burning episode in August 2023 and a Saharan dust intrusion in May 2025, demonstrate the system’s enhanced capacity to monitor long-range transport phenomena and to capture the vertical structure of complex aerosol mixtures. Chapter 1 presents the basic characteristics of atmospheric aerosols and their possible climatic impact. Chapter 2 provides a brief description of the lidar technique and its application in aerosol studies. Chapter 3 describes the area of interest and the study period. It also presents in detail the upgraded Raman/Depol Lidar THELISYS and the Cimel photometer systems operating at LAP. Chapter 4 focuses on data processing and statistical analysis, highlighting seasonal variations, aerosol classification, and case studies of extreme transport events. Finally, Chapter 5 summarizes the main conclusions and discusses future perspectives for advancing aerosol monitoring and climate-related applications.
Ευφροσύνη Ν. Κουτσαντά (2025) studied this question.