Air quality-driven variability in lidar-derived atmospheric optical properties in major urban agglomerations in Poland

We investigate the lidar-derived optical properties of atmospheric aerosol particles in relation to the air quality monitoring data in four major and highly urbanized Polish agglomerations known for exceedances of permitted pollution thresholds. Measurements were conducted with the mobile ESA Mie-Raman lidar in three Polish cities: Zabrze, Krakow, and Wroclaw, and with ground-based PollyXT lidar in Warsaw. To preserve high temporal resolution and capture dynamic atmospheric changes, a special algorithm was employed to determine the optical properties of molecules, aerosols and clouds from lidar measurements. This algorithm enabled real-time aerosol classification in the Atmospheric Boundary Layer (ABL) under varying ground level P M 10 concentration measurements of state air quality monitoring. Results indicate that during periods of low P M 10 concentrations, the aerosol optical properties across all four locations exhibited consistency. The mean scattering ratios ( S R ) for Zabrze, Krakow, Wroclaw and Warsaw were 1.84 ± 0.57, 1.95 ± 0.63, 1.69 ± 0.51 and 2.62 ± 1.18 respectively; the color ratios ( C R ) were 2.70 ± 0.55, 2.65 ± 0.69, 2.26 ± 0.42 and 2.60 ± 1.07; and the particle depolarization ratios ( δ p ) were 4.87 ± 2.84, 4.13 ± 1.72, 5.55 ± 2.10 and 1.87 ± 1.62. These values suggest a dominance of small, spherical particles, likely representing a mixture of anthropogenic pollutants and smoke in the urban ABL. In contrast, distinct changes in optical properties were observed during high P M 10 episodes. S R changed by ＋15.2%, −9.7%, −14.2% and−2.7%; C R by −38.1%, −12.8%, ＋6.6% and −25.0%; and δ p by ＋148.9%, ＋43.6%, ＋56.4% and −4.28%, for Zabrze, Krakow, Wroclaw and Warsaw, respectively. These differences suggest varying aerosol types and sources during elevated pollution levels. Aerosol target classification performed for each high P M 10 episode, revealed different origin and type of aerosols among the cities. Our study demonstrates the utility of lidar-derived aerosol classification within the ABL for identifying air pollution characteristics and potential sources. The findings underscore the value of remote sensing techniques as a complementary tool for ground-based air quality assessments, leading to the development of more effective air pollution mitigation strategies for different locations.