Height-Resolved Mechanisms of Carbonaceous Aerosols in Beijing: Two-Year Remote Sensing Revealing Season-Dependent Emission-Meteorology Interactions

The vertical distribution of carbonaceous aerosols critically influences their climate and health effects, yet long-term, height-resolved observations are lacking in Asia. Based on two years (2021–2022) of hourly vertical profiles retrieved from ground-based LiDAR in Beijing, we investigate the seasonal mechanisms governing the vertical variation of organic matter (OM) and black carbon (BC). We identify a pronounced vertical stratification: below 900 m, pollutants are dominated by easterly transport and suppression under high humidity in autumn/winter; at 900–1400 m, photochemical and aqueous oxidation peak in summer; above 1400 m, biomass burning (autumn/winter) and dust transport (spring) are prevalent. Primary and secondary organic carbon (POC and SOC) are separated at 750 m, contributing 63.4% and 36.6% to OM, respectively, with SOC maximizing at 900-1400 m. Random Forest-based meteorological normalization shows that emissions drive long-term trends, especially aloft. In contrast, meteorology primarily controls short-term variability and peaks; this occurs mainly through oxidation processes for OM and transport for BC. This study provides the first long-term vertical characterization of carbonaceous aerosols in Asia, with important implications for targeted pollution control.