Mechanisms of synoptic circulation patterns influencing winter/spring PM_2.5 concentrations in South Korea

This study comprehensively analyzes the spatiotemporal distribution of the meteorological variables and large-scale atmospheric patterns that produce high concentrations of particulate matter with aerodynamic diameters below 2.5 μm (PM_2.5) in South Korea. Through self-organizing map (SOM) analysis of upper-level geopotential height fields and aerosol optical depth (AOD), the recurring coupled patterns of the large-scale circulation and the AOD are classified into three clusters associated with high pollution episodes that frequently occur in spring and winter. In addition, the long-range transport is investigated for each SOM type using the Hybrid Single-Particle Lagrangian Integrated Trajectory model, which provides a comprehensive understanding of the factors influencing PM_2.5 levels. An analysis of frequency shows an increasing trend in one of the three spring patterns. Results from the Coupled Model Intercomparison Project Phase 6 indicate a continued increase in frequency for the aforementioned pattern with rising surface temperatures. Our findings underscore the importance of understanding synoptic-scale effects on PM_2.5 variability to inform mitigation strategies in the context of climate change.