High-PM₁₀ concentration episodes in Seoul, Korea: Background sources and related meteorological conditions

This study examines the origin of and favorable meteorological conditions for high concentrations of particulate matter with a diameter <10 μm (PM₁₀) in Seoul, Korea, in conjunction with systematic PM₁₀ pathways. High-PM₁₀ episodes, defined as days in which the 24-h mean PM₁₀ exceeds 100 μg m^-3, occurred 254 times during the period 2001-2008. Based on back trajectory and clustering analyses, the background sources of the high-PM₁₀ in Seoul are categorized as external (176 episodes) and internal sources (78 episodes). The primary external sources include the industrial areas in inland China and the Gobi desert. The ratio of external to internal sources varies strongly according to the season, with highs in winter and spring and lows in summer. A composite analysis of meteorological factors for high-PM₁₀ episodes with respect to the two sources (i.e., external and internal) suggests that an anomalous high pressure over Korea accompanied by an anomalous low pressure over the source regions favors both upper-level transport from the external source regions and the local accumulation of atmospheric PM₁₀ in Seoul. The origins of high-PM₁₀ episodes and their associated meteorological conditions found in this study can provide theoretical underpinnings for dust control strategies.