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This study analyzed the PM 10 aerosol enhancement caused by East Asian atmospheric warming during transboundary transport in March of 2021. It was found to be cooled near the north polar area and to have shifted the polar vortices northward over the East Asian region in the mid-troposphere. The Siberian high was weakened and the East Asian region was characterized by a positive air temperature anomaly and negative zonal wind speeds. The increasing rate of air temperature anomalies at 2 m was higher in the high latitude areas over 40°N in Mongolia and northeastern China, causing a decrease in zonal wind speeds at 10 m over eastern China and Korea. The anomalous variations of the MODIS-induced aerosol optical depth (AOD) were found to be positive with the highest value of +0.93 in the area ranging from northeastern China to Korea, despite the recent decreasing trends. The positive anomalous region of the MODIS-induced AOD was correlated with positive air temperatures and negative zonal wind speeds, causing enhanced formations of secondary aerosols in the atmosphere. As cold northerly winds were suppressed in the East Asian region, anomalous high pressures (anticyclonic anomalies) developed frequently in eastern China and moved to Korea. The Weather Research and Forecasting model to which meteorological and climate data were applied coupled with Chemistry (WRF-Chem) simulations on increases in the PM 10 enhancement ratio, indicating enhanced formation amounts, during transboundary transport for the period of March 13–15, 2021. An air mass near the high terrain surface over eastern China under the backward side of an anticyclone warmed and moved toward the relatively low terrain of the Yellow Sea and Korea in keeping with the height. Air temperature inversion developed in the anomalous warmer center in the mid-troposphere, reaching the surface of the Yellow Sea and Korea. High PM 10 concentrations were constrained near the shallow inversion layer. Furthermore, the PM 10 enhancement ratio showed a positive level over the Yellow Sea with nearly zero anthropogenic emissions on the surface, gradually increasing at a rate of approximately 60% in Korea. The hourly contribution by the warming-induced PM 10 enhancement (PM 10 CbWIE) was calculated and found to be at the highest level of 70% in Seoul, Korea. Among PM 10 secondary inorganic aerosols, nitrate formations were enhanced during transboundary transport in the warming-induced anticyclone with reactions rich in ammonium. While the sulfate enhancement ratio reached a positive level over the Yellow Sea, the gradual decrease during transboundary transport may be reflected by the decreased emissions of sulfur dioxide in eastern China. • PM10 aerosol enhancement caused by atmospheric warming during transboundary transport. • Anomalous variations of the aerosol optical depth from northeastern China to Korea. • Meteorological and climate data-applied WRF-Chem simulations in the East Asian region. • Enhanced formations of PM10 secondary aerosols in the warming-induced anticyclone. [ABSTRACT FROM AUTHOR]

The particulate matter (PM 10) trend has decreased at a growing rate in South Korea, which is on the downwind side in the East Asian region over the last five-year period of 2014–2018. Nevertheless, nationwide, days of high PM 10 levels and haze frequently occurred over the period of February–March in 2019. During the period of February–March 2019, two major atmospheric blockings were identified over the Alaskan region in the northeast Pacific over the periods of February 21-March 1 and March 18–29. Warm and stagnant synoptic meteorological conditions favorable for high-PM 10 haze days in the East Asian region were accompanied 4–5 days later by the remote Alaskan atmospheric blockings. The Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) was used, applying zero-out emission to analyze the regional PM 10 contribution on severe haze days exceeding a daily average of 100 μg m−3 over South Korea during March 3–6, 2019. The daily average regional PM 10 contribution indicated a rate of 57% compared to rates of 23% before and 29% after severe haze days. Furthermore, the major regional PM 10 components were nitrates (49%), other inorganics (28%), and sulphates (9%) during the severe haze days. Among inorganic PM 10 aerosols, other inorganics mainly composed of anthropogenic fine dust were not a major contribution component in the South Korean case due to fuel consumption changes in China. However, higher nitrate flux from sources in eastern China remained in South Korea, though in slightly reduced amounts. The contribution rate of NO X discharged from automobiles has gradually increased in China, and the level of SO 2 remained on a low level through emission control technologies and regulatory options. The warm and stagnant atmosphere in the East Asian region caused the flux of relatively more nitrates were likely transported, with ammonium nitrate in the atmosphere and with lower sulphate levels. • Warm and stagnant conditions favorable for haze were accompanied by blocking 4–5 days later. • WRF-Chem was used, applying zero-out emission to analyze regional PM10 contribution. • Regional PM10 contribution indicated 57% compared to 23% before and 29% after haze. • The warm and stagnant atmosphere caused the flux of more nitrates likely transported. [ABSTRACT FROM AUTHOR]