Long-range transport of short-lived nitrogen dioxide in East Asia

Abstract

This study explores the broader spatial influence of nitrogen dioxide (NO₂) over East Asia by integrating satellite and aircraft observations with chemical transport and trajectory model analyses. Tropospheric NO₂ column densities observed by the TROPOspheric Monitoring Instrument (TROPOMI) over the Yellow Sea—located between China and South Korea—are found to be 3.2 times higher in winter than the annual average, highlighting the role of prevailing westerlies in facilitating regional-scale transport during the cold season. Additional insights into the diurnal dynamics of NO₂ transport are provided by hourly observations from the Geostationary Environment Monitoring Spectrometer (GEMS). To further examine the mechanisms responsible for this transport, satellite-based evidence is complemented by in situ aircraft measurements and chemical transport model simulations. Aircraft profiles over the Yellow Sea confirm that NO₂ can be extensively transported at altitudes of 1–2 km under favorable meteorological conditions. Model results indicate that the lifetime of NOₓ in major urban areas—such as the Beijing–Tianjin–Hebei region and the Seoul Metropolitan Area—can be extended from several hours to 1–3 days, depending on meteorological conditions. Trajectory analyses further suggest that NOₓ originating from East Asia can reach downwind regions across adjacent seas within 12–24 h. These findings underscore the importance of accounting for the long-range transport of short-lived pollutants in the development of national air quality management strategies. © 2025 The Authors