Integration of Airborne and Ground Observations of Nitryl Chloride in the Seoul Metropolitan Area and the Implications on Regional Oxidation Capacity During KORUS-AQ 2016

摘要: Abstract. Nitryl chloride ( ClNO2 ) is a radical reservoir species that releases chlorine radicals upon photolysis. An integrated analysis of the impact on regional photochemistry in Seoul metropolitan area (SMA) during Korea–United States Air Quality Study (KORUS-AQ) 2016 field campaign presented. Comprehensive multiplatform observations were conducted aboard NASA DC-8 and at two ground sites (Olympic Park, OP; Taehwa Research Forest, TRF), representing an urbanized forested suburban region, respectively. Positive correlations between daytime Cl2 observed both sites, slope which was dependent O3 levels. The possible mechanisms are explored through box model simulations constrained with observations. overall diurnal variations appeared similar but nighttime systematically different. For about half observation days OP site level increased sunset rapidly decreased around midnight. On other hand, high levels throughout night TRF site. Significant for 4–5 h after sunrise. Airborne observations, calculations, back-trajectory consistently show these morning likely from vertical or horizontal transport air masses west. Box results chlorine-radical-initiated chemistry can by elevating net chemical production rates ozone ∼25  % morning.