Interannual variability over the eastern North Atlantic Ocean: chemical and meteorological evidence for tropical influence on regional-scale transport in the extratropics

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Observed boreal fall season (September-November) 1991 surface CO data from Mace Head, Ireland, are characterized by particularly high mixing ratios, as evidenced by high means, medians, and maxima for those months, relative to the same data for boreal fall 1992. Air parcels characterized by elevated CO during fall 1991 are attributed to European sources on the basis of isentropic back trajectory analysis. There is evidence of the existence of Rossby wave links with the tropical upper troposphere over South America and the central Pacific Ocean which are responsible for the climatic forcing giving rise to the observed interannual variation in large-scale flow patterns and influencing the chemical character of air parcels reaching Mace Head. Using CO as a tracer for short-lived continental anthropogenic O3 precursors and calculating ΔO3/ΔCO for air parcel trajectories following anticyclonic paths over western Europe during the late summer and fall season of 1991, we estimate O3 production over western Europe at about 66 (40-96) billion moles of O3 per summer (~3 Tg O3 per summer), based on 1985 CO emission inventory data (37 Tg CO yr-1 for western Europe). -Authors

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Journal of Geophysical Research