Model calculations of the impact of NOx from air traffic, lightning, and surface emissions, compared with measurements

The impact of NOx from aircraft emissions, lightning, and surface contribut ions on atmospheric nitrogen oxides and ozone in the North Atlantic flight corridor has been investigated with the three-dimensional global chemistry transport model TM3 by partitioning the nitrogen oxides and ozone according to source category. The results have been compared with Pollution from Air craft Emissions in the North Atlantic flight corridor (POLINAT 2) and Subso nic Assessment Ozone and Nitrogen Oxide Experiment (SONEX) airborne measure ments in the North Atlantic flight corridor in 1997. Various cases have bee n investigated: measurements during a stagnant anticyclone and an almost cu toff low, both with expected high aircraft contributions, a southward bound flight with an expected strong flight corridor gradient and lightning cont ributions in the south, and a transatlantic flight with expected boundary l ayer pollution near the U.S. coast. The agreement between modeled results a nd measurements is reasonably good for NO and ozone. Also, the calculated i mpact of the three defined sources was consistent with the estimated exposu re of the sampled air to these sources, obtained by specialized back trajec tory model products. Model calculations indicate that aircraft contributes 55% to the mean NOx concentration and 10% to the O-3 concentration in the N orth Atlantic flight corridor in October 1997, whereas lightning and surfac e emissions add 15% and 25% to the NOx concentration and 20% and 30% to the O-3 concentration.