Mesoscale numerical investigations of air traffic emissions over the NorthAtlantic during SONEX flight 8: A case study

Chemical data from flight 8 of NASA's Subsonic Assessment (SASS) Ozone and Nitrogen Oxide Experiment (SONEX) exhibited signatures consistent with airc raft emissions, stratospheric air, and surface-based pollution. These signa tures are examined in detail: focusing on the broad aircraft emission signa tures that are several hundred kilometers in length. A mesoscale meteorolog ical model provides high-resolution wind data that are used to calculate ba ckward trajectories arriving at locations along the flight track. These tra jectories are compared to aircraft locations in the North Atlantic Flight C orridor (NAFC) over a 27-33 hour period. Time series of flight level NO and the number of trajectory/aircraft encounters within the NAFC show excellen t agreement. Trajectories arriving within the stratospheric and surface-bas ed pollution regions are found to experience very few aircraft encounters. Conversely, there are many trajectory/aircraft encounters within the two ch emical signatures corresponding to aircraft emissions. Even many detailed f luctuations of NO within the two aircraft signature regions correspond to s imilar fluctuations in aircraft encountered. These NO spikes are due to the superposition of 14 to 25 aircraft plumes transported to the DC-8 flight t rack during the previous 33 hours. Results confirm that aircraft emissions were responsible for two chemical signatures observed during SONEX flight 8 . They also indicate that high-resolution meteorological modeling, when cou pled with detailed aircraft location data, is useful for understanding chem ical signatures from aircraft emissions at scales of several hundred kilome ters.