Sensitivity of in-situ trace gas profiles to air traffic and local urban sources as seen by MOZAIC and DISCOVER-AQ

Since the mid-90's the MOZAIC (Measurements of OZone, water vapor, carbon monoxide, and nitrogen oxides by in-service AIrbus airCraft) program has been providing vertical profiles of reactive gases into and out of major airports. In 2001, NOy instruments were added to the aircraft providing a means to assess the influence of aircraft traveling along constant flight corridors. Recent interest in using MOZAIC data to validate air quality models such as CMAQ raises questions regarding the suitability of the data for this purpose. Specifically, to what degree are aircraft data influenced by aviation emissions versus local pollution along approach and departure flight paths at lower altitudes. From 2002-2004, there were 14 flights into Dulles International Airport with available NOy measurements. Additional profiles with similar characteristics are available from airports along the eastern seaboard. Appropriate data for comparison with these profiles has become available with the recent completion of phase-I of DISCOVER-AQ (Deriving Information on Surface conditions from Column and VERtically resolved observations relevant to Air Quality) during which the NASA's P-3B aircraft performed over 250 profiles, including one landing at the Baltimore Washington International Airport. These profiles offer comparative observations of O3, CO, and reactive nitrogen both near and away from major air traffic patterns in the Baltimore-DC region. Similarities and differences in the MOZAIC and DISCOVER-AQ data sets are assessed to evaluate their sensitivity to emission from air traffic versus local urban sources. Acknowledging the lack of temporal overlap in the two datasets, historical surface measurements will also be used to estimate any temporal trends related to changing emission levels.