SONEX airborne mission and coordinated POLINAT-2 activity: Overview and accomplishments

The SASS (Subsonic Assessment) Ozone and NO(x) Experiment (SONEX) was an airborne field campaign conducted in October-November 1997 in the vicinity of the North Atlantic Flight Corridor to study the impact of aircraft emissions on NO(x) and ozone (O₃). A fully instrumented NASA DC-8 aircraft was used as the primary SONEX platform. SONEX activities were closely coordinated with the European POLINAT-2 (Pollution from Aircraft Emissions in the North Atlantic Flight Corridor) program, which used a Falcon-20 aircraft. Both campaigns focused on the upper troposphere/'lowermost' stratosphere (UT/LS) as the region of greatest interest. Specific sampling goals were achieved with the aid of a state-of-the art modeling and meteorological support system, which allowed targeted sampling of air parcels with desired characteristics. A substantial impact of aircraft emissions on NO(x), O₃, and CN in the UT/LS of the study region is shown to be present. This mission provided direct support for the highly nonlinear nature of the NO(x)-O₃ chemistry. The results are being published in Special Sections of GRL and JGR. This overview provides a context within which these publications can be understood.