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 (O 3 ). 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 , O 3 , 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 ‐O 3 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.