AVIATION FUEL TRACER SIMULATION - MODEL INTERCOMPARISON AND IMPLICATIONS

An upper limit for aircraft-produced perturbations to aerosols and gas eous exhaust products in the upper troposphere and lower stratosphere (UT/LS) is derived using the 1992 aviation fuel tracer simulation perf ormed by eleven global atmospheric models. Key findings are that subso nic aircraft emissions: 1) have not be responsible for the observed wa ter vapor trends at 40 degrees N; 2) could be a significant source of soot mass near 12 km, but not at 20 km, 3) might cause a noticeable in crease in the background sulfate aerosol surface area and number densi ties (but not mass density) near the northern mid-latitude tropopause, and 4) could provide a global, annual mean top of the atmosphere radi ative forcing up to +0.006 W/m(2) and -0.013 W/m(2) due to emitted soo t and sulfur, respectively.