The impact of nitrogen oxides emissions from aircraft upon the atmosphere at flight altitudes—results from the aeronox project

Abstract

The AERONOX project investigated the emissions of nitrogen oxides (NO x ) from aircraft engines and global air traffic at cruising altitudes, the resultant increase in NO x concentrations, and the effects on the composition of the atmosphere, in particular with respect to ozone formation in the upper troposphere and lower stratosphere. The project was structured into three subprojects: Engine exhaust emissions, physics and chemistry in the aircraft wake, and global atmospheric model simulations. A complementary program of work by aviation experts has provided detailed information on air traffic data which was combined with data on aircraft performance and emissions to produce a global emissions inventory. This summary gives an overview of the results of this project. Further details are given in the following papers of this issue and the final project report of 1995. The work resulted in improved predictive equations to determine NO x emissions at cruise conditions based on available data for aircraft/engine combinations, and NO x emission measurements on two engines in cruise conditions. This information was combined with a traffic database to provide a new global NO x emissions inventory. It was found that only minor chemical changes occur during the vortex regime of the emission plume; however, this result does not exclude the possibility of further changes in the dispersion phase. A variety of global models was set up to investigate the changes in NO x concentrations and photochemistry. Although aviation contributes only a small proportion (about 3%) of the total global NO x from all anthropogenic sources, the models show that aviation contributes a large fraction to the concentrations of NOX in the upper troposphere, in particular north of 30°N.