Photochemical variations of climatically significant gases in transport aircraft emission plumes

The effective emission index (EEI) for a gas is defined as the product of t he index of its transformation in plume (ITP) and the given emission index (EI). The EI is the ratio of the gas mass in the nozzle section to the mass of fuel that is burned (in g/kg). The ITP is the ratio of the number of mo lecules of NOx, NOy constituents, ozone, and CO formed in the emission plum e of combustion products to that emitted into the plume per unit length of its axis. The EEI is designed for estimating (1) the effect of plume photoc hemical processes on the total mass of combustion products emitted into the atmosphere and (2) the impact of these products on the earth's ozone layer . Formulas for computing the ITP are obtained using the earlier-described p hotochemical box model for processes in a plume and the ambient air. In cal culations, published data of aircraft measurements of trace gases along bas ic Northern-Hemisphere flight corridors of the world transport aircraft are used. The ITPs of nitrogen oxides, nitric acid, and ozone are estimated fo r January and July at 30 degrees and 50 degrees N, both inside and outside of the corridors (as well as for flights in both the lower stratosphere and the upper troposphere). The dependences of the ITP on the reference emissi on time and ambient air temperature are considered.