Response in ozone and methane to small emission changes and dependence on cruise altitude

Within the scope of the LEEA (Low Emissions Effect Aircraft) project the effects of small changes in aircraft NOX emissions on CH4-NOX-O3 chemistry were systematically investigated with the ultimate objective to develop a parametric relationship between the amount / altitude / location of emissions and their effect on the climate system. A large number of sensitivity experiments were carried out with the global 3D CTM p-TOMCAT. Aircraft emission data was used from the European AERO2k Global Aviation Emissions Inventory for 2002. In the experiments the standard emission profile was altered such that, within discrete cruise altitude bands in the altitude range 5–15 km, emissions were globally increased by 5–20%. Investigation of ozone precursor concentrations, ozone production efficiency and methane lifetime has shown both highly linear and additive behaviour in the atmospheric response to the emission perturbations that were applied. This suggests that in future a linear parameterisation can be used to predict the effects of small emission changes on the chemistry in the UTLS region. The LEEA project was funded by Airbus UK and the Department for Trade and Industry.