Effect of plume processes on aircraft impact

A versatile Gaussian plume model has been developed and used to investigate the chemistry in expanding aircraft plumes for a wide range of conditions, including the plume expansion rate, the composition of the background atmosphere, and the total time of the plume integration. The dependence of plume processing on altitude, latitude and season has been investigated in order to generate plume parameterizations for use in global models. Two different parameterizations have been compared. The results of the two parameterizations have been incorporated into a global model to assess the importance of plume processing on calculated aircraft impact. In contrast to a previous plume study, which found reductions of 20–35% in aircraft‐induced NOx at cruise altitude and 10–12% smaller column ozone changes at northern midlatitudes when plume effects were incorporated, results from the present study suggest that plume processing has only a small effect on the calculated aircraft impact on ozone at subsonic cruise altitudes. Both plume parameterizations gave small changes in ozone perturbations, suggesting that differences between previous modeling studies are not due primarily to the different parameterizations used in those studies.