The present-day and future impact of NOx emissions from subsonic aircraft on the atmosphere in relation to the impact of NOx surface sources

摘要

The effect of present-day and future NOemissions from aircraft on the NO and ozone concentrations in theatmosphere and the corresponding radiative forcing were studied using athree-dimensional chemistry transport model (CTM) and a radiative model. Theeffects of the aircraft emissions were compared with the effects of the threemost important anthropogenic NO surface sources: road traffic,electricity generation and industrial combustion. From the model results, NOemissions from aircraft are seen to cause an increase in the NO andozone concentrations in the upper troposphere and lower stratosphere, and apositive radiative forcing. For the reference year 1990, the aircraft emissionsresult in an increase in the NO concentration at 250 hPa of about 20ppt in January and 50 ppt in July over the eastern USA, the North AtlanticFlight Corridor and Western Europe, corresponding to a relative increase ofabout 50%. The maximum increase in the ozone concentrations due to the aircraftemissions is about 3-4 ppb in July over the northern mid-latitudes,corresponding to a relative increase of about 3-4%. The aircraft-induced ozonechanges cause a global average radiative forcing of 0.025 W/m inJuly. According to the ANCAT projection for the year 2015, the aircraft NOemissions in that year will be 90% higher than in the year 1990. As aconsequence of this, the calculated NO perturbation by aircraftemissions increases by about 90% between 1990 and 2015, and the ozoneperturbation by about 50-70%. The global average radiative forcing due to theaircraft-induced ozone changes increases by about 50% between 1990 and 2015. Inthe year 2015, the effects of the aircraft emissions on the ozone burden andradiative forcing are clearly larger than the individual effects of the NOsurface sources. Taking chemical conversion in the aircraft plume into accountin the CTM explicitly, by means of modified aircraft NO emissions, asignificant reduction of the aircraft-induced NO and ozoneperturbations is realised. The NO perturbation decreases by about40% and the ozone perturbation by about 30% in July over Western Europe, theeastern USA and the North Atlantic Flight Corridor. Atmospheric composition and structure(troposphere · composition and chemistry) · Meteorology and atmosphericdynamics (radiative processes)