Aircraft pollution: a futuristic view

O. A. Sovde (1) , M. Gauss (1) , I.S.A. Isaksen (1) , G. Pitari (2) , C. Marizy (3)

1 Department of Geosciences [Oslo]
2 Dipartimento di Fisica
3 Acoustics & Environment Departmemt

Impacts of NO_x, H₂O and aerosol emissions from a projected 2050 aircraft fleet, provided in the EU project SCENIC, are investigated using the Oslo CTM2, a 3-D chemical transport model including comprehensive chemistry for the stratosphere and the troposphere. The aircraft emission scenarios comprise emissions from subsonic and supersonic aircraft. The increases in NO_y due to emissions from the mixed fleet are comparable for subsonic (at 11–12 km) and supersonic (at 18–20 km) aircraft, with annual zonal means of 1.35 ppbv and 0.83 ppbv, respectively. H₂O increases are also comparable at these altitudes: 630 and 599 ppbv, respectively. The aircraft emissions increase tropospheric ozone by about 10 ppbv in the Northern Hemisphere due to increased ozone production, mainly because of subsonic aircraft. Supersonic aircraft contribute to a reduction of stratospheric ozone due to increased ozone loss at higher altitudes. In the Northern Hemisphere the reduction is about 39 ppbv, but also in the Southern Hemisphere a 22 ppbv stratospheric decrease is modeled due to transport of supersonic aircraft emissions and ozone depleted air. The total ozone column is increased in lower and Northern mid-latitudes, otherwise the increase of ozone loss contributes to a decrease of the total ozone column. Two exceptions are the Northern Hemispheric spring, where the ozone loss increase is small due to transport processes, and tropical latitudes during summer where the effect of subsonic aircraft is low due to a high tropopause. Aerosol particles emitted by aircraft reduce both aircraft and background NO_x, more than counterweighting the effect of NO_x and H₂O aircraft emissions in the stratosphere. Above about 20 km altitude, the NO_x (and thus ozone loss) reduction is large enough to give an increase in ozone due to aircraft emissions. This effect is comparable in the Northern and Southern Hemisphere. At 11–20 km altitude, however, ozone production is reduced due to less NO_x. Also ClONO₂ is increased at this altitude due to enhanced heterogeneous reactions (lowered HCl), and ClO is increased due to less NO_x, further enhancing ozone loss in this region. This results in a 14 ppbv further reduction of ozone. Mainly, this results in an increase of the total ozone column due to a decrease in ozone loss caused by the NO_x cycle (at the highest altitudes). At the lowermost latitudes, the reduced loss due to the NO_x cycle is small. However, ozone production at lower altitudes is reduced and the loss due to ClO is increased, giving a decrease in the total ozone column. Also, at high latitudes during spring the heterogeneous chemistry is more efficient on PSCs, increasing the ozone loss.

Domaines: Océan, Atmosphère

O. A. Sovde, M. Gauss, I.S.A. Isaksen, G. Pitari, C. Marizy. Aircraft pollution: a futuristic view. Atmospheric Chemistry and Physics Discussions, 2007, 7 (1), pp.2531-2560. ⟨hal-00328046⟩