Aircraft pollution – a futuristic view

[摘要] Impacts of NO_x, H₂O and aerosol emissions from a projected2050 aircraft fleet are investigated using the Oslo CTM2,with emissions provided through the EU project SCENIC.The aircraft emission scenarios consist of emissions from subsonic andsupersonic aircraft.In particular it is shown that aerosol emissions from such anaircraft fleet can have a relatively large impact on ozone, andpossibly reduce the total atmospheric NO_x by more than what isemitted by aircraft.Without aerosol emissions this aircraft fleet leads to similar NO_xincreases for subsonic (at 11–12 km) and supersonic (at 18–20 km)emissions, 1.35 ppbv and 0.83 ppbv as annual zonal means, respectively.H₂O increases are also comparable at these altitudes: 630 and599 ppbv, respectively.Tropospheric ozone increases are about 10 ppbv in the NorthernHemisphere due to emissions from subsonic aircraft.Increased ozone loss from supersonic aircraft at higher altitudesleads to ozone reductions of about 39 ppbv in the Northern Hemisphereand 22 ppbv in the Southern Hemisphere.The latter reduction is a result of transport of ozone depleted airfrom northern latitudes.When including aircraft aerosol emissions, NO_x is reduced due toheterogeneous chemistry. The reduced NO_x seems to counterweight thereduction of ozone from emissions of NO_x and H₂O above 20 km.At these altitudes the NO_x (and thus ozone loss) reduction is largeenough to give an aircraft emissions induced increase in ozone.In the height range 11–20 km altitude, however, ozone production isreduced. Heterogeneous reactions and reduced NO_x enhances ClO,further enhancing ozone loss in the lower stratosphere.This results in a 14 ppbv additional reduction of ozone.Although supersonic aircraft have opposite effects on ozone in theupper and lower stratosphere, the change in ozone columns is clearlydominated by the upper stratospheric loss, thus supersonic aircraftaerosol emissions lead to enhanced ozone columns.The largest increase in the ozone column due to aerosol emissions istherefore seen in the Northern Hemispheric autumn and winter, givinga column increase of 4.5 DU.It is further found that at high northern latitudes during spring theheterogeneous chemistry on PSCs is particularly efficient, therebyincreasing the ozone loss.

[学科分类] 大气科学