Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
However, soot
particles may act
as condensation
nuclei for sulfate
or other species,
modifying cirrus
clouds in the UT
or LS, and locally
they may be
important in the
destruction of O 3
(Bekki, 1997;
Lary et al., 1997).
Thus, we present
some estimates
of soot densities
and SADs for
future scenarios
to complement
those estimated
for the current
(1992) subsonic
fleet already
given in Chapter
3. There are large
uncertainties with
regard to the
sources and
distribution of
soot particles.
Emissions from
aircraft are
Figure 4-12: Annual average zonal mean change of ozone in the 30-
60°N latitude band for supersonic aircraft perturbations from AER-2D,
GSFC-2D, and UNIVAQ-2D models in (a) 2015 and (b) 2050. Model
scenarios are those passed through to Chapters 5 and 6.
particularly uncertain. Few global modeling studies are available for these aerosols (see Chapter 3 for details). Emissions of soot by aircraft [EI(soot)=0.03-0.4 g/kg]
(Friedl, 1997) have been studied by Bekki (1997), who used the Cambridge 2-D aerosol/soot model for past and present air traffic, and more recently by Rahmes et al.
(1998) for current and future aircraft fleets.
For the results presented herein, the aircraft-generated soot distribution was approximated by scaling the distribution of passive tracer calculated according to aircraft
fuel burn (see also Chapter 3). A number of models have calculated this distribution for 2015 and 2050 (1992 distribution is shown in Table 3-4); all show the largest
mass mixing ratio at about 12-km altitude and poleward of 40°N. The results for subsonic aircraft in the years 2015 and 2050 (IS92 Scenario 1) are shown in Table 4-
15. For 2015, some results are also included for subsonic and HSCT aircraft together. These numbers represent an upper limit because sedimentation is neglected.
Soot particles could also be lost by coagulation with larger sulfate aerosols and by condensation of H 2 SO 4 -H 2 O on the particle surface.
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