Figure 3-2: Size distribution of various aerosol types present in young
jet aircraft exhaust plumes (adapted from K�rcher, 1998a). Shown are approximate
size distributions (solid line) versus radius for volatile particles (neutral
and chemi-ion modes) and soot (primary and secondary modes), when no contrail
is produced by the aircraft. If a contrail is formed, these size distributions
change (not shown), and ice particles are created (dashed line). Size distributions
of soot and ice particles have been measured in situ. Mean sizes and numbers of
ion mode particles have been deduced from particle counter measurements, and corresponding
size distributions of volatile particles have been inferred from simulation models.
Bars indicate the approximate range of variability resulting from variations of
fuel sulfur content, engine emission parameters, and ambient conditions, as suggested
by evaluation of current observations and modeling studies. An approximate background
aerosol size distribution is included for comparison (dot-dashed line) (see Table
3-1).
