Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
in this context refers to an atmosphere derived from a calculation that includes all expected
inputs other than those attributable to aircraft emissions. The calculated impacts of aviation
on ozone for 1992, 2015, and 2050 are provided by Chapter 4. The small effect calculated
for 1970 is deduced from the 1992 calculations, as discussed in Section 5.4.1.2.
The starting point for subsequent calculations is the representation of ozone columns and
profiles for 1992. For this chapter, the columns have been derived from archived TOMS
version 7 measurements (Herman et al., 1996). UV calculations have been performed at
local noon for January, April, July, and October at the following latitudes: 65°S, 45°S, 30°S,
0, 30°N, 45°N, and 65°N. The monthly averaged and zonally averaged ozone columns
derived from the TOMS data for these months and latitudes for the 10-year period 1983 to
1992 are shown in Table 5-1.
Because the values shown in Table 5-1 are averages of measured values, they already
include the effects of present-day aircraft emissions on ozone. In other words, to obtain the
1992 background atmosphere, the effects of emissions from aircraft have to be removed
from the values shown in Table 5-1. The manner in which this has been done for these
calculations and the extension of the methods applied to obtain the required information for
the years 1970, 2015, and 2050 are illustrated in Figure 5-3.
Figure 5-3: Illustration of the derivation of columns used for UV
All calculations ultimately have averaged values for ozone given in Table 5-1 as their
calculations.
reference. These 1992 values are represented by 1992ss (where the subscript defines an
atmosphere containing emissions from a fleet of subsonic aircraft) in Figure 5-3. Chemical transport calculations are carried out to generate model atmospheres for
1992 that (a) do not include inputs attributable to aviation and (b) do include these inputs. Comparison of the results of these calculations allows one to determine the
absolute differences in ozone concentrations predicted by the model.
Table 5-2: Brief scenario description.
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