Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
The results of the sensitivity studies are presented in Table 4-6. The table presents the relative sensitivity r (%) of each process by comparing aircraft-induced
increases in global O 3 for the base case and the sensitivity case:
r = [(O 3 ,2-O 3 ,1)/O 3 ,1]*100% (1)
where O 3 ,1 is the global O 3 increase (kg) up to 16 km for the base case in 2015 (i.e., scenario
D-C) and O 3 ,2 is the same increase calculated for the sensitivity study (i.e., scenario D'-C'). The
sensitivity studies show that increases in background NO x from lightning (sensitivity study 1)
and different growth rates in surface emissions in different regions (sensitivity study 2) have
only a slight impact on O 3 perturbation from aircraft emissions. In both cases, O 3 perturbations
are reduced. This finding shows that O 3 production in the UT and LS is limited by NO x , rather
than by hydrocarbons. Interannual variability in meteorology (sensitivity study 6) and exclusion
of heterogeneous removal of N 2 O 5 in the models also led to a small change in global average
O 3 perturbation (sensitivity study 5). Excluding hydrocarbon chemistry (sensitivity study 4)
would have a significant impact on O 3 , resulting in a smaller perturbation. Furthermore, there
were significant differences in the results between the two models used to perform the study.
Comparison of results with two different emission scenarios (sensitivity study 3) showed a
noticeable impact on global O 3 perturbation. Sensitivity study 7, which was set up to test the
response of O 3 perturbation to greatly increased NO x emission from aircraft (estimated upper
limit in 2050), showed that the response is nearly linear and similar to what is computed for
smaller NO x perturbations.
2
The model results presented in this chapter are a summary
of muchmodel output. Supplemental material regarding the
effects of supersonic aircraft are retrievable over the
Internet. Supersonic model simulation information includes
figures, tables, and text and is available at a NASA Langley
Research Center computer until 31 December 2000:
Host: uadp1.larc.nasa.gov
Username: anonymous
Password: your e-mail address
Directory: IPCC_TECH_REPORTS/supersonic
Information concerning supersonic model simulations may
also be viewed (retrieved) over the Web by going to the
following URL: ftp://uadp1.larc.nasa.gov/
IPCC_TECH_REPORTS/supersonic/.
It should be noted that the comparisons in Table 4-6 are made for global average O 3 perturbations; sensitivities are larger on regional and seasonal scales.
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