Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
Aviation and the Global Atmosphere
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4.3. Model Studies of Supersonic Aircraft
Other reports in this collection
This section contains an evaluation of the effects of supersonic engine effluent on stratospheric O 3 , NOy, H 2 O, and other trace constituents. The assessment of the
potential future supersonic aircraft fleet was conducted primarily with 2-D and 3-D CTMs. These global models are designed to represent the dynamic, chemical, and
physical processes of the stratosphere. Chapter 2 discusses the validity of these models to accurately represent the present atmosphere.
Because these future aircraft have not yet been designed, we treat our study of supersonic aircraft in a parametric way. This assessment performed calculations for
more than 50 supersonic scenarios and examined variables such as EI(NO x ) and fleet size, ambient SAD and chlorine radical abundances, SO 2 gas-to-particle
conversion in the aircraft plume, cruise altitude sensitivity, and model cold aerosol chemistry representation. Results from this section are incorporated in Chapters 5
and 6.
4.3.1. Models Used in Supersonic Aircraft Assessment
This section presents calculated responses of O 3 to HSCT aircraft from nine numerical models of the stratosphere. These nine modeling groups have been responsible
for most recent publications on the subject. We restrict our analysis to this set of results because it is difficult to compare model results unless the models are produced
in the same way. For example, it is difficult to compare the results here with recent publications of Dameris et al. (1998) because they isolated the effect of NOx emission by excluding other emissions from their simulation.
The six 2-D models and three 3-D models are listed in Table 4-7. The 3-D models obtain 3-D distributions of the species by solving 3-D mass continuity and chemistry
equations. The 2-D models calculate the zonal-mean concentrations of the species by solving zonal-mean mass continuity equations. Transport of the zonal-mean
concentration is affected by zonal-mean (vertical and horizontal) winds and eddy diffusion fluxes that simulate the effects of zonally asymmetric motions. Chemical
packages are used to compute zonal-mean production and loss rates for each species. In this section, we highlight some of the differences in model formulations that
may have contributed to differences in model predictions. The reader is referred to the Technical Report on Supersonic Aircraft Effects for additional details.2
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