Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
Aviation and the Global Atmosphere
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2.3. Uncertainties in the Impact Assessment of Present Aviation: Implications for Use of Models in Predicting Future Change
2.3.1. Uncertainties in Modeling Aviation Impacts
2.3.1.1. Key Issues and Processes for Tropospheric Models
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In performing assessments of the impacts of subsonic aircraft NOx emissions on tropospheric composition, the modeling studies have pointed out several key issues
and processes that have to be adequately addressed:
Model spatial and time resolution
Time resolution of meteorological data
Subgrid-scale processes (e.g., plume processes)
Tropospheric NO x and NOy sources
Tropospheric gas-phase and heterogeneous chemistry
Stratospheric gas-phase and heterogeneous chemistry
Stratosphere-troposphere exchange
Upper troposphere-lower stratosphere dynamics and convective transport
Sources and sinks of water and NOy.
These issues and processes are discussed in general terms in the paragraphs that follow. A detailed description of process representation in the assessment models
is given in Chapter 4.
Over the years, there has been a steady increase in the spatial resolution of the models used in the assessment of subsonic aircraft impacts on tropospheric
composition. Initially, the assessment models were one-dimensional (altitude), averaged around latitude circles and from north to south poles. Relatively quickly,
researchers realized that interhemispheric gradients were crucial for ozone and anthropogenic trace gases, so much of the assessment work has been carried out with
2-D (altitude and latitude) models that average around latitude circles. With NO x lifetimes of days or less and transport times around latitude circles of up to 2 weeks,
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