Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
associated with the model description of vertical and horizontal transport in the upper troposphere/ lower stratosphere.
The effect of current aircraft particle and particle precursor emissions (i.e., soot, sulfur, and water) in the stratosphere on ozone is estimated to be smaller than, and of
opposite sign to, the NO x effect. Model representations of aerosol microphysics and chemistry are, however, largely incomplete.
Aircraft-related increases in NO x in the upper troposphere are calculated to increase the concentration of hydroxyl (OH) radicals by a few percent throughout the
Northern Hemisphere. The OH change results in a corresponding decrease in the concentration of methane (CH 4 ). Uncertainties in the global budget of CH 4 and the
factors that control OH preclude testing this calculation with atmospheric observations. Because the chemical processes that lead to the reduction of CH 4 are the same
processes that increase ozone, calculated CH 4 and ozone effects are correlated.
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