Nitrogen oxides from high-altitude aircraft: an update of potential effects on ozone

A sensitivity study is carried out using chemical-radiative-transport models of the global atmosphere to examine possible effects of future aircraft NO_x emissions to stratospheric ozone. The altitude at which NO_x emissions cause the largest reduction in the ozone column is about 25 km according to one-dimensional model calculations and about 28 km according to the two-dimensional mode. Maximum ozone reduction occurs for tropical injection. For a given injection, the largest ozone column reductions occur in the polar regions. For very large Cl_x mixing ratios, NO_x emissions can increase the ozone column, partially counteracting the ozone reduction caused by Cl_x. On the basis of an uncertain estimate of fuel consumption by future stratospheric aircraft, calculations for a fleet of 500 aircraft operating at 22 km with NO_x emission properties of 1988 subsonic commercial aircraft engines give global ozone reductions of about 20%. -from Authors