Realistic Mixing Depths for Above Ground Aircraft Emissions

Analysis of vertical temperature soundings at Los Angeles International Airport (LAX) shows that a conservative height of the inversion base for pollutant containment purposes is 490 ft (150 m). This altitude is considerably less than the 3000 ft (914 m) pollution containment altitude assumed by the EPA in preparing their emission inventory for the airport. (Figure 1.) After correcting the EPA emission inventory to reflect a real world inversion height, the emission inventory for aircraft at Los Angeles International Airport is estimated to be approximately 50% less. Aircraft thus become a less significant pollution source and consideration should be given to relaxing engine emission control requirements accordingly.

This paper examines current emission control philosophy, which according to the EPA should be based upon the significance of the particular polluting source. The problem of accounting for above ground aircraft emissions is then considered. Daily inversion height data are then used to determine a realistic vertical containment altitude for aircraft emissions. Problems in obtaining good inversion data are described. Finally, aircraft emissions at Los Angeles International Airport are adjusted to reflect real world inversion conditions on those days when the inversion height is low enough to influence significantly air pollution levels. Recommendations are made for additional research leading to possible change to NO_x emission control requirements for aircraft.