A comparison of surface and airborne trace gas measurements at a rural Pennsylvania site

The aircraft and surface measurements of the trace gas concentrations were in better agreement when the aircraft measurements demonstrated uniform concentrations over the length of the flight path. The mean O₃ and H₂O₂ values of the lowest-altitude aircraft readings were usually greater than those measured at the surface, thus indicating higher-altitude sources and removal processes at lower altitudes. The aircraft-measured values for SO₂, NO_y, and hydrocarbons were usually lower than those measured at the surface, as expected for primary pollutants emitted near ground level. Closer agreement was obtained in the comparisons of secondary (O₃, H₂O₂) than of primary (SO₂, NO_y, hydrocarbons) pollutants. -from Authors