An analysis of aircraft exhaust plumes from accidental encounters

An analysis of data obtained during the second Airborne Arctic Stratospheric Expedition (AASE‐II) was made with emphasis on aircraft exhaust plumes accidentally encountered during the mission. Twenty spikes were found with peak NO y increments ≥1 ppbv. The examination of CO and CO 2 indicates that there was only one NO y spike having clearly corresponding spikes of both CO and CO 2 , and another four with unambiguous CO 2 spikes. No significant increases were found for CH 4 and N 2 O for these 5 spikes. The ratio of the excess CO 2 and NO y compares well with the ratio of published subsonic aircraft emission indices. The study of the selected spikes from the DC‐8 and another two spikes observed during other missions shows that the odd nitrogen other than NO x accounts for a very small percentage of the NO y increase associated with the observed spikes.