In situ measurements of HOx in aircraft exhaust plumes and contrails during SUCCESS

In situ flight measurements of the hydroxyl (OH) and hydroperoxyl (HO2) radicals were performed in the exhaust plume of a Boeing 757 and in the contrail. of a Douglas DC-8 flying under typical cruise conditions in the upper troposphere and lower stratosphere during the SUCCESS mission of April and May 1996. Measurements were made in a range of exhaust plume ages from roughly 10 seconds to 20 minutes. OH mixing ratios were found to be greatly enhanced in the plumes, to 2-5 pptv from a background of 0.3-0.5 pptv in young plumes, and to 0.6 pptv from a background of less than or equal to 0.2pptv in older contrails. HO2 mixing ratios were heavily suppressed in the plumes, to 2-4 pptv from a background of 10-20 pptv, for both young plumes and older contrails.