Vertical profiles of tropospheric gases: Chemical consequences of stratospheric intrusions

The M.R.F. Hercules aircraft was used to obtain two vertical profiles of minor atmospheric constituents in a stationary low pressure circulation over the N. Atlantic. Results for CFCl 3, CF 2Cl 2, N 2O, C 2H 2, C 2H 6, C 3H 8, C 4H 10 and O 3 are presented, and interpreted by means of air parcel back trajectories on isentropic surfaces. Substantial evidence was found for air of stratospheric origin in the upper troposphere on the second flight, and the data from both flights point to an enhancement in OH concentrations, and thus hydrocarbon depletion rates, following mixing between stratospheric and tropospheric air.