Estimate of late 1974 stratospheric concentration of gaseous chlorine compounds (ClX)

We estimate the total concentration [ClX] versus altitude of Cl‐containing molecules, principally HCl, Cl and ClO. The predicted present stratospheric concentrations appear to be due to photolysis near 30 km of man‐made CF 2 Cl 2 and CFCl 3 , and CCl 4 from a ground‐level source, man‐made or natural. Based on preliminary measurements of CH 3 Cl at ground we estimate its contribution to stratospheric ClX through the major known loss mechanism for CH 3 Cl, abstraction by OH. Ground‐level sources of HCl and Cl 2 are large but tropospheric processes preclude significant impact on the stratosphere. Our computed profiles are consistent with first HCl concentrations measured by Lazrus et al. [1974, 1975] in the 15–27 km region.