Chemistry Faculty Publications

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Journal of Geophysical Research: Atmospheres

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The amount of chlorine in the stratosphere has a direct influence on the magnitude of chlorine-catalyzed ozone loss. A comprehensive suite of organic source gases of chlorine in the stratosphere was measured during the NASA Stratospheric Aerosol and Gas Experiment (SAGE) III Ozone Loss and Validation Experiment (SOLVE) campaign in the arctic winter of 2000. Measurements included chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halon 1211, solvents, methyl chloride, N2O, and CH4. Inorganic chlorine contributions from each compound were calculated using the organic chlorine measurements, mean age of air, tropospheric trends, and a method to account for mixing in the stratosphere. Total organic chlorine measured at tropospheric levels of N2O was on the order of 3500 ppt. Total calculated inorganic chlorine at a N2O mixing ratio of 50 ppb (corresponding to a mean age of 5.5 years) was on the order of 3400 ppt. CFCs were the largest contributors to total organic chlorine (55-70%) over the measured N2O range (50-315 ppb), followed by CH3Cl (15%), solvents (5-20%), and HCFCs (5-25%). CH3Cl contribution was consistently about 15% across the organic chlorine range. Contributions to total calculated inorganic chlorine at 50 ppb N2O were 58% from CFCs, 24% from solvents, 16% from CH3Cl, and 2% from HCFCs. Updates to fractional chlorine release values for each compound relative to CFC 11 were calculated from the SOLVE measurements. An average value of 0.58 was calculated for the fractional chlorine release of CFC 11 over the 3-4 year mean age range, which was lower than the previous value of 0.80. The fractional chlorine release values for HCFCs 141b and 142b relative to CFC 11 were significantly lower than previous calculations.


This article was originally published in Journal of Geophysical Research: Atmospheres.

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