Quantification of the Impact of Very Short Lived Chlorine Compounds on Stratospheric Chlorine

Very short lived (VSL) halogens contribute a significant amount to the stratospheric burden of total reactive bromine as well as increasing amounts of reactive chlorine. VSL bromocarbons that reach the stratosphere primarily originate from natural oceanic processes and their influence seems to be constant over time, whereas VSL chlorocarbons that reach the stratosphere mainly result from various human activities (e.g., solvents, foam blowing agents, the production of polyvinyl chloride products, etc) and their influence appears to be rising over time. Nonetheless, VSL chlorocarbon compounds are not regulated by the Montreal Protocol. In this presentation we review the abundance of VSL chlorine reaching the stratosphere based on measurements of organic compounds in the tropical tropopause transition layer, and relate these observations of VSL chlorocarbons to satellite and ground-based observations of stratospheric inorganic chlorine in the mid-latitude, lower stratosphere as well as to observations from the surface-based flask and in-situ measurements. A major focus of this presentation is on defining the time rate of change of the stratospheric injection of VSL chlorine, a quantitative aspect of critical importance for our companion study of ozone trends in the mid-latitude, lower stratosphere.