The atmospheric column abundance of IO: Implications for stratospheric ozone

Creators: Wennberg, P. O.; Brault, J. W.; Hanisco, T. F.; Salawitch, R. J.; Mount, George H.

Abstract

Absorption attributable to atmospheric IO is observed in high-resolution, high air mass solar spectra taken at the National Solar Observatory, Kitt Peak, Arizona, in March 1995. These observations, together with cross sections measured in the laboratory for the IO {A^(2)Π3/2←X^(2)Π_(3/2) (2,0)} rotationally resolved electronic transition, are consistent with a total stratospheric iodine mixing ratio of 0.2 (+0.3 −0.2) parts per trillion by volume. This result, combined with recent laboratory measurements of the rate of the reactions of IO with other halogen species, suggests that iodine chemistry is not responsible for the reductions observed in lower stratospheric ozone during the last several decades.

Additional Information

© 1997 American Geophysical Union. Received January 3, 1996; revised November 17, 1996; accepted November 18, 1996. Paper number 96JD03712. We would like to thank the many individuals and programs that contributed to this work. At Harvard, support for the purchase of the Bruker FTS was provided through grants from the National Science Foundation (ATM-8921312) and the Empire State Electric Energy Research Corporation. Support for P.O.W. and T.F.H. was provided by the National Aeronautical and Space Administration (NASA) Upper Atmosphere Research Program (NAG-1-1305). At Kitt Peak we would like to thank the National Solar Observatory for use of the McMath-Pierce telescope and the solar spectrometer. Research by R.J.S. at the Jet Propulsion Laboratory, California Institute of Technology, was performed under contract with NASA. Paul Newman from NASA Goddard kindly provided information on the tropopauseh eight above Kitt Peak. We thank M.J. Kurylo, A. R. Ravishankara, and J .-P. Pommereau for sharing information from their laboratories on the kinetics and photochemistry of iodine prior to publication. Finally, we would also like to thank Kathy Perkins, Kelly Chance, Stan Sander, and Susan Solomon for their comments on the manuscript.

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