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Science 15 June 1984:
Vol. 224. no. 4654, pp. 1210 - 1214
DOI: 10.1126/science.224.4654.1210
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Articles

Diurnal Variation of Stratospheric Chlorine Monoxide: A Critical Test of Chlorine Chemistry in the Ozone Layer

P. M. Solomon 1, R. de Zafra 2, A. Parrish 3, and J. W. Barrett 3

1 Professor of astronomy, State University of New York, Stony Brook 11794.
2 Professor of physics at the State University of New York, Stony Brook 11794.
3 Research associate, State University of New York, Stony Brook 11794.

This article reports measurements of the column density of stratospheric chlorine monoxide and presents a complete diurnal record of its variation (with 2-hour resolution) obtained from ground-based observations of a millimeter-wave spectral line at 278 gigahertz. Observations were carried out during October and December 1982 from Mauna Kea, Hawaii. The results reported here indicate that the mixing ratio and column density of chlorine monoxide above 30 kilometers during the daytime are sim 20 percent lower than model predictions based on 2.1 parts per billion of total stratospheric chlorine. The observed day-to-night variation of chlorine monoxide is, however, in good agreement with recent model predictions, confirms the existence of a nighttime reservoir for chlorine, and verifies the predicted general rate of its storage and retrieval. From this evidence, it appears that the chlorine chemistry above 30 kilometers is close to being understood in current stratospheric models. Models based on this chemistry and measured reaction rates predict a reduction in the total stratospheric ozone content in the range of 3 to 5 percent in the final steady state for an otherwise unperturbed atmosphere, although the percentage decrease in the upper stratosphere is much higher.

Submitted on August 29, 1983
Accepted on March 12, 1984

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Science. ISSN 0036-8075 (print), 1095-9203 (online)