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Large Decrease in the Clear Air Transmission of the Atmosphere 1.7 km above Los Angeles


ASTRONOMICAL measures of atmospheric extinction, routinely carried out during most programmes of astronomical photoelectric photometry, provide a large sample of data of importance to studies of long term anthropogenic pollution of the atmosphere1. We have therefore begun an exhaustive compilation of present and past measures of extinction at as many observatories throughout the world as possible. I wish to point out one of the most important results so far, the measurement of a large secular decrease in the transmission of the atmosphere measured at a significant altitude above the Los Angeles Basin.

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    Charlson, R. J., Hodge, P. W., Lucke, P. B., Mannery, E. J., Porch, W. M., and Snow, T. P., University of Washington Project ASTRA, Publication No. 2 (1970).

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    Hardie, R. H., in Astronomical Techniques, 178 (edit. by Hiltner, W. A.) (Chicago University Press, 1962).

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    Porch, W. M., Charlson, R. J., and Radke, L. F., Science (in the press).

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    McCormick, R. A., and Ludwig, J. H., Science, 156, 1358 (1967).

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