496 Discussions

REFERENCES

DAVIES C. N. (1965) The rate of deposition of aerosol particles from turbulent flow through ducts. Ann. occup. Hyg. 8,239-245.

DAMES C. N. (1966a) Deposition of aerosol from turbulent flow through pipes. Proc. R. Sot. A, 289, 235-246.

DAV~E.S C. N. (1966b) Deposition from moving aerosols, in Aerosol Science, Academic Press, London. KNEEN T. and STRAUSS W. (1969) Deposition of dust from turbulent gas streams. Atmospheric

Environment 3, 55-67. SEHMEL G. A. (1968) Aerosol deposition from turbulent airstreams in vertical conduits. Report

BNWL 578, Battelle Memorial Institute, Richland, Wash. USA. WELW A. C. and CHAMBERLAIN A. C. (1967) Transport of small particles to vertical surfaces. Br. J.

appl. Phys. 18, 1793-1799.

Health Physics and Medical Division, Building 364, A.E.R.E. Harwell.

A. C. CHAMBERLAIE~

Atmospheric Environment Pergamon Press 1969. Vol. 3, p. 496. Printed in Great Britain.

LIDAR MEASUREMENT OF BACKSCATTER AND ATTENUATION OF

ATMOSPHERIC AEROSOLS*

I WOULD lie to say that I am pleased with this paper,* because it describes one means by which a highly important relationship can be obtained -tally rather than by making assumptions, as I did in my paper (cited by Dr. Hamilton). I am equally pleased to note that the data he obtained on 31 May 1968 yielded a ratio of extinction to backscatter coefEeients which is in good agreement with the ratio (2.05) which I arrived at by means of the Mie theory and a set of assumed aerosol properties and which I have used in all my subsequent work.

The only drawback to Dr. Hamilton’s technique is that, on many occasions, the aarc@ distribution is highly inhomogeneous in the horizontal. On such occasions, the data points will, of course, show great scatter when plotted against the cosecant of the elevation angle, so that it will be obvious that the method will not work at that time. However, there will be enough times when the horizontal homo- geneity will be adequate to permit acquisition of a body of statistics on tbe relationship between back- scatter and extinction.

Atmospheric Physics and Chemistry L.aboratory U.S. Department of Commerce Environmental Science Services Aabdnistration Research Laboratories Boulder, Colorado 80302, U.S.A.

EARL W. B~aanrr

* Atmospheric Environment (1969). 3 (2), 221-223.