vel. 98, No. 10 748 MONTHLY WEATHER REVIEW
suspicion that contrails may be influencing the weather
and that it is important to find out if they are.
In conclusion, it should be stated that if contrails are
affecting the weather it is not necessarily for the worse,
although if there is any considerable change it is sure to
make someone unhappy. The Russians might well be
pleased with an ice-free Arctic Ocean; but if it leads to a
major glaciation in central Canada, it is unlikely that the
Canadians and Americans would regard it as favorable.
ACKNOWLEDGMENTS
The writer wishes to acknowledge many discussions with Dr.
Sue Ann Bowling whose contributions have been so significant as
to nearly merit listing as a coauthor. The work upon which key
points in this presentation are based was supported by Grants
APOO 449-01, APOO 440-02, and APO 00449-03 from the National
Center of Air Pollution Control, Public Health Service, Department
of Health, Education, and Welfare. This work was partially sup-
ported by Grant GA-19475, Atmospheric Sciences Section, Na-
tional Science Foundation.
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Appleman, Herbert S., The Formation of Exhaust Condensation
Trails by Jet Aircraft, Bulletin of the American Meteorological
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Blanchard, D. C., A Verification of the Baily-Dorsey Theory of
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Braham, Roscoe R., Jr., and Spyers-Duran, Paul A., Survival of
Cirrus Crystals in Clear Air, Journal of Applied Meteorology,
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Fletcher, J. O., The Heat Budget of the Arctic Basin and Its Rela-
tion to Climate, Report R-444-PR, The Rand Corporation,
Santa Monica, Calif., Oct. 1965, 179 pp.
Fletcher, J. O., Managing Climatic Resources, Paper P-4000-1,
The Rand Corporation, Santa Monica, Calif., Mar. 9969, 27 pp.
Huffman, Paul J., Size Distribution of Ice Fog Particles, M.S.
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Livingston, W. C., Aircraft and Cloud Formation, Weather,
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Schaefer, Vincent J., The Inadvertent Modification of the Atmos-
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[Received December 22,1963; revised March 23,1970]
CORRESPONDENCE
UD C 551.501.81: 5.51.508.85: 621.396.969.181.3
Effect of Range on Apparent Height and Frequency of
High- AI ti tude Radar Precipitation Echoes
A. I. KANTOR and Q. D. GRANTHAM
Air Force Cambridge Research Laboratories, Bedford, Mass.
As coauthors of the captioned Monthly Weather Review
article (Vol. 97, No. 6, June 1969, pp. 429-431), we
welcome this opportunity to restate some of our findings
so that possible misinterpretation by interested readers
may be avoided.
Our conclusion concerning echo altitude and frequency
of occurrence due to range effects should state that the
net or resulting errors due to range are insignificant
rather than the errors are insignificant. The individual
errors can be substantial, as mentioned in our paper, and
as pointed out in a private communication from Dr.
D. Atlas, Director of the Laboratory for Atmospheric
Probing at the University of Chicago. We agree, for
example, that there is a balancing effect between the
increasing width of the beam with range that tends t o
increase the altitude of reported tops and the beam-width
averaging or filling effect that decreases the average
reflectivity of the top region with range. Also, height
errors obviously depend on reflectivity and its height
profile, so that, as Dr. Atlas emphasizes, serious over-
estimates of precipitation echo tops may occur when the
edges or side lobes of the beam detect sufficient reflectivity
from below. That such false echoes may occasionally
enter the records despite operational procedures and
professional manpower as used in the WSR-57 network
underscores the fact that reflectivity is a vital factor in
radar climatology of storm tops.