594
KRUGER, HOSLER, AND MILLER
testing by the U.S.S.R.”*> From these studies, some of the parameters
significant in determining nuclear-debris-deposition mechanisms by
cyclone
precipitation
have
been
examined.
The collection,
radio-
chemical, and meteorological methods for these studies have been
the same as those reported in Ref. 1.
Concurrent studies under another program are being made by
aliquoted collections along the entire length of the 1500-mile west coast
of the United States, Examination is being made of the meteorological
parameters on the synoptic scale encompassing an entire wave cyclone,
including the effects of wave history, air-mass trajectories, storm
intensities, variation in the height of the tropopause, location and in-
tensity of the jet stream, etc. One such cyclone’! was sampled in
March 1962.
Discussion
The data for the several wave-cyclone studies are given in Refs.
2 and 22. These data are summarized, with pertinent illustrations
given, in the discussion of the parameters observed to be important in
determining ground-level Sr deposition rate from the wave cyclones
examined.
Evaporation This effect has been discussed.’ It has already been
pointed out by Bleichrodt ef al.” that evaporation of raindrops falling
through unsaturated layers of air should lead to increased concentration of radioactivity in rainfall. This effect should be especially
pronounced for steady precipitation of relatively small drops that often
accompany large-scale disturbance. For example, data taken from
Mason’ indicate that evaporation would reduce the volume of a drizzle-
size drop falling from a cloud base 2000 ft above ground through air
of 80% relative humidity by a factor of 16. The onset of rain from large
cyclonic storms is frequently from middle clouds; thus the effect of
evaporation on ground-level nuclear-debris concentration should be
especially strong during the first few hours of rain,
Studies of the cyclones in central Pennsylvania were made to
isolate the collection periods during which precipitation fell from
stable single air-mass systems with no observable change in cloud
tops or storm structure. Analyses of changes in Sr concentration
were made in terms of changes in ceiling height. Figure 5 shows the
fractional change in *Sr concentration, AC, as a function of the fractional change in ceiling, AH. A line drawn throughthe origin indicates a
relation expressed by
In C = In 1-250. 65
When the assumptions of steady-state precipitation conditions, the
variability in temperature and humidity profiles below the clouds,