METEOROLOGICAL INFLUENCES ON “sr CONCENTRATIONS
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in the precipitation from such storms may be expected to be dependent
upon the slower changing meteorological features of large-scale uplift.
The effects of frontal zones and changes in generating mechanisms
shouldbe observable as perturbations on the steady state of the large- .
scale uplifting. For precipitation from large air masses, the groundlevel concentration of nuclear debris was believed’ tobe dependent upon
the following parameters:
1. The height of the precipitation-generating level.
2. The precipitation generation and growth mechanisms in the cloud.
3. The amount and the characteristics of the radioactive aerosols
initially in the air masses participating in the precipitation process.
4. The specific humidity at the generating level.
5. The previous precipitation experience of the air at the generat-
ing level.
6. The descent experience of the precipitation from the cloud in
which the precipitation originates to the ground,
Summary of Part 1 (Reported in Ref. 1)
Our initial studies of three wave cyclones in the winter of 1960 at
Pittsburgh, Pa., were concentrated upon storms in which thestability
of the air led to layer clouds with limited imbedded convective activity.
In each storm, the precipitation elements were generated in the ice phase
at approximately 18,000 ft. Thus the first two variables given above
were considered constant. By an additional limitation of observations
to precipitation involving only one air mass with an expected conserva-
tion of debris to water ratio, the second two variables were con-
Sidered constant for the period of precipitation. Even with these ap-
proximations, the changes of "Sr concentration in the rain were
observed to be strongly dependent upon descent experience as expressed in terms of ceiling height. The ceiling may be considered an
index of the humidity profile and the depth of the lower layers of air.
These parameters affect the rate of evaporation or the growth of the
raindrops falling from the cloud and thus the final ground-level
concentration.
Newer Experiments
Subsequent continental cyclonic storms were sampled at State
College, Pa,, at the site of the Pennsylvania State University 3-cm
M33 radar system, with which data time cross sections of the clouds
and precipitation were prepared. Ceiling balloons were released to
measure ceiling heights. Since 1962 a detailed radiochemical study of
a complex Pacific Ocean wave cyclone has been made”? in addition to
an analysis of the nuclear-debris deposition in California from wave
cyclones during the winter 1961-1962 following resumption of nuclear