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KRUGER, HOSLER, AND MILLER
within the cloud and that direct capture below the cloud is relatively
unimportant.°
Experiments
During the period from 1961 through 1963, a total of 14 convective
shower systems has been studied. In each case time aliquots of the
showers were obtained of the minimum sample size ‘consistent with
adequate sensitivity for radiochemical analysis. The use of radar
analysis of the cloud systems was increased each year. Maximum
radar-echo cloud tops were measured’ for the seven showers sampled
in 1961. Radar-echo cloud-top profiles were obtained’® for the three
1962 showers. Time—height—intensity (THI) cross sections were pre-
pared’® for the four 1963 showers, These cross sections, showing the
radar reflectivity structure with altitude in the clouds, have proved
invaluable in conjunction with general meteorological data in evaluating
the fallout concentrations, The methods of collection and radiochemical
analysis of the precipitation have been given in our earlier reports.!
Summary
The collection, radiochemical, and meteorological data fox eue indi-
vidual 14 convective showers studied to date are given in Refs. 3, 15,
and 16. A summary of these data ie given in Table 1. The peak Sp
concentration in each shower was compared to the average concentration for the shower as a whole. The maximum radar-echo tops are
given for each shower corrected to mean sea level. For the 1962 and
1963 showers, the time of the peak cell top from the radar cross section was compared to the time of the peak Sr concentration. The
distance of the shower’s position with respect to the jet-stream location
and the height of the tropopause was also determined for each event.
As illustrations of the data previously reported, one of the radartop cross-section analyses of the 1962 convective showers is shown in
Fig. 1, and one of the THI reflectivity-cross-section analyses of the
1963 showers is shown in Fig. 2. In all the 1962 and 1963 showers, the
average precipitation rate and the age of the strontium fission products
(given by the 88Sr/sSr ratio) were also calculated. These data are
shown in the respective cross-section analyses,
Discussion
The convective-activity showers studied in the period from 1961
through 1963 involved nuclear-weapon debris of differing time origin
each season. The 1961 showers contained “Sr debris at least three
years old, originating from nuclear-weapon tests prior to the mora-
torium of 1958. The average "Sr concentration was low, usually less
than 1 dis/min per liter. The debris in these storms came from well-