RADIOACTIVITY IN PRECIPITATION
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noon, with small weak cells moving through the network. A line of
storms developed about 30 miles east of Norman and moved eastward,
Around 1545 CST convective activity west of the network increased. By 1600 CST a definite line was taking shape, and at 1700
CST it was about 20 nautical miles across, oriented southwest—
northeast with range limits at 250 degrees azimuth and 100 nautical
miles range and 300 degrees azimuth and 40 nautical miles range,
respectively. The line was moving eastward at about 30 knots with the
southern end passing through the network.
The time sequence of echo intensities for the storm is given in
Fig.
29.
It
can be seen as the eastern-moving storm entered the
network there were two large major cells that were developing. The
northernmost cell moved out of the network before dissipating, but the
southernmost cell was already decreasing in intensity before leaving
the network. There was minor cell development behind the squall line.
During the period 1801-1807 CST, the radar top of the northern
cell was at 46,000 ft. Table 2 shows the tropopause at 43,296 ft; thus
this
cell had penetrated into the stratosphere, The southern cell had
radar tops of 44,000 ft and was intensifying as it approachedstation 8.
The time cross sections of radar tops over the stations (Figs. 30 to 33)
show storm tops near tropopause height over collectors 1, 4, 8, and 9.
Figs. 34 to 37 are the rainfall-sample cross sections for the 10 col-
lectors, all of which obtained multiple samples. The beta-concentration
profiles for all the collectors except those at station 1 show a decrease
in total beta concentration from the initial to the second sample with a
corresponding increase in rainfall rate, At station 1 the rainfall rate is
2.16 in. per hour for the first two samples with the total beta concentration increasing from the first sample to the second.
The beta concentration was at a maximum in the initial sample at
four stations (2, 3, 4, and 9) and at a maximum in the final sample at
four stations (5, 6, 7, and 8), Of these eight stations, 3, 4, 5, 7, and 9
have their minimum beta concentrations associated with their maximum rainfall rates. The rainfall-rate maximumsat six of the stations
(1, 2, 3, 5, 6, and 8) correspond to maximums in ratios of particulate
to dissolved beta activity. Generally, the ratios of the initial samples
were low; these low values possibly were due to little dust blowing as a
result of the previous day’s rains.
The time sequence of radar-intensity centers (see Fig. 29) shows
that one of the centers crossed the upper two-thirds of the network
whereas the other crossed the most southern row of stations, The
collection at station 1 was multicellular with the rainfall-rate maxi-~
mum being from the cell (see Fig. 29) whose center passed north of
the collection network. The collections at this station from the cell
that crossed the network show that the rainfall rate from that portion
of the cell was weak, with radar storm tops around 34,000 ft. The area
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