dimensions as a function of time. Corrections for cloud drift have been applied by using
wind measurements to plot the cloud trajectory.
The top of the cloud had not reached its maximum height by the time it had drifted be-
yond the instrumentation array 7 to 8 minutes after the detonation.
.
3.4 WINDS _DURING FALLOUT DEPOSITION
Shot Fig occurred at 1600 hours, after several hours’ delay caused by unfavorable wind
directions.
Single~theodolite balloon trackings were made at H~20, H~10, and H+3 minutes. To
infer hodographs from the data, it was necessary to assume either a known rise rate for
the balloon or known windspeeds. Experience gained on earlier double-theodolite trackings
during the day indicated that it would be best to assume known windspeed. Hodographs for
these three balloon releases are shown in Figure 3.5. Relatively large errors are possible
in range and elevation for these three hodographs; however, bearings are accurate to +0.001
radian.
Also shown in Figure 3.5 is a hodograph taken from the double-theodolite balloon tracking which started at H+9 minutes. This must be taken as the best description of winds that
existed during fallout deposition. However, some idea of variability with time is indicated
by the composite of Figure 3.5.
Balloon rise rates varied on these balloon runs, but all have been adjusted or normalized
to a rise rate of 1,000 ft/min. All of the hodographs have been superimposed on ground
zero for Shot Fig to show their orientation with respect to the instrumentation array. Results show that wind directions were ideal for fallout sampling. Windspeeds measured at
H+9 minutes varied from 11 knots for the layer from. the surface to 250 feet altitude to 16
knots for the layer from the surface to 5,000 feet.
Balloon runs at H+3 and H+9 minutes were recorded on film in addition to being recorded
manually.
3.5 MEASURED FALLOUT
3.5.1 Land Areas. Dose rates for all land stations at the reference time of 1 hour after
detonation are shown in Figure 3.6. These values weretaken entirely from monitor readings made with Jordan survey meters. Survey meter readings were used in preference to
RAMS data for the land stations, since the RAMS land equipment was damaged by an electrical transient produced by the nuclear detonation. In most cases, dose-rate values were
determined by more than one reading (sometimes as many as seven) during the period from
H+35 minutes to H+50 hours. For a given location, all readings were adjusted to the
reference time of H+1 hour, assuming t™'? decay.
An average of these H+1 hour dose
rates was computed and is the value shown for each station in Figure 3.6. Correction factors have been applied in those cases where the monitor stations were located near or on
the shoreline. These factors were never greater than 1.5.
Table 3.1 was constructed to give some idea of the relevance of the t'-? decay assumption to actual observations in the field. For each station location where three or more readings were obtained, the number of readings is listed together with the time interval (measured after zero time) during which the readings were taken. The fourth column is the
minimum percentage error that can be assigned to each dose-rate measurement in order
for all measurements made during the interval to be consistent with the t7':? decay rate.
For about 60 percent of the stations, errors smaller than +30 percent in dose-rate meas-
urement could, by themselves, explain apparent deviations from t~'*? decay. The very
40