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The horizontal motion of the falling particles results prinarily
from the action, winds which are observed by conventional wind
messuring equipment.
The procedures for utilizing winds for tha
cotermination of fallout areas are entirely straight-forward, ‘the
falling particle is transported horizontally by the wind in a layer
depending upon its stay in the layer before settling to the next
lower level. The summation of the horizontal displacezents ends
with the ground deposition of the particle.
In addition to transport by the usuzlly=observed winds, there
is @ certain amount of lateral dispersion because of horizontal
turbulence in ths atmosphere, Experience suggests that in most
cases, the spread of falling particles by the winds so0 grestly
exceed the spread due to small-scale turbulence that the latter |
effect 1s usually ignored.
.
:
from the ground
In theprediction of radiationganaintensities/ it is
necessary to know not only the winds and physical characteristics
of the falling particles, but also the emomt of radioactivity
as a function of particle sizefffftuds, this latter infornation
is essentially gf non-meteorological problem and will not be dealt
with at this tims,
An example of the final result of ths
application of metscrological winds to a model of radioactivity
as a fimction of altitude and particle size is shown in the first
few figures.
Toe first figure shows the actual and predicted isolinss of
gamzs activity in rilliroontzens per hour referred to tielve hours,
The light dashes, the observed field, were derived from ground
monitoring along various roads eround the Nevada Test Site.
Ths
heavy lines show the predicted fallout pattern using a Veather
Burean model of cloud radioactivity.
this picture, tha winds
measured near the explosion place and tins, which ware rainly from
south to north, were assumed to carry particles at all later tires
and places,
It is evident that the prediction, the type made most
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