The eastward moving debris reached the Americas on March 7
and 8, indicating an average west wind of about 40 knots, in good
agreement with the few wind observations available in the upper
troposphere.
Although the progression ef debris to the west
appears to be in good agreement with the 5,000-foot trajectory,
indicating that the transport occurred in the trade wind layers,
it is entirely possible that stratospheric debris moving with the
Upper level easterlies contributed te this fallout also.
The most striking fact which emerges from a study of the
fallout in the period following the Bravo test is the tendency
for the debris to remain in the tropical latitudes. By far the
largest amounts of fallout occurred in the latitude band from
10°S to 20°N, with occasional excursions into the more temperate
latitudes of each hemisphere, particularly in the Americas, An
example of this can be seen in the southwestern United States in
the period beginning March 15.
At this time, a deeo low pressure
system extending through most of the troposphere was located just
off the west coast, with strong southwesterly winds over the
southwestern states. This derression moved slowly eastward so that
by March 18th, the sout>westarly winds were over the “tississicpi
Valley. An examination of the fallout maps reveals that fallout
during this period was associated with the southwesterly winds,
which carried debris from the tropical regions. It is significant
that this fallout was independent of srecinitation. The highest
fallout values occurred during the first three days of the period
when there wag no precipitation, and evan on the 18th, when there
were several stations revorting precipitation, the fallout occurred
‘in the region dominated by the southwesterly winds and was not
closely associated with the existence of vreciritation.,
A somewhat
similar series of events occurred in the veriod March 21-25, although
precipitation was more widespread§n this case and may have had
more influence on the observed fallout patterns.
eek
'
Ae
The second burst of the Castle series, 2ona0,
from abarge at 1830 GCT, March 26, 196)
wag detonated
The wind observations associated witn this ourst ~
showed light easterly winds at virtually all levels increasing in
speed above 80,000 feet to a maximim of 92 knots from the SE at the
top of the highest observation, 95,000 feet. Although the trajectorie
(Figure. 2.3) at all levels in the tropospmere moved westward
initially, the 30,000- and 0,000-foot trajectories curved northward