and then eastward within a very short time. The lowest levels continued westward and the 18,000-foot trajectory appeared to curve

back towards the United States on the 28th, although the meteoro-

logical data is uncertain. Winds in the stratosphere up to the
level of the ton of the cloud were probably from the east, carrying

most of the mushroom westward,

Although almost a month elapsed between the first and second
bursts of the Castle series, enoughdebris from the first burst was

present to seriously interfere with attempts to trace the progress
of the. second clow by an examination of fallout data. For example,
an increase in deposited activity occurred at some stations in

Central and South America on March 31 and April 1, several days

before the meteorological trajectories would indicate the arrival

of debris. It is not certain if this is due to the complete lack
of meteorological observations in the Eastern Pacific and the winds
were really stronger than assumed, or that the debris was actually
from the Bravo burst.
(Note: Since all fallout data is extrapolated
to 100 days after the assigned burst, values assigned to different
bursts cannot be compared directly. The extracclation factor denends
both on the day of the burst and on the day the sample was counted.
For the areas mentioned in this saragrarh, values assigned to burst
2 would have to be increased by about a factor of three if the debris

were assignedtabursti).

By April 2nd and 3rd increases in activity are evident along the

' Gulf Coast of the United States and certainly by the lth and 5th there
is good evidence that debris from this burst has arrived over the
United States. Again, as when fresh Bravo debris was present,fallout
seemedto occur irrespective ofithe occurrence of precipitation.

The progression of debris westward from the. test. site appears to.
have been more rapid than indicated by the low-level trajectories

at 5,000 and 10,000 feet, at least for the first few days following
the burst. Whether the arrival of debris at Yap and Koror on March 29

is a result of transnort of material westward in the stratoscheric
easterlies or in faster-than-observed low-level trades is not certain.
Again, as with Bravo debris, there was 2 marked tendency for the
fallout to occur in the tropical areas, with occasional incursions into
the United States.

2.3 KOON
Koon, the third burst of the series

;

.
was detonated at
Bikini 31820 GCT, Avril 6, 19S). but cloudy conditions prevented

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SS

Select target paragraph3