The meteorological trajectories for the various bursts cannot,
therefore, be computed at levels above 0,000 ft. and are doubtful
even at lower levels.
All trajectories given in this report were
computed by personnel of the Air Weather Service (SUPA Branch) and
are prepared for the 850-mb. (5,000-ft), 700-mb. (10,000-ft. ),
500-mb, (18,000-£t.), 300-mb. (30,000-ft.), and 200-mb. (h0,000-ft.),
levels only.
The temperature soundings for all of the Castle bursts were
very similar in their msjor features. There were no pronounced
inversions in the lower layers (except for an inversian at about
7,000 feet during Romeo). The air was quite moist up to about
5,000 feet, and somewhat drier above, with fairly steep lapse rates
in the upper troposphere.
The tropopause was between
48,000 and
5u,000 feet with very stable lavse rates in the lower stratosphere
above, The winds obtained from observations made at or near each
of the shots are shown in Figure 2.1.
2
.
2.1
BRAVO
_
yor
Le
The first burst of the Castle series, Bravo, was detonated from
@ coral reef in Bikini Atoll on 18L5 GCT, February 28, 195.
resulting cloud of radioactive debris reached to
this time was at about 54,000 feet,
feet,
The
The tropopause at
The low-level easterly trades
extended to about 6,000 feet, with light westerly winds increasing
throughout the stratosphere to the highest altitude reached by the
meteorological observations, about 100,000 feet. Winds at this level
were easterly at about 50 knots.
Trasectories of the lower parts of the cloud are shown in
Figure 2.2, but unfortunately, no trajectories can be constructed
for the higher levels.
Available evidence to about 100,000 feet
(observations in the Marshalls and at Guam) indicates general easterly
winds in the lower stratosphere, so that this portion of the cloud
moved toward the Phillipines. No observations to indicate the movement of the cloud above 100,000 feet are available. However, it is
likely that easterly winds prevailed at these levels.
The daily fallout maps for the period following the Bravo test
are particularly interesting in that tie background of fission
product activity from previous tests was negligible and the succeeding
burst did not occur until 26 days later, so that the progression of
areas of fallout from day to day is more easily seen,
-6-
rs,
soe
SECRET
ee
dale
with altitude to a maximum of aboyt hO knots at 350,000 feet,
extending to the base of the stratcsphere. lasterly winds prevailed