The meteorological trajectories for the various bursts cannot, therefore, be computed at levels above 40,000 ft. and are doubtful even at lower levels, All trajectories given in this report were computed by personnel of ths Air Weather Service (SUPA Branch) and are prepared for the 850=mb. (5,000-ft), 700=-mb. (10,000-ft.), 500=-mb. (18,000-ft.), 300-mb. (30,000-ft.), and 200-mb, (0,000-ft. ), levels only. The temperature soundings for all of the Castle bursts were very similar in their mjor features. There were no pronounced inversions in the lower layers (except for an inversion 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 wes between 18,000 and 5,000 feet with very stable lapse 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. 2.1 BRAVO The first burst of the Castle series, Bravo, wes detonated from a coral reef in Bikini Atoll on 1845 GCT, February 26, 195. The resulting cloud of radioactive debris reached to 114,000 feet with the base of the mushroom at about 60,000 feet. The tropopause at this time was at about 54,000 feet, so that the mushroom of the cloud wes entirely in the stratosphere. The low-level easterly trades extended to about 6,000 feet, with light westerly winds increasing with altitude to a maximum of about 0 knots at 35-1:0,000 feet, extending to the base of the stratosphere. Easterly winds prevailed throughout the stratosphere to the highest altitude reached by the meteorological observations, about 100,000 feet. were easterly at about 50 knots. Winds st this level Trajectories of the lower parts of the cloud are show in Figure 2.2, but umfortunately, 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 movw- ment 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 the background of fission product activity from previous tests wes negligible and the succeeding burst did not occur until 26 dsys later, so that the progression of areas of fallout from day to day ts more easily seen. =~ 6 =