The eastward moving debris reached the Americas on March 7 and 8, indicating an average west wind of about 0 knots, in good agreement with the few wind observations available in the upper troposphere. Although the progression of debris to the west appears to be in good agreement with the 5,000-feoct trajectory, indicating that the transport occurred in the trade wind layers, it is entirely possible that stratospheric debris moving with the upper lewel easterlies contriluted to 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 remin in the tropical latitaies. By far the largest amounts of fallow occurred in the latitude bend from 10°S to 20°N, with occasional excursions into the more temperste latitudes of esch 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 deep 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 depression moved slowly eastward so that by Maveh 18th, the southwesterly winds were over the Mississippi Valley. . dn: examination of the fallout maps reveals that fallout during this period was associated with the soutismsterly winds, which carried debris from the tropical regions. It is significant that this fallout was independent of precipitation. The highest fallout values occurred during the first three days of the period when there was no precipitation, and even on the 18th, when there were severel stations reporting precipitation, the fallout occurred in the region dominated by the southwesterly winds and was not closely associated with the existence of precipitation. A somewhat similar series of events occurred in the period March 21-25, although precipitation was more widespread in this case and may have had more influence on the observed fallout patterns. 2.2 ROMEO The second burst of the Castle series, Romeo, also a high-yield burst of the same order of magnitude es the Bravo test, was detonated from a barge st 1830 GCT, March 26, 1954. The resulting cloud of debris reached to 110,000 feet, with the base of the mushroom top at 62,000 feet. The wind observations associated with this burst showed light easterly winds at virtually all levels increasing in speed above 80,000 feet to a maximum of 92 knots from the SE at the top of the highest observation, 95,000 feet. Although the trajectories (Figure. 2.3) at all levels in the troposphere moved westward initially, the 30,000- and 0,000-foot trajectories curved northward -~ J =