early spring, when the Aleutian lows are farther south. As the western cell of the Pacific high intensifies, more debris can be carried toward the north, so that by the time of the Yankee test (Figures 3.9 and 3.10), in early May, a larger fraction of the fallout occurred in Japan. Presumably, tests in the summer and early fall would result in the greatest contamination of the Japanese Islands, while winter tests would result in the least. Also during the winter months, vcrecipitation in Japan is at a minimum except for a narrow zone on the western slopes. For most of Japan, maximum rainfall occurs during the warm season, with the heaviest rains in Jume and September. . Similarly, in other inhabited regions likely to be most affected by relatively early fallout, Mexico and Central America to the east and the Phillipines to the west of the test area, the dry season occurs in the winter and the rainiest in the warmer months, so that here too, fallout would be at a minimum for winter tests as compared to other seasons. 3.5 MAXIMUM ACTIVITY AT INDIVIDUAL STATIONS The highest fallout reported on sampling day on an individual gummed film at each of the stations of the network is shown in Figures 3.12 and 3.13, together with the burst responsible (figure in parentheses), the number of days after burst that the fallout occurred and the precipitation observed. All activity values are in d/m/ft2 corrected to sampling day. As can be seen, the fifth burst, Yankee, was responsible for the highest activity at most of the stations, The high trovosuheric westerlies were faster, resulting iar a more rapid transport of debris towards the Americas. in addition, the winds in the eastern Pacific were from the west southwest, resulting in the passage of fresh debris over the southwestern and southern states. On the western side of tne Pacific, the normal seasonal increase in intensity of the western portion of the Pacific high-pressure cell and the retreat of the Aleutian low resulted in the transport of Yankee debris towards the Japanese Islands in the lower levels, although the direct trajectories at these levels moved generally eastward,