general conclusions appear justified and |arequoted here from the reports just mentioned. a. In spring, aa band of very steady west winds lies on the equator from about 60,000 feet to 85,000 feet. The northern limit in the central Pacific is about 9°N, but there is no data to fix the southern limit. . trade winds. The steadiness compares to the low-level db. Long-wave disturbances probably affect the equatorial westerlies much in the manner of the waves in the high latitude free air westeriies. - G Above and below the stream of steady westerlies the winds are about as variable as the winds of the -Kigh troposphere. d. The general stratospheric pattern of winter westerlies reversing to stmmer easterlies observed in the mid-latitudes appears to extend down to about 10°N. with a narrow zone of transition to the steady equatorial westerlies, at least up to the end of duly. _ |. If the tentative conclusions quoted above are Valid, one would expect a stratospheric cloud of debris to move almost dus east in the colder half of the year. During the warmer half of the year - the motion would still be zonal (more east or west than north or south) but would have almost equal probability of. moving. toward the - east or the west. 6.5 ESTIMATED ‘FALLOUT ALONG CORE OF THE MIKE TRADE WIND CLOUD | The greatest radioactivity on a gummed paper reported during Operation IVY was collected at Iwo Jima on 5 November 1952 during a period of no precipitation. It appears that the core of the MIKE trade wind cloud passed near Iwo Jima during the period this paper was exposed, thereby depositing the maximum fallout likely without rain. This fortuitous situation was used in connection with pertinent meteorological theory to estimate the activity expected te be collected along the core of this clowi, in the absence of precipitation. The estimates are based on“the postulate that the activity. measured at Iwo Jima is absolutely correct and was actually collected during a period’ of no precipitation. In addition, it is assumed that the decrease of activity collected under the core of the cloud (with increasing time) is essentially the effect of turbulent diffusion and radioactive decay. The form of the Fickian. diffusion law indicated that the peak concentration in a diffusing cloud initially decreases at a rate inversely proportion to the 1.5 ogee