CHAPTER 5 levcsaten. FALLOUT IN SPECIFIC AREAS 5.1 . INTRODUCTION “The objective of this section is to investigate the meteorological and radiological conditions which resulted in large surface deposition of radioactive debris in specific areas and attempt to estimate the maximm fallout to be expected from future Pacific tests of yields similar to IVI but under different weather conditions. The results of the fallout monitoring program for Operation IVY are contained in Appendix A and a summary of perti- al nent items of thie data are tabulated in Appendix B, 5.2 WESTERN NORTH PACIFIC OCEAN ‘The highest individual gummed paper activity of the entire network was 3,600,000 d/m reported at Iwo Jima five to six days after the MIKE test and was collected during no precipitation. The highest activity from KING, 150,000 d/m was collected at Truk . in rain, two to three days after detonation, In general, the area west of the Marshall Islands reported the Highest activity after each test, an order of magnitude or more greater than other areas. For the most part, these high values were obtained from portions of the atomic cloud which were in the ' trade winds at the time of stabilization. It is not believed that the trade wind layer of the cloud contained mre radioactivity than did any other portion of the cloud, on the contrary, if past experience is any criterion, the mushroom contained much mre radioactivity. Debris from the high troposphere and the stratosphere, however, is collected only after it has settled or diffused dowward through relatively large vertical distances and consequently is widely dispersed. “he normal precipitation of the tropics falls from clouds embedded entirely in the trade winds layer so that scavenging of the upper tropospheric debris is not common. On the other hand, there were no stations at low latitudes east of the test site, consequently there was no positive evidence ‘that the fallout from the upper tropospheric segment of the cloud which moved eastward, contributed only low radioactivity at the surface. _ Trade winds being a deperidsble feature of the ‘tropical circu- lation will always cause a westward drift of the lowsr layers of an oe 29 =