oath cine . Further evidence that precipitation has an important effect on surface deposition is presented in Figure 6.1. These bar graphs illustrate the frequency of low activity (low activity defined here as less than 100 d/m on counting day) as a fimction _.0f rainfall amounts during the TUMBLER-SNAPrER Operation and during the IVY Operation. The same tendency is evident in all three graphs although it is not as pronounced in the North Pacific. 4n important conclusion which can be drawn from the graphs is ‘that when atomic debris is present in the atmosphere, even after considerable dilution, rain usually brings about deposition on the surface and the greater the rain the more likely is the deposition. The small decrease of frequency with greater rain . ..@mounts in the Pacific is probably a reflection of the fact that a great deal of material was airborne in the Pacific suring°TVY and the generallevel of ary, fallout was large. 6.3. CUMULATIVE FALLOUT The world-wide fallout monitoring network established for Operation IVY makes it possible to estimate the total beta activity deposited on the earth by the two tests. To this end all gummed ' paper activities were extrapolated to 1 January 1953. The sum of these extrapolated activities at each station, which is a measure of the cumllative fallout present on 1 January 1953, was used in deavoatadd a numerical integration of fallout for the entire surface of the earth. Figure 6.2 shows the cumulative fallout at each station for the entire period of record and an analysis of the distribution, based on radiological and meteorological considerations. Total activity, in units of disintegrations per minute per square foot, was computed separately for the North Pacific (shaded area) and the balance of the world. A similar computation was made for the ' fallout assumed to be from the MIKE test only so that the analysis provided totals for MIKE and KING separately. Figure 6.2 shows the total fallout for the entire period of record at each station and the amount contributed by the KING shot. Adjustments and additions to the basic data were necessary for this analysis. First, the collections assigned to KING on the fallout maps (see Appendix A, Figures 4.33 through 4.73) as well as other samples of doubtful origin but thought to be due to KING, were extrapolated to 1 January.on the basis of 15 November. 1952" burst date. Second, many station records were imcomplete -go their totals had to be adjusted upward. Where the station record included radioactive samples before and after the missing period, the missing activity was estimated by linear interpolation.