Fallout deposition m the Marshall Islands @ HL Beck er a HYSPLIT model tended to predict a larger TOA than imdicated by actual data, particularly at large distances, possibly a result of small errors m the wind speed mput data, although errors m wind direction vectors and m the debris cloud model could also be partly responsible The actual TOA may also have been shorter than predicted due to ramout from clouds that otherwise would not have reached ground level (Moroz et al 2010) Estimated ‘Cs deposition at each atoll from 135 Because the estimates of ‘Cs deposition were uncertain,a key test of their overall validity was the igh degree of agreement between the cumulative estimated "Cs deposited at each atoll and the total mventories measured many years later This agreement 1s discussed below under “Estimatesoftotal °’Cs deposition from all tests” Uncertainty inCs deposition estimates As discussed, best estrmates of the E12 exposure each test Usmg the various types of measurement data discussed earher, supplemented by calculations from the rate from each test and the resultant '’Cs deposited were made for eachatoll for each of the tests listed m S1mon of available data and the uncertamty mthe ratio of "Cs NOAA-HYSPLIT model, deposition estrmates have been et al (2010a, Table 1) A best estimate of "Cs deposi- made based on available data, HYSPLIT modeling, or imterpolation An uncertamty estimate was assigned to each of these estimates based on the quality and amount to E12 In general, if the estrmates were based on tion was madefrom all available data for each test and eachatoll Results, expressed m Bq m~%,are presented m Table 7 If no actual data were available for a particular multiple sources of consistent measurements, a geomet- observed pattern of fallout measurements madeat nearby atolls When there was reason to suspect the quality of any Measurement data, agam based on the pattern of fallout at nearby atolls, some mital deposition esumates were subsequently modified to achteve better agreement of the total estimated fallout with the measured soil mventory data A mayor problem m making a best estrmate of fallout on a given atoll from the available data was deciding which data were more relable when estates based on different measurements did not agree One problem was that no formation was available on the exact locations of most of the various measurements Someofthe atolls such as Kwayalein are very large and fallout could have varied over the atoll] area Ground survey measurements were generally few m numberand, thus, might not be representative of the average fallout The airplane survey measurements were usually the maximum recorded readmgs during the flyover of the entire questionable measurement, a GSD of 1 8 was assigned atoll, estimates were based on mterpolation based on the atoll However, because of the flight alutude, the measured value, even after correction for altitude, may often be lower than the actual highest ground level value, especially for the smaller islands It 1s also difficult to mterpret data from measurements madeat times of several weeks or moreafter the minal fallout occurred In such cases, heavy local precipitation between the time of deposition and measurement would have resulted m a reduction in the exposure rate as discussed m Bouville et al (2010) The possibility of weatherimg was considered m our assessment of E12 for a particular test or atoll, particularly when the data were obtamed over a several day period or when the Measurements were mconsistent nic standard deviation (GSD) of 1 3 was assigned, 1f the data were sparser or somewhat mconsistent, a GSD of 1 5 was assigned, and if the estimate was based on a The GSDsassigned to the estrmated '’Cs deposition wereidentical to those for E12 unless there was fractionation, m which case the GSDs were mcreased to reflect the large uncertamty m the estrmated "Cs to E12 ratio If no data were available, and an estimate was based on imterpolation of data at nearby atolls, the uncertamty estimate was based on the quality of the data at those atolls and the apparent variability as a function of distance For a few tests, particularly those prior to 1952, no actual momtormg data were available, and all fallout estimates were based on the meteorological modeling Forthose estimates, a GSD of 3 0 wasassignedto reflect the very ugh uncertainty The net uncertamty im thetotal "Cs deposited from all tests at an atoll was calculated assumingal] individual test estmates were uncorrelated The estimated SD m the effective half-life was used to estimate the resultant SD m decay to either 1978 or 1991-1993 The latter was then combined with the estimated uncertainty m the sum of the measured fallout "'Cs to estimate the overall uncertamty m the expected mventory m 1978 or 1991-1993 Estimates of total"Cs deposition from all tests Thetotal °’Cs deposition at each atoll from all tests was summed and the uncertainty estimate m this sum calculated by combinmg the individual uncertamty est- mates The estrmated total "Cs deposited at each atoll from all tests 1s shown in Table 5 of Simon et al (2010a), and a groupmg ofthe atolls mto four categories, based on stmilar magnitudesof cumulative '*’Cs deposition,1s shown im Table8 ofthis paper and m Fig 2 of Simonet al (201 0a) While these categories are relatively distinct m termsofthe