The model used is not exact, Since in most cases the base surge approaches a given detector as a curved surface; thus, the intensity at a distance h from the closest point on this curved surface would be less than that from the straight leading edge assumed in the model. The rad:us of curvature of the base surge front encountered under actual conditions is so large, however, that the difference between these two Situations is negligible, particularly when the calculated intensities are used only to compute velocity of approach from the rate of rise of the gamma dose rate record. A.4 WIND CORRECTION FACTORS The velocity components of the wind along each of the station radii are tabulated for a number of reported surface winds. A plus sign indicates that the velocity component should be added. to compensate for wind effects; a minus sign indicates the reverse procedure. The official surface winds are 15 knots from 090° T for Wahoo and 20 knots from 050° T for Umbrella. The range of surface winds appearing in the following table was selected after inspecting continuous _ records of the surface wind made at the Eniwetok Weather Station. During Wahoo, the record fluctuates between 080° and 100° T with speeds between 10 and 15 knots, whereas during Umbrella the variation is between 040° and 070° T with speeds between 10 and 20 knots. A fewadditional surface wind records have been included from the USS Rehoboth (AGS-50) for Wahoo and the USS Boxer (LPH-4) for Umbrella. The wind speeds reported by the Rehoboth were consistently lower than those reported bythe Eniwetok weather station and probably should not be used. A.5 PREDICTED RADIATION CONTOURS Prior to Shots Wahoo and Umbrella, the radiation contours resulting both from radioactive debris raining out of the cloud and from upwelling contaminated water were predicted. The contours were calculated from data available prior to Operation Hardtack (References 8, 14, 22, 24, 39, and 40) for helicopter operations over radex areas and are presented in Figures A.4 and A.5. The values were determined by calculating the radiation intensity due to deposited material 3 feet above an infinite plane (Reference 22) and then converting this intensity to that which would be expected at 10 feet over a body of water, assuming thatall activity is retained ina surface layer 2 meters thick. Tne 5-r/hr boundary obtained from these calculations was then moved in hourly increments on the basis of avaiiable current information for the area (Reference 53). Throughout the calculations, all required estimations were purposely chosen So that fields finally obtained could not reasonably be higher than predicted. The predicted data presented must not be mistaken for actual radiation fields observed after either shot. 348 Page 349 was deleted.