approximation to the actual case. Consideration of the extreme verti- Cal velocities and violent turbulence existing within the cloud before Stabilization makes it appear unlikely that any major fracticnation of particle size would occur within the cloud and stem at early times. lowe ver, any error introduced in the resultant axis of symmetry as a consequence of tnis essuaption would be minor because of tae particular wind situation throushout Shot 1 fallout. 4 (c) A vertical line fron ground zero to the maximum elevation . (d) Tne physical dimensions of tne cloud a: i stem can be of the clou° represents the axis of seynmetry of tne stem and cloud. ' Satisfactorily represented by assuming they define cylinders about the vertical axis of symmetry of the detonation. 2 : The above assumptions defined a simplified model of the Shot 1 cloud from waich, with information obtained experimentally and the com- plete wind data, the particle trajectories were calculated and their - points of intersection with tne surface of the earth determined as weil as were particle transit times. 6.2.3 " Experimental Data Arplied to Model Evaluation The following experimental data were used to complete tnis - analysis: ~ (a) rom the particle size aralysis of the Bikini Atoll and outer iclend atoll fallout, (see Section 5.2) it was determined that . 4 termined to be 2.36 g/cu om as discussed in Section 5.4. (c) The size distribution of the fallout particulate ranged between 2000 and 254% in diameter. (d) The cloud dimensions both vertical and horizontal were obtained by cloud photography. °/ (e) Meteorological data of the variation with height of both the wind direction and speed, and the air temperature were obtained fron tne Task Force Weathér Central. 6.2.4 Determination of Particle Trajectories Fron consideration of the above essumptions and application of the neasured particle data the terminal velocities of the fallout particles were calculated from aerodynamic faliing equations. (See Arpendix E.) The atmosphere was then divided into 500-ft increments fron the surrace to 100,000 ft and tne average wind speed and direction within these increments was determined. Witii knowledge of the rate of fall of the verious size particles and the wind vectors acting on these particles their trajectories were computed. Particles of 2000, 1500, 1009, 750, 500, 375, 250, 230, 150, 100, 75, 50, and 25 BH in diameter were placed at 5000-ft increments in the cloud model. Each particle size at each starting elevation wes then tollowed through the atmosphere. Comprehensive use of the evailable wind data was made in computing the particle trajectories. Effects of both space and time variations on the winds were fully considered. . The upper air data from Eniwetok, Bikini, BL 4 the particulate were almost entirely irregular in shape. (b) The average apparent density of these particles was de-