Pew &> is the initfal spread parameter (analogous to standard deviation). For altitudes 10,000 thru 40,000 ft, &@> #2 1.9 miles; 50,000 thru 70,000 ft, Bo ws 5.8 miles, (d) Thruout the whole cloud, all radioactive particles are of the same size, end fall at 50,000 ft per hour. (e) ; In each layer, the central particle falls, without diffusion, as directed by the winds, while other particles diffuse horizontally away from the center equally in all directions so that, when the layer arrives on the surface, the distribution about the center is given by Co (9)” © (r) (F) = oa or (8) : where p = So #8, q = r/&, S m total horizontal distance travelled by the cent ral particle, So = 5.2 &g. (The last quantity may be pictured as the horizontal distance back to a fictitious point source of the cloud layer). (f) The dose rate at any point is proportional to the sum of the concentrations from all of the layers as estimated from the preceding forma. 4. Apart from the assumption of a single particle sise this formulation has a number of other ocdvious defects, e.g. a. The sum of the quantities Coap* should be mede proportional to the total radioactive yield of the"bomb," In practice, the final estimtes were adjusted somewhat on account of expected yield. This, in effect, allowed for the influence on Co, but not on ap. b. The estimation of S as total horizontal distance is rather unsatisfactory in local forecasting where the atoll dimensions are not much greater than the height of the cloud, Also, there was no time to find out whether better results could be obtained by COPIED/DOE LANL RC