Determinations of Altitudes of Atomic Glouds The positions of the tops of the atomic clouds at the time that they reached highest altitude have been calculated in tuo different ways, ’ For XRAY and YOKE DAYS, With the same elevation ungle in either case, the horizamtal distances would have been 19,0 and 21.2 miles, respectively, For ZEBRA DAY, since the cloud could not have reached the tropopause, the estimate of the maximum altitude was more difficult. DAY— on the secon] teat day the altitude af the cloud as calculated from tropopeuse would have been 56,000 feet, one of these positions was determined from the height of the tropopause, the elevation angles, and the azimuth angles. YOKE the upper winds at H-hour ts 50,200 feet, but the height of the cloud if it reached thea Firet, it mos The first position represents the effect of an averuge wind of 34 kmots whereas the second positian necessary to mke an estimate of the position of the cloud top fram its azimuth angle represents the effect of an average wind of 46 mote. and ite most probable direction of movement from thea test site, mots in combined effect of the upper winds would have accounted for the difference in (See page 22,) Then, Theat ia, a difference of 11 or 12 with all three clouds, the second position was determined from the combination of the the’ two positions, It is reasonable to assume that the actual winda at the tine the clond wind vectors and the rate of rise curves. was rising were stronger than the estim:ited winds and that the altitude of the oloud is If, on the chart, these second points fall Close to the firat, it 1s reagorable to aseume that the clouds did reach the altitudes nore nearly 56,000 feet.thin 50,200 fevt. Since it is thought that the XRAY DAY cloud which were weed in calculating the first points, and that for practical purposes the reached the tropopause, it is believed that the YOKE DAY cloud did also,even though there beights used in drawing the rate of rise curves my be considered to be the actual was no visible evidence. heights. more powerful than the IRAT DAY weapon and the temperature lapse rates on the two days were similar. The charts of Eniwetok also provide a comvenient means of showing the loca- This is based on the assumption that the YORE DAY weapon was In further considerations of the YOKE DAY cloud, it will be ssesuesd that the wind carried the cloud to the approximate position of point "C*® and that the cloud tions of test sites, the positions of the observing shipe, and the most probable di- did reach 56,000 feet, rection of movements of the primary misses of the atomio clouds after the tops had However, in other considerations, it will be assumed that the winds which acted on the cloud were the estimated winds, that is, the winds which would reached maximum altitude. have carried the cloud to point "B", For further discussion of the affect of the wind on the TOKE PAY cloud, sea page 3ée XRAY DAY —- Fro the wind vectors and the rate of rise curve the top of the ZEBRA DAY — Because of the cloud projection which rose out of the ZEBRA DAY cloud is onloulated to be 54,000 feet, or below the tropopause which was at 56,000 feet, cloud, it 1# necessary to know the position of both the primary cloud masa and the Nevertheless, because of the plume which formed on this cloud, it is believed that at least some of tha top of the cloud did extend through the tropopeuse. highest part of the cloud projection in order to fully understand the behavior of this As may atomic cloud, When the position of the highest part of the atomic oloud projection is be noted an ths chart, the distance betwean the two positiona which have been calculated computed by either the rate of rise curve and the wind vectors or from its most prob- by using the two different elevations is less than a mile; and the difference in eleva- able poaition on the tusie of the upper wind directions, it ie found to be in approxi- tion as determined by either method of calculation is only 2,000 feet, The discrepancies mately the same place. are sual] enough to have been caused by the manner in which the theodolites were aimed, fore, the maximm altitude of 33,000 fect calculated from this horizontal distance and In further references the XRAY DAY cloud will be regarded aa having reached 56,000 feet. the corresponding elevation angle is likely to be close to the actual elevation of the For either point, the horizontal distance is 11,0 miles. There- highest part of the cloud. It should be noted that the center of thea primary mesa of the cloud 1a estimated to be approximtely a mile behind the top of the cloud projection, The direction of mouvement of the primary mass mst be draw from point "B" instead af from the cloud top as in the case of the XRAY and YORE DAY clouds, -40-