' Preface learance Requl¢d emoatt ication (‘"AOGAllod+ (|; sue d te ih > CRE MW Oils eldALSfteiernteed hn -. By / Tb BE BOES chis saves) _/y The secondary mission of the metecrological staff of Joint Task Force SEVEN was the inplementation of a scientific metecrological program. Yor logistic reasons, this mission was limited to whatever scientific observations could be mde by the wetecrological personnel and equipment already in the test area because of the operational requirements of the Task Force. The program which was planned included docuwentation of al) meteorological reports, observations on the rate of rise and height of the atomic clouds, volume of the clouds, microbarograph observations in order to obtain preliminary estimates of the bombs’ energies, energy estimtes of the bonbe from thermodynamic considerations, cloud trajectory calculations, and investigations of atmospheric turbulent diffusion. All air burets hate produced what have becom known as‘mushroom clouds, How. ‘ ever, the atomic cloude produced IRAY, YOKE, and ZEBRA Days differed in several note“//'~-‘ worthy respects. These differences were due primrily to the differences in energies aye wor released rather than to any mrked differences in properties of the atmosphere. Esti- * mates of energies released by each weapon are outside the scope of thie mper, but a ' ‘CS. better understamiing of the clouds ie possible if the energies are roughly compared. ase sr The XRAY Day weapon appesred to release somewhat more energy than did the air burst at 7 “., Bikini; the YOKE Day voapon wes somewhat more viclent than that of IRAY Days and the ZEBRA Day weapon was perhaps less violent than the ABIE Day bomb. The ZEBRA Day Au ‘ cloud attained a much lower altitude than either the XRAY or the YOKE Day clouds. This report is concerned primarily with the dste shich were collected an the visible atomic clouds. The metacrological observations contained here ere those for the test days only. The surface, upper wind, upper air, and aircraft observations for the entire duration of the Operation SANDSTONE have been collected and will be made avaiisble in a publication with no security classification. The amounts of energy released by the bombe will be considered only insofar as they affect the atomic cloud formations, The wetecrological microbarograph is not a suitable instrument for seasuring pressure wavee from atoaic weapons and other meteorological methods of etudying the energies of the weapons are not conclusive enough to be considered at this time. In this report no attempt will be made to diacuse the radiological or cheaical properties of the clouds, The phenomena described are those which could be seen or photographed. Clouds from air bursts have begun with the same sequence of events. These include the incomparably brilliant flash of an atomic weapon, the condensation clowi, the fireball phenomena, and the mushroom cloud, These phenomena, which were described many times in the reporte of Operation CROSSROADS, were reported at all three tests during Operation SANDSTONE, Differences occurred only in size or degree, Uninformed observers at seventeen, thirteen, and nine miles for the three tests, respectively, saw no marked difference between the major etomic phimosene and could not compare the energies of the weapons. Also, photographs from CROSSROADS and SANDSTONE of the condensation clouds and fireballe look nearly the same. Therefore, no attempt will be wade to describe phenomena which are not noteworthily different from that reported at Bikini. Prior to Operation SANDSTONE, alsost no numerical data bad been collected on atonls clouds. Photographs were the best means of studying atomic cloud behavior, but the Jack of photogrammetric date made this difficult, In particular, no photographs showed the dispersion of the clouds by the upper winds, and very little was imown of the sanner in which atomic clouds were dispersed. Actually, almoet nothing ws Imo about how dust or smoke clouds would be dissipated if carried to high altitudes. Therefore, it wae important that data be obtained not only to determine the differences, if If it bad been possible to establish two theodolites on a base line three to five miles long and make calculations by means of base line triangulation, much of any, dDetween the clouds produced by the three wapons tested, but also to learn about the generel behavior of atomic clouds. Original planning aseuned that photographs would be available throughout the entire life of the visible atomic clouds, but H-hour for all tests was in the early sorning darkness Just prior to dawn, and photographs of the stages of most rapid rise of the clouis were not possible. Photographs show the atomic clouds during the first fifteen to thirty seconds when in the fireball stage, or show the clouds later wheo at about highest altituies, or when being dispersed. The SANDSTONE Operation did not pro- duce platures of rising cloud mushrooms such as were typical of the CROSSROADS Operation. Many cloud pictures were attempted during the first test and the majority were unusable or photographically disappointing, For that reason, fewer clowl pictures were atteapted during the secand test, and almost no cloud pictures were made during the third test. Ae part of the aclentific neteocrologicel program, weather observers were requested to make observations of atomic clouds by means of their theodolites and to use sketches to show points at which the theodolites were aimed or how the clonda were shaped. Alao, they were asked to write verbal descriptions of all atomic phevomens phed, this report observed, As the clouds could be seen and sketched, but not fs the only record of the clouds between the axtinguishing of the fireballs and the time that the highest portions became lighted by the rising sun. To understand this report, it is necessary to know only a few details of the Operation SANDSTONE. Three atomic weapons wore tested. The first tests conducted was tested on 15 April 1948, designated as IRAY DAT; the second wae tested on 1 May 1948, designated as YOKE Day; and the third was tested on 15 May 1948, designated as ZEBRA Day. H-hours were at 0617, 0609, and 0604 hours local time, respectively. All three of the weapons were fired near the tops of identical towers approximtely 200 feet high. Therefore, all bursts were air bursts and the olonds produced were similar to the ABIZ Day cloud at Bikini. the discussion and sore than a few of the charts in this report could Inve been onitted. Such a base line was not possible as all observers were concentrated Eniwetok for simplification of the redlological safety probles. Observers might have been placed on ships outside of the lagoon, but the problem of moving or training such observers did not seem worthwhile in view of the difficulties and the probabilities of obtaining usable data. Much of this report is concerned with describing the methods used for determining the dimensions of the atomic clouds from what is assumed to be a single observation point. Meteorological data such as upper air soundings and upper winds are used to estimate measurements which could normally be obtained by the use or more than one theodolite atation. In view of the continued requirements for atomic cloud date of a matearelogics] nature, and in view of the radiological hasard and difficulties associated with establishing suitable cbeerving sites, thé procedures used in making the fullest possible use of the data obtained at Eniwetok are described in great detail. It was found, when the probles of reporting on the atomic clouds ms ap~ proached, that the wost effective way to describe the clouds and tell how they were affected by metecrological elements, or to tell how the clouds were obeerved, ie by weans of pictorial presentations. Therefore, except for the brief descriptims of the clouds in the beginning, and the conclusicss and recommendations at the end, this report consists of disgrams, charts, aketches, and photographs, Each set of figures or pdotures is preceded by a brief explanation, and then the situation for IRAT, YORE, and ZEBRA Days is illustrated in turn. : The main body of the report is followed by three appendices. These do not describe the atomic clouds, but give additional information pertinent to a study of the clouds. They present, in the order given, a discussion of the observational techniques, working charte, and theodolite datas the weather observations for the test periods; and the metecrological charts for the test periods. ~