BiSIC TECHNIQUES ND FUTURE STUDIZS “The-basic fall-out forccasting technique used cn Operation C.STLE was an adaptation of the methed outlined in ippendix FP of the Effecta of ._ itomic Weapons, revised September 1950s Essentially, this method e-nputes the rectangular coordinates on the surface at which particles will fall from a saries of hoights, provided the winds ot these heights are inow and the time of fall cen be approximated from « consideration of -aerticle sise distribution. The method was simplified to a considerable extent by the successful application of graphical vectorial solutions to tha equaticns and the aseumphion of workable empirical values of particle size (i.c. tins of fall paromoters) following the DOG Suct of Operation GREENHOUSE, .. descrirtion of the technique was contained in the GREBUOUSE Meteorclozical Report. Morerecently, a detailed grariical solution based on the CREENHOUSS method, was published in .ir Weather Service Manual 105-33, "Radicactivity Ground Fall-out.Plot", datod 1 cugust 1991, revieed.ae (HSM 104-33 "Radio~ activity Fall-cat end RDEZ Plote", dated 2 dune 1952 and being currently revised again. 11 of the above are essentially the same method, <iffering primarily in technique. of applicationand in pefinenent of geaputati-ns and assunptiome. iLL gave reasonably accurateresults, pricr to CASTLE, including an aprarent conpetabllity with the shots of Operation IVT. Elaewherc in this report, there are discussions devoted to assumptions, theorics and apparent procfw relative to the validity of pre-C..STLE forecasting tochniques to cope with large yields. Seme of the factors have been resolved on C..STLE; others have not. The predominant unimow, thathas been af leest partially resolved m C.STLE is that arising from questions of the variation of the efficionsy of thie tyre offall~out forecasting with increased yields. Prior to C/STLE, theonly shots were thoae fired under rather umsual circumstances. the first, ,was fired on the trailing edze of a typhoon with a consequent extremely favorable wad pattern, with all levels of the qhoud moving to the northeast. but with ac mecns whatsoever of assessing the aataal fall-out pattern on the watcr.. The second, IVY Me systen. being: that a1), fall-out. wag. errarentiy in the northwest quadrant froa the ERSWEOK grammed sero... cgeinprnomanny 6f the actual downdnd fabbeut pethermware available, Ths, was an aim burst at approximately 1,500 feet, and, alth-ugh detonated er a wind system considered unfavorable for « surface shot at EXCVET, was cherecter= ~ ised ty the usual small’ ancunt of fall<out asecclated with air bursts. ia cheery, there_apreared price to CiSTLE n> reason why tho system shuld not be adequate to cope with the scheduled shots, exept that the efficiency of the system to rredist fall-out beyond about siz hcurs was seriously questioned and the entrapment characteristicg of the troropause level were not. understocd even in general terms, Por C.STLE it was assumed that the period of fall-cut significant from a test and industrial stendard point of view would be on the order of twelve hours. It wae alac assumed that confidence could not reasomably be placed in significant trepring -f D-2 ww ony DCLOSRE