Additional Meteorological Analyses of Event Smoky, Plumbbob Test Series (Partial)

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" ADDITIONAL METEOROLOGICAL ANALYSES OF SHOT SMOKY, An i n - depth meteorological an aly - sisof Shot Smoky (August 31, 1957) was started during 1966 inthe Plumbbob Test series.Results of the work completed prior to March, 1967 were reported in the last annual that meteorological data provided as a special support for Shot Smoky contained errors. When included in the stream function analysis, these errors resulted in at raje c - tory pattern not consistent with of these data resulted in a real is - tic stream function analysis, and the derived trajectory analysis pro - vid eda cloud travel path in spatial and temporal agreement with an air - craft observation to within a time period of 20 min at a distance of I n summary, i t was shown Research on Shot Smoky this year was directed toward the following To attempt further is en tropic 0 To correlate meteorological observations of precipitation with cloud passage To compare the results of the of close - in fallout on Shot Smoky with manual calculations and the observed fallout pattern. that is en tropic trajectory cal cula - tions were confirmed at770 km t o within a time of 20 min by corre la - tion with an aircraft observation. Further confirmation of this tech - ni que to depict the temporal d is - placement of a debris cloud is now available. Cedar City, Utah i s approximately 310 km from ground zero along the cloud path.lhe portion of the cloud following the 330" e surface was computed t o have arrived at this location at Weather Bureau observer reported the nuclear debris cloud overhead on the 1558 Z August 31 meteorolog - same time, an observer at Delta, Utah reported a nuclear cloud to the south coinciding with the comput ed arrival ,time ofthe 340" e trajectory shown in Figure 1. fallout material in the vicinity o f Rock Springs, Wyoming(3) were higher than those of the surround - ing area by a factor of five,i.e., a hotspot in the pattern.This finding can be attributed to de - ple tion of the nuclear cloud material and subsequent ground de pos i - tion by scavenging mechanisms asso - cia ted with precipitation.Ithas Measurements of the radioactive

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FIGURE1.Is en tropic Trajectories for Shot Smoky.Aug.31,12302 Tire of arrival Ss noted along the paths.

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long been hypothesized and supported Atypical procedure fully defining by experimental programs ,c4 ' , 8, a fallout pattern and the size that when a particulate cloud coin - cide s in space and time with a pre - ci pita ting cloud then the part icu - late s will be depleted from the atmosphere and deposited on the ground. Is en tropic trajectory analyses for Shot Smoky showed that the debris cloud,travelling along the 320° e surface, would arrive at Rock Springs, Wyoming at13to14hr Meteorological observations from the U.S. Weather Bureau station at Rock Springs, Wyoming , as officially at that time. Although specific in - cloud and below - cloud observations of radioactivity are not available, the coincidence of events provides an explanation for the " hotspot. " However, the possibility that this high radiation measurement could have been deposited by previous shots cannot be entirely discounted. (4) One other area where the computed cloud path coincided with a pre ci pi - t ation area was i n North Central Wyoming. The upper air sounding at Lander, Wyoming during nuclear cloud passage indicated that the unstable conditions could have permitted precipitation scavenging up t o by Figure3. However, the lack of radioactivity measurements in this area precludes corroborative evidence separation was developed to include the required computations of mean vector winds for many layers in the atmosphere. These data were then averaged with respect to time' and applied successively to the various particle size fractions, assumed t o fall at constant velocities as a function of particle size until intersection with the ground. The Defense Land Fallout Interpretive was developed to perform these was modified for use in the Univac 1108 and employed to define fall - methods were used for greater d is - t ances). The one condition nec - ess ary for use of the DELFI C model, i.e.,intersection of the ground surface by the fireball, was satis - fied by Shot Smoky. (4) Meteorological input data as measured a t Yucca Flat approximately 2 6 km south of ground zero were used as initial conditions(Figure 4). These vertical profiles of tempera - ture and wind defined an initially stabilized cloud adjusted for wind deformation. The model computed the cloud top to be 12,290 m above sea level, whereas the one avail - able observation placed the top at 11,500m as shown in the following Code (DELFIC) computational model (2) ofthe washout mechanism. Cloud Cloud Cloud Top Bot tom Radius tion of the surface deposition ob served pattern was performed for this study. DASA 12,290m7,983m 4,000 m

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FIGURE4.Plot of Radios on de Report of Pressure, Temperature, Dew Point and Relative Humidity plus Upper Air Wind Report for Yu csu, Nevada, Aug.32,

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t ions considered the wind field defined by the10data points nearest the cloud. These were processed and combined as inputs to the trans - port module, with the particle populat ionas defined by the model. The cloud was moved in accordance to these data until new wind data were entered.This process was continued until the particles were calculated to have intersected the ground o r the particles had passed through the boundary ofthe model. The transport model also has a capability to consider local c ir cula - s is this option caused the program to cycle and resulted in an exces - sive use o f computer time without producing usable results. The option was then removed and a deposition pattern was produced. The deposition patterns produced by the DELFIC(2) computations were compared with the measured values.(31 The following results were obtained : An anomalous low value near Sheep Mountain coincided with the measured value reported by yet, which factors in the DELFIC model calculation are responsible for this result is not known. The computed mid - line coincided with the measured mid - line out the computed mid - line was d e - the measured mid - line. Computed and measured arrival times arein good agreement out yond that point and away from of a s much as 2hr are noted. Consideration of the vertical need for a north - south separation of particle sizes in the pattern as a result of the shear in the wind mean sea level.This is evident in the skewed distribution of the observed time of arrival to the south of the measured mid - line shown i n were compared tothe DELFIC lines were i n good agreement for computed mid - line diverged to a position about5 km to the north of the observed mid - line at 90 km from ground zero. t ions indicate that the < 44u and 44-88 p - size fractions should have been deposited along the southern part of the pattern(Figure10). indicate that the mid - lined epos i - tion for these particle sizes occur rec along the mid - line prediction for as shown in Figures6,7, and 10. One possible explanation for this disagreement between predicted and observed deposition patterns for the The computed and measured midManual and DELFIC model cal cula - In fact, however, the measurements (3)