990 KRUGER, HOSLER, AND MILLER | | | | 40 -— PS HN 0 — @ ARKANSAS - © WEST COAST © PENNSYLVANIA \. A HAWAII O OKLAHOMA 20 EK _ © .~ @ Oo 0 @ >. _ A = 10 os a os x = w 8 *. S S — S = “.O 3S @ & = -. ao —_ “ee a 50.5- DAY HALF-LIFE 4 ~ ow ee e ‘94 —— “eo oe a of 2/1 3/1 4/1 5/) | 6/1 7/1 | _ 8/1 COLLECTION DATE, 1963 Fig. 3—Sr/*Sr ratios averaged for storms sampled in several locations in the United States during 1963 and shown in comparison to the values of Kuroda’ for Arkansas (solid points). half-life of the ratio indicates a well-mixed atmosphere at the precipitation-generating levels with respect to fission-product age, and the intercept at 167 for weapon fission yields!® correspondsto an “apparent detonation date” of Oct. 5, 1962, falling within the latest period of testing. The peak concentrations of the four storms discussed in this report were about 10 times greater than those of 1962; thus they were about 400 times greater than those of 1961, Several features distinguish Sr deposition in precipitation from convective activity. The first is the relatively large concentration changes over short time periods in conjunction with the cell structural features of the clouds, suchas maximum reflectivity values and altitude, presence of high- and/or low-level precipitation, cell boundaries, etc. Another is the proportional dependence of the Sr concentration upon rainfall intensity. This is the reverse of the “Sr dependence observed in large-scale uplift systems, where the concentration generally is inversely proportional to the rainfall intensity when the ceiling remains

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