RADIOACTIVITY IN THE SOUTHERN STRATOSPHERE 419 45°N in the first half of 1959 suggest an appearance of Orange debris in the polar stratosphere of the northern hemisphere about six months after its production. Unfortunately, even fewer data from the southern hemisphere are available for this period. The presence of Starfish debris at 34°S in December 1962 may be explained by the rapid meridional movement of material at very high altitudes followed by subsidence into the polar stratosphere and circulation toward the equator in the southern-hemisphere summer. The scant !%cq data for mid-1963 at 45°N and 65°N tend to confirm such a distribution pattern. The ab- sence of '°Cd at 31°N in this period probably reflects the relatively slower mixing into low latitudes which occurs in the hemispheric winter. Data for ‘*Rh (Ref. 11) and ‘%Cad concentrations at 31°N in the second spring after the Orange and Starfish shots, respectively, are given in Table 4. The relative concentrations at a given altitude are Table 4— RHODIUM-102 AND CADMIUM-109 AT 25 TO 35°N ABOUT 20 MONTHS AFTER PRODUCTION 102Rh, 10Cq, Altitude, ft dis/min per 10° scf* dis/min per 103 scft 105 ,000 90,000 80,000 65 ,000 130-200 50— 80 20-130 18~—21 10-13 7—12 0-3 Estimated production | 3 Mc 0.25 Mc *As of Aug. 11, 1958. tAs of July 9, 1962. consistent with the estimated production for these tracers: about 3 Mc of '"Rh (Ref. 12) and about 0.25 Mc of !"cd (Ref. 7). The levels of Sr due to Starfish may be determined from the observed 'cq levels and the value for '"ca/*Sr of 3.5 estimated above for this device. Although these "Sr levels may be relatively consistent, they are subject to bias introduced because of the uncertainties in the ratio. At 31°N the fraction of "Sr attributed to Starfish on the basis of this estimated ratio was generally less than a few percent through 1963, increasing to about 10% at 105,000 ft in 1964. For 34°S Starfish *Sr concentrations are given in the last column of Table 3 for comparison with those attributable to the 1961 U.S.S.R. tests. Although debris attributed to both the 25-Mt 1961 U.S.S.R. device and Starfish was present at 105,000 ft in December 1962 and April 1963 at 34°S, significant differences in its distribution in the southern hemi-