Radioactive debris as a tracer for investigating stratospheric motions

Two meteorologically interesting radioactive tracers, Cd-109 injected in 1962 at 400 km by a rocket-borne nuclear device and Pu-238 resulting from the reentry burnup in 1964 of a nuclear powered satellite in the 40–60 km altitude range, are examined and compared with the results of the Rh-102 experiment conducted in 1958. Although detonated at 17° N, the maximum concentration of Cd-109 was detected by the highaltitude balloon samples collected at 34° S. It first appeared at the highest altitude sampled, 32 km, and subsequently seemed to propagate downward at about 1.5 km per month. A second similar surge of Cd-109 was observed at 34° S about a year later. Maximum concentration of Pu-238 also occurred at 32 km at 34° S. Slightly lower concentrations were observed at this altitude in northern temperate and polar regions while concentrations near the equator were an order of magnitude lower. Although the Pu-238 distribution could result from either diffusive mixing along sloping surfaces or from meridional transport, the two surges of Cd-109 suggest poleward transport and subsequent reinforcement from a polar reservoir.