Fission Product Gamma Activity with Northerly Winds and with Southerly Winds

The gamma ray activity of particulate matter filtered from air samples of northerly winds and of southerly winds has been studied during the period October 1961 to May 1963 with a scintillation spectrometer. It was found that the gamma activity at 0.75, 0.49, and 0.145 Mev was greater when the wind was southerly than when the wind was northerly during the months December through May; the opposite was true from June through September. The gamma ray activity was least during the summer of 1962, the decrease being more pronounced for southerly winds than for northerly winds. These results can be accounted for by modifying the Brewer-Dobson theory of stratospheric circulation so that during most of the year stratospheric debris first reaches the ground south of latitude 40 degrees N. No diurnal effect on the gamma ray activity of the samples could be detected.