Abstract
Tritium analysis of daily rainfall during the 1968/69 rainy season in Rhodesia revealed a correlation between air-mass origin and its tritium content. Tritium values of over 100 tritium units were found on all occasions when a north-westerly airstream had brought lower troposphere air to Rhodesia from Angola or the Congo. When the low-level trajectory suggested an Indian Ocean origin in a north-easterly air stream, the tritium values did not exceed 51 T.U. It is thus suggested that a large proportion of the moisture in north-westerly air is of northern hemisphere origin, whereas the north-easterlies originate in the southern hemisphere. The north-easterlies probably form part of an anticyclonic circulation centred just east of Rhodesia, while the north-westerlies appear to constitute part of an equatorial “drift”, having started off as north-easterlies in the northern hemisphere. Analysis of eight years of monthly rainfall samples from Salisbury shows that high tritium values occur during the main rainy season, which is consistent with the airstream explanation.
© 1972 D. L. Mcnaughton, published by Stockholm University Press
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