Artificial radio-activity, ozone and volcanic dust as atmospheric tracers in the Southern Hemisphere

Abstract

The use of artificial radio-activity measurements to study atmospheric transfer processes is particularly attractive in the Southern Hemisphere because of the absence of atomic testing at other than equatorial regions. Observations of volcanic dust at Aspendale (38° S) following the Bali eruption of 1963 show that the bulk of the material arrived in these latitudes after about six months at a height of 20 km. Simple diffusion theory would imply a horizontal transfer coefficient of 4 times 10 9 cm 2 sec −1 . A similar value would be inferred from the initial appearance of artificial radio-activity in rainfall following the 1962 series of atomic tests at the equator. However, stratospheric sampling carried out at Mildura (35° S) indicate the poleward transfer of fission products to be rather complex. The first arrival after about six months is well demonstrated at a height of 18 km; but other, stronger centres of activity appeared at 33 km after 6–9 months, and at 25 km after 12 months. Seasonal effects are observed in all tracers, but with the various maxima occurring at slightly different times of the year, presumably due to the different heights involved in transfer from an equatorial reservoir. DOI: 10.1111/j.2153-3490.1966.tb00252.x