Using Radioactive Tracers to Develop a Model of the Circulation of the Stratosphere

Since 1952 a number of radioactive substances suitable for use as atmospheric tracers have been injected into the stratosphere. Information on large-scale stratospheric processes derived from measurements of strontium-90, carbon-14, tungsten-185, rhodium-102, cadmium-109 and plutonium-238 is summarized. Although the tracer data are too sparse to define an unambiguous model of the large-scale circulation features of the stratosphere, they should not be ignored in the process of constructing models from other considerations. The tracer data indicate a summer-to-winter hemisphere flow above about 37 km and a mean descending motion in the winter stratosphere between 25° and about 70°. Ascending motion occurs near the equatorial tropopause and in the lower winter stratosphere poleward of 70°. Virtually the entire summer stratosphere and the winter stratosphere equatorward of 25° between 18 and 25 km is dominated by mixing processes with no evidence of organized circulations in the meridional plane.