The transport of minor atmospheric constituents between troposphere and stratosphere

Measurements of the water vapour content of air in the upper troposphere and lower stratosphere are reviewed. They are interpreted to indicate that significant upward movement of air through a pressure level of about 100 mb, by processes of any scale, occurs only in equatorial latitudes, but they leave uncertain the mechanism of the upward transfer. This implies that contaminants emitted into the atmosphere below this level can reach the upper stratosphere only by way of the equatorial tropopause and after passage through precipitating cloud. The minimum hemispheric exchange of mass through this level is about 10 17 kg per year. The mass balance of several minor atmospheric constituents, naturally or artificially introduced in the surface layers or in the high stratosphere, is shown to be consistent with this minimum mass exchange.