Age estimates of stratospheric air

It is shown that careful consideration of /sup 32/P//sup 7/Be ratios (both isotopes being generated in the atmosphere by cosmic radiation) not only yields information on the stratospheric or tropospheric origin of air masses. These ratios may also be used to determine the residence time in the stratosphere of tropospheric air that underwent upward transport through the tropopause and re-entered the troposphere at a later date. (auth