On the Global Exchange of Mass between the Stratosphere and Troposphere

Seasonal mean downward mass fluxes across the 100 mb level in the extratropics of both hemispheres are computed using the meridionally integrated residual vertical circulation as determined from the transformed Eulerian mean equations. The eddy momentum and heat flux data required for the calculation are taken from Oort's 15-year climatology. Upward mass flux from the troposphere to the stratosphere in the tropics is computed from mass continuity. The flux is a maximum during Northern Hemisphere winter and a minimum during Northern Hemisphere summer. The computed fluxes imply a 2.5 year turnover time for the global atmospheric layer above 100 mb.