460
REITER AND MAHLMAN
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f) 236.48
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2905
Fig. J—Trajectories on the 295°K isentropic surface from Nov. 22,
1962, at 12 GCT to Nov. 23, 1962, at 00 GCT (full lines with arrows)
and on Nov. 23, 1962, from 00 GCT to 12 GCT (broken lines with arvows). Numerical values of Montgomery stream function (units, 10?
cm*/sec*) and of pressure (mb) are given at starting and terminal
points of trajectories (vertical figures are for the first two map times,
and slanting figures are for Nov. 22, 1962, at 00 GCT). The centers of
the hatched bands indicate the probable boundaries of tropopause air.
effects on stratospheric—tropospheric mass exchange. A rather conservative estimate would be that one hemispheric circulation pattern
per month of the nature described suffices to carry the equivalent mass
of the stratosphere north of 45° latitude downward through the tropopause level within one year. Jet streams, therefore, have to be consid-
ered as very powerful mechanisms for vertical exchange processes in
the atmosphere.
Forecasting of Radioactive Fallout
Although no actual forecasts of fallout were attempted in this study,
certain facts brought out during this and previous investigations lend
themselves to prognostic application. Sharply defined regions of concentrated fallout far away from the site of nuclear explosions should
be expected only when high tropospheric or stratospheric air traveling
in a jet stream is able to sink through the vertical extent of the tropo-
sphere in a matter of a very few days. Only a narrow range of potential temperatures allows a quasi-adiabatic mass flow from the tropo-