tropical winds from 20,000: feet or 30,000 feet up to the tropopause
at 55,000 feet are highly variable, but over a period of several
.davs carry material.to the east or west, but at a differentspeed
than the underlying layer. The result is larze shear between these
layers - an important effect because it causes great horizontal
Julietta:
inbbilanentl aide
stretching which in turn exposes large areas to the diffusive action
of atmospheric turbulence.
The rate of dilution by diffusion,
therefore, proceeds much faster than would be the case with no
Stretching. An elongation of the clouds originating from the
continental tests also occurs since there is a change of wind
speed with elevation but the effect is not as dramatic as in the
Facific. In some of the earlier Pacific tests there was evidence
' that the cloud extended from North America to Asia within. a few
days after the burst.
Second, the tropical precipitation is in the form of showers
instead of large areas of continuous rain mre typical of the
‘United States.
It would be very instructive to determine the
. effect of the showery type of rainfall on the gummed paper collec‘ions °
The height of atomic debris affects the resulting deposition:
‘pattern. Tests at the Nevada Proving Grounds rarely penetrate
“«, heaabasietiit
aporeciably into the stratosphere whereas both the MIKE and KING
tests did and the mushroom from MIKE is believed to have been
‘entirely within the stratosphere. It is believed by most meteoro-
dogists that vertical diffusion in the stratcsphere is appreciably
slower than in the troposphere although no quantitative dava is
avallable. If that is true and if the important vertical trans-
‘part is the consequence of vertical diffusion, then the vertical
transport within the stratosphere would be considerably slower
than the transport through the troposphere. The consequence of
the great height of the IVY clouds, therefore, might be to deposit
their debris later than previous atomic clouds and thus produce
more uniform fallout, since there is more time for horizontal
diffusion to operate.
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