698
SESSION IIB DISCUSSION
REITER: If I understand correctly, you are proposing a tool for
investigating,
say, the much thought-about question of water-vapor
transport from the ocean to the atmosphere.
BOLIN: Yes,
DINGLE: Dr. Reiter, I surmised from your report* that your
studies indicate that perhaps a large bulk of the stratospheric debris
that is brought into the troposphere in stable lamina tends to circulate
downward anticyclonically and then into a following cyclonic system
where it may be rained out. Is this a little different from what has
been expressed at other times and places, derived from Danielsen’s
model, that the cyclonic branch of the extruded lamina carries im-
portant amounts of radioactive debris into the leading cyclonic system
to be rained out there? What is your opinion of relative values of
contribution of the two branches of the extruded lamina to the rainout.
REITER: In answering these questions, I should like to emphasize
that the precipitation observed in our case study which you are referring to is more or less incidental. The case as such should still be
treated as being characteristic for dry fallout. I don’t think there is
any disagreement with your impression that dry fallout should occur
from the anticyclonic branch of the jet stream that moves within the
observed stable layer.
The fact that we did have some precipitation in this case was
due to a small disturbance that moved in. However, it was completely |
dry at the locations of some of the stations collecting fallout, as you
may see from the cross-sections presented in the report, Convection
from underneath eventually penetrated this dry contaminated layer.
When the dry layer was tapped from underneath it had already moved
to as low as 900-mb. Thus moist processes helped in the removal of
radioactive debris, but they should not be considered, in this case,
the primary cause of fallout.
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As far as rainout processes are concerned, I agree with you that
the branch of the stable layer which continues to move cyclonically in
the middle troposphere probably is more Significant than the anticyclonic branch. The cyclonic branch of the jet stream overrides the
warm front, and the contaminated air masses therefore could be tapped
to a significant degree by moist and precipitating air masses from
underneath. This, however, is something that we have not yet studied
in detail. Usually moist cases are somewhat neglected because they
are too complicated to be treated by trajectory analysis. Dr. DanielSen, do you have any comments on this discussion.
*E. R. Reiter, Transport Processes in the Atmosphere Leading to Radioactive Fallout Progress Report No. 1, Colorado State University, Department of
Atmospheric Science, Technical Paper No. 58, September 1964.