METEOROLOGICAL INFLUENCES ON “Sr CONCENTRATIONS
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Table 2— INFLUENCES OF PRECIPITATION MECHANISM AND
FRONTAL PASSAGE ON Sr CONCENTRATION
—
Storm
Jan. 12 and 13, 1960
Nov. 28 and 29, 1960
Feb. 28 and Mar. 1, 1961
Mar. 8 and 9, 1961
Increase factor
due to frontal
passage
2.5
3.9
13.3
3.0
Average, pre-U.S.5.R. testing
Sept. 1, 1961
Dec. 9 and 10, 1961
Average, post-U.8.8.R. testing
Sept, 1, 1961
Overall average
12.5
3.0 + 0.5
9.8 + 4.2
2.6
3.5
3.6
2.9
9.4
Dec. 11 and 12, 1961
Jan, 6 and 7, 1962
Fronts and Trough Lines
Increase factor
due to mechanism
change
3,8 +1.0
3.5 1.3
3.3 + 0.4
7.2 + 4.6
Several observations have been made of greater
nuclear-debris concentrations in air near frontal zones and trough
lines. For example, Miyake ef al.”" noted that the concentration
of “Sr increases in the frontal zone of extratropical cyclones. This
phenomenon has been observed in both our Pennsylvania and Pacific
Coast cyclone studies. In five storms examined in the eastern United
States, the Sr concentration following frontal passage increased by
a factor of between 3 and 13. These data are shown in Table 2. In the
Santa Barbara, Calif., cyclone study, an increase by a factor of more
than 10 was noted (see Fig. 6) just prior to the passage of the trough
line at 500 mb.
The concentration change may also be related to the distance from
the collection site to the trough line aloft. Evidence for this relation
was seen in simultaneous collections’? made at Palo Alto and Santa
Barbara during January 1962 when a trough line oriented east—west
moved slowly southward. The “Sr concentration increased at Santa
Barbara and simultaneously decreased at Palo Alto as the trough line
at 500 mb traveled south.
This increase in "Sr concentration in frontal zones may be due to
any of several changing cloud parameters. For example, the vertical
extent of the clouds usually increases in the frontal zone, and the
freezing level may change abruptly. In addition, the existence of dry
layers of recent stratospheric air, as suggested by Danielsen® and
Staley,’ may be responsible for the observed *0Sr-concentration in-
crease,
Stratification of Nuclear Debris
In a given air mass, the vertical distribution
of reactive materials should be a function of the vertical distribution of
stability. Thus in regions where the vertical distributionof eddy mixing