306
FEELY AND BAZAN
the data from Mildura, Australia (34°S latitude), which are presented
in
Fig.
3. In this figure the "Sr concentrations measured in balloon
samples collected at 65,000 to 70,000 ft and at about 105,000 ft are
plotted.
PTA TTT TTT TTT TTT
34°
@ 105,000 FT
A 70,000 FT
_
te
3
© 65,000 FT
a 10
a
Zz3
2
>
c
=
o
=
= ie
<
s5
ttbebeirs Miri bsp
JFMAMJSASONDSFMAMJJASONDJFMAMJJASOND
1962
1963
1964
Fig. 3—Trends in "Sy activity.
At 65,000 to 70,000 ft, there was no great increase in the *"Sr con-
centrations at Mildura until the second half of 1963, although new
debris from the 1962 United States tests (indicated by the presence of
short-lived fission products) reached Mildura by August 1962. Between
June and August, 1963, the "Sr concentration at 65,000 to 70,000 ft
increased severalfold, only to decrease again after November 1963.
Data from Project Star Dust, which willbe discussed later, suggest that
most of the rise in *Sr concentrations observed during late 1963 re-
sulted from the southward movement of nuclear debris from the northern hemisphere. The subsequent drop in concentrations may have
resulted from a decrease in exchange rates of air between the northern
and the southern hemispheres because of a seasonal change in patterns
of stratospheric circulation.
At 105,000 ft at Mildura, the "Sr concentration rose during late
1962. The debris that was appearing at Mildura at that time contained
‘SCd, as reported by Salter;® therefore some, and perhaps most, of the
new debris may be attributed to the high-altitude Starfish Prime rocket