Stratospheric Data
The Pu-239/Sr-90 ratios at 19.2 km and just above the tropopause
are illustrated in Figures 1 and 2
April 1969.
for the period August 1967 through
These figures were constructed from data obtained in Pro-
ject Airstream (5,6,7,8)
and represent the minimum and maximum alti-
tudes routinely sampled in this program.
varies with latitude,
Since the tropopause height
the altitudes in Figure 2 also vary as follows:
Latitude
Altitude
75°N-65°N
12.2 km
6 5°N-36°N
13.7 km
36°N-3 49s
15.2 km
34°s-51°s
13.7 km
Figure 1 shows that at the higher altitude, the Pu-239/Sr-90 was
uniformly less than 2% in both hemispheres, until the debris from the
6th Chinese test of June 1967 was intercepted in the last quarter of
the year.
At this point the ratio rose to greater than 2 but less
than 3% and essentially remained within this range through all of 1968.
The contours suggest that this debris at 19.2 km crossed the equator
into the Southern Hemisphere in the spring of 1968 and influenced the
ratio to as far south as the Airstream sampling network extends,
I - 15
51°s,