664
THATCHER, PAYNE, AND CAMERON
significance of the displacement between the South African and the New
Zealand fallout awaits further study.
At northern-hemisphere stations where both tritium and "Sr data
are available, it has been rather consistently observed that the tritium
fallout peaks are delayed behind the *Sr peaks by one or two months.
The “Sr fallout peak is reached around April or May, whereas the
tritium peak is reached around June or July. The tritium peak extends
further into the late summer because of reevaporation effects. No
explanation
for
the
phase
displacement
of
the
rising limb of the
curve (spring) is available at present.
OBSERVATIONS RELATED TO GLOBAL SUBDIVISIONS
Europe and the Mediterranean
Figure 3 shows tritium relations among several northern European
sites. Concentrations in precipitation at the northern Canadian and
European sites showed the most immediate and highest response to
the late October (23-30) weapons tests in 1961. The January 1962
level for Nord was 2580 T.U., the highest measured in that month
anywhere in the world network. Nord has consistently reported the
highest concentrations, probably partly attributable to the low precipitation. Other European stations showed relatively sharp rises
modified principally by the contribution of maritime air. This is
illustrated by the persistently high level of Vienna as compared to
Valentia (Fig. 4). The decrease in 1964 is illustrated by the Vienna and
the Genoa levels.
The Mediterranean-region data are less complete than the continental data (Fig. 5). Still, the same general trends are shown. Con-
centrations of about 200 T.U. were measured in November at Tel
Aviv (W) and in December at Alexandria (IA). The rise of the spring
peak in 1962 appears to be delayed slightly with respect to the European
peak, but apparently the peak reached levels fully as high. This is
based on one measurement of 1755 T.U. (W) for Tirat Yael, Israel
(recorded as Tel Aviv).
In 1963 the beginning of the spring rise for Tel Aviv is two months
behind Vienna, but again the peak value in June is nearly the same. In
1964 the Tel Aviv peak is much lower than the Vienna peak.
The departures from the standard European mid-latitude pattern
for the Tel Aviv data indicate that the Mediterranean has a measurable influence on the tritium fallout pattern. Additional evidence is
obtained by the consideration of results from Antalya (W) and Ankara
(W), Turkey. Antalya is a coastal site, whereas Ankara is situated
approximately 200 miles north at an altitude of 3000 ft. In January and