METEOROLOGICAL INFLUENCES ON sr CONCENTRATIONS
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Fig. 5—Fractional change in°Sr concentration, SC, as a function of
Fractional change in ceiling, AH. (AC = 1,25 AH + 0.65.)
the variability in drop size distributions, and the errors associated
with low frequency of ceiling measurement and long sample times are
considered, it is indeed surprising to see anuncertainty in the exponent
of only 50%.
The effect of evaporation has also been observed in Pacific
cyclones. In many cases very dry air overrides the shallow marine
layer, and the first rain falling from the middle clouds accompanying
an approaching wave falls through about 6000 ft of air with a relative
humidity of 30% or less. The Santa Barbara collection of Feb. 7, 1962,
shows this effect markedly.“ A cross section of this storm is shown
in Fig. 6, and the vertical distribution of temperature and humidity
before and after saturation of the marine layer is shown in Fig. 7.
During the first few hours after rain began, the dry air between 2000
and 7500 ft gradually reached saturation. The first rainfall reaching
the ground contained a high Sr concentration, which decreased to onethird of its initial value 2 hr later,
Precipitation-growth Mechanisms The role of this mechanism in determining
ground-level nuclear-debris concentrations has been given earlier.