484
LOCKHART, PATTERSON, SAUNDERS, AND BLACK
Spring subsidence or the exchange of stratospheric air, which is primarily a phenomenon of the higher latitudes.
Transequatorial migration of radioactive particulate matter in the
troposphere_is definitely inhibited, as evidenced by the large disparity
in the activity burdens in the two hemispheres which exists for months
at a time and by the large gradient in activity that is invariably observed near the equator. The profiles of the gross beta-activity concentrations as a function of latitude during the corresponding periods
in the springs of 1959 through 1962, shown in Fig. 4, demonstrate that
equatorial crossover is small during the winter—spring season when
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Fig, 4—Profiles of gross beta activity along the 80th meridian during
the month of April in successive years.