. 4 > ‘ that the presence or absence of debris at the ground has little quantitative relation to the amount of radioactive debris that is airborne. This is due to the fact that the surface deposition . ‘ .is largely a function of the precipitation and without precipitation a cloud might pass overhead undetected. Furthermore, the spread rather detailed wind data, it is difficult to separate the growth due to ghear and that arno te AL Ai fF Peoien, T+ would be of great interest to determine the rate of turbulent exchange between the stratosphere and troposphere, but the effect of precipitation in addition to the fact that the initial vertical distribution of debris . ds unknown precludes solution of the problem with the present data. Cf equal interest would be the computation of the gross diffusion - between the northern and southern hemispheres, but adequate data is ‘not available. while it is possible to estimate the fraction of the total debris in the southern hemisphere, this information is still insufficient to determine the coefficient of eddy diffusion across the equator. It must be concluded: that vt present, the meteorological use of radioactive tracers from the Pacific tests has not yet appreciably — improved the understanding of weather processes. fund J bo ent inmscuas of debris is also a function of the wind shear and unless there is