RADIOACTIVITY AND POTENTIAL VORTICITY E, F, DANIELSEN , The Penneylvania State University, University‘Bi,Pennsylvania ABSTRACT Continuous records of radioactivity, wind, and temperature made by WB50 aircraft during Project Springfield substantiate the transfer of radioactivity from the stratosphere to the troposphere by tropopause folding. The continuous records are supported by filter samples of radioactivity taken by both WB50 and RB57 aircraft at critical posi- tions relative to the fold. As expected the radioactivity correlates positively with the potential vorticity; thus the latter can be used as a meteorological tracer of stratospheric air. It can also serve as an indicator of radioactivity concentrations when direct measurements are not available. INTRODUCTION Project Springfield was organized to obtain simultaneous measure- ments of atmospheric radioactivity and significant meteorological variables, Simultaneous measurements were essential for testing the validity of two concepts of fundamental importance to the fallout prob- lem, The first concept, based on a folding of the tropopause, assumes that a nonturbulent transport is the major mode of mass exchange between stratosphere and troposphere. The second concept, based on the conservation of potential vorticity, assumes a positive correlation between the concentration of radioactivity and potential vorticity. These concepts predict a layered distribution of radioactivity and ozone in both the troposphere and stratosphere when the potential vorticity is layered. 436