On the Behavior of Short-lived Cosmic Ray Produced Nuclides in the Lower Atmosphere
AbstractSome aspects of short-lived cosmic ray produced nuclides in the lower atmosphere, especially of Na24 , and their qualities as tracers for atmospheric motion are studied. The Na24 production rate has been estimated. The distribution of this nuclide as a function of altitude in the lower atmosphere has been described by a steady state eddy diffusion model. Measurements of Na24 in ground-level air have been carried out. The measured activities varied from 0.07 ·10-3 to 0.28·10-3 dpm/m3 . These figures are in good accordance with the calculated values for reasonable diffusion parameters. Calculations suggest that CRP-nuclides with life-times in the order of a day are useful as tracers for atmospheric motions in the range of eddy diffusion coefficients of about 5·104 to several 106 cm2 sec-1 , and for altitudes below four of five kilometers. Furthermore some relations between the specific radioactivity of rainwater and the specific activity of cloud-level air, with special respect to short-living CRP-nuclides are found. The evaluation of some measurements of Na24 activity in rain water shows good consistency between real atmospheric conditions and calculated values.