Meteorological influences on the thoron (Rn220) content of the atmosphere

With a new equipment allowing the continuous recording of the atmospheric thoron content with a sensitivity of 0.5·10−14 c/1 and a resolution time of 220 sec, thoron was measured at different levels between 1–8 m for several months and related to meteorological variables. By studying the dependence on the wind direction and the increase with height of the thoron concentration we could verify the homogeneity of the thoron exhalation in the near surroundings of the measuring place at Mainflingen. By comparing the decrease of thoron with height with the theory we succeeded in determining the eddy diffusion coefficient K. It was found that, on an average, K increases linearly with height between 1 and 8 m, and that it is proportional to the mean wind velocity u-. The average eddy diffusion coefficients elaborated from the results of thoron measurements are compared with the corresponding diffusion coefficients of momentum having been calculated from the wind profile. DOI: 10.1111/j.2153-3490.1966.tb00279.x