Calculation of planetary distributions of radon and its long-lived daughter concentrations in the troposphere and lower stratosphere

Abstract

The boundary value problem for the differential equation for mean zonally averaged tracer concentrations in the meridional plane up to 25 km level and from pole to pole is introduced and connected with a model of tracer transport processes in the atmosphere on a global scale. The coefficients of this equation are determined from climatic data on the mean meridional circulation and macroturbulent diffusion. The finite difference analogue of this problem is solved numerically by the method of matrix factorisation, and the annual mean zonally averaged concentration distributions for Rn222, Pb210, and Po210 are obtained for several variants of parameters. The results of the calculation are compared with the published data of isotope concentration measurements in the free atmosphere, and the global intensity of macroturbulent diffusion is estimated. The calculated isotope content in the troposphere and stratosphere of the northern and southern hemispheres and their rates of transport across the equator and through the topopause are briefly outlined.