Code for calculating the vertical distribution of radon isotopes and theirprogeny in the atmosphere

A one-dimensional time-dependent eddy-transport model is developed for esti mating the vertical distributions of Rn-222, Rn-220 and their progeny, acti vity ratios of progeny to parent, unattached fraction and equilibrium facto r in the Earth's lower atmosphere. The model takes into account radioactive decay, attachment to aerosol particles, recoil, dry deposition, rainout an d washout processes. The turbulent diffusion equations are solved numerical ly using a backward time centred space differencing scheme after choosing a dimensionless logarithmic scale for the vertical coordinate. (C) 2001 Else vier Science B.V. All rights reserved.