Radon activity in the lower troposphere and its impact on ionization rate: a global estimate using different radon emissions
1Max Planck Institute for Meteorology, Hamburg, Germany
2Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, Colorado, USA
3Institute of Radiation Medicine, Fudan University, Shanghai, China
4Australian Nuclear Science and Technology Organisation, Lucas Heights NSW 2234, Australia
5Federal Office for Radiation Protection (BfS), Salzgitter, Germany
6Laboratoire des Sciences du Climat et de l'Environnement, IPSL, CEA, UVSQ, CNRS, Gif-sur-Yvette, France
7Centre for Isotope Research, University of Groningen, Groningen, The Netherlands
8South African Weather Service, Stellenbosch, South Africa
9NOAA Earth System Research Laboratory (ESRL), Boulder, Colorado, USA
*now at: Pacific Northwest National Laboratory, Richland, Washington, USA
Abstract. The radioactive decay of radon and its progeny can lead to ionization of air molecules and consequently influence aerosol size distribution. In order to provide a global estimate of the radon-related ionization rate, we use the global atmospheric model ECHAM5 to simulate transport and decay processes of the radioactive tracers. A global radon emission map is put together using regional fluxes reported recently in the literature. Near-surface radon concentrations simulated with this new map compare well with measurements.
Radon-related ionization rate is calculated and compared to that caused by cosmic rays. The contribution of radon and its progeny clearly exceeds that of the cosmic rays in the mid- and low-latitude land areas in the surface layer. During cold seasons, at locations where high concentration of sulfuric acid gas and low temperature provide potentially favorable conditions for nucleation, the coexistence of high ionization rate may help enhance the particle formation processes. This suggests that it is probably worth investigating the impact of radon-induced ionization on aerosol-climate interaction in global models.