The diurnal evolution of 222Rn and its progeny in the atmospheric boundary layer during the Wangara experiment J.-F. Vinuesa1, S. Basu2, and S. Galmarini1 1European Commission – DG Joint Research Centre, Institute for Environment and Sustainability, 21020 Ispra, Italy 2Atmospheric Science Group – Department of Geosciences and Wind Science and Engineering Research Center, Texas Tech University, USA
Abstract. The diurnal atmospheric boundary layer evolution of the 222Rn decaying
family is studied using a state-of-the-art large-eddy simulation model. In
particular, a diurnal cycle observed during the Wangara experiment is
successfully simulated together with the effect of diurnal varying turbulent
characteristics on radioactive compounds initially in a secular equilibrium.
This study allows us to clearly analyze and identify the boundary layer
processes driving the behaviour of 222Rn and its progeny concentrations.
An activity disequilibrium is observed in the nocturnal boundary layer due to
the proximity of the radon source and the trapping of fresh 222Rn close
to the surface induced by the weak vertical transport. During the morning
transition, the secular equilibrium is fast restored by the vigorous
turbulent mixing. The evolution of 222Rn and its progeny concentrations
in the unsteady growing convective boundary layer depends on the strength of
Citation: Vinuesa, J.-F., Basu, S., and Galmarini, S.: The diurnal evolution of 222Rn and its progeny in the atmospheric boundary layer during the Wangara experiment, Atmos. Chem. Phys., 7, 5003-5019, doi:10.5194/acp-7-5003-2007, 2007.