Simulation of the atmospheric concentrations of 210Pb and 7Be and comparison with daily observations at three surface sites

The atmospheric transport of 210Pb and 7Be is simulated by the Laboratoire de Météorologie Dynamique general circulation model, LMDz, driven by ECMWF reanalyses. Daily averaged concentrations collected at three surface stations are compared with numerical results for a 1 year (2004) global simulation. The model, with a resolution of 3.75°×2.5° and 19 levels, succeeds in reproducing daily variations of 210Pb and 7Be concentrations. Figures of merit in time (FMT), quantifying the overlapping of the predicted and observed time series over each month, range from 55% to 70%. Sensitivity studies as well as the analysis of numerical signals allow determining the main physical atmospheric processes characterizing the stations on a daily basis. Concentrations of 210Pb at the three stations are particularly sensitive to scavenging in convective updrafts.