Simulation of 210Pb and 7Be scavenging in the tropics by the LMDz general circulation model

The second part of this paper focuses on the new implemented parameterization of convective scavenging. The objective is to interpret mismatches of simulated concentrations with observed data and to determine which transport mechanisms are responsible for peaks of 7Be concentrations recorded at tropical stations. Typical meteorological situations in Polynesia are analyzed in view of convective transport and scavenging of 7Be. In particular, the sensitivity to the location of the South Pacific Convergence Zone is examined on concentrations in Polynesia. Results demonstrate that 7Be plumes are brought downward in the middle atmosphere by large-scale subsidence associated to the subtropical jet, in a 35°-25°S band. At surface, 7Be plumes are associated either to shallow convection or to deep convection with moderate precipitations. Within moderate convective events, surface concentrations are enhanced by surface release due to re-evaporation of precipitations. Most 7Be surface plumes reaching the Polynesian stations are produced locally in the neighborhood of stations and advected over one or two days by surface large-scale winds. The largest mismatches may be attributed to uncertainties in the simulation of precipitations within deep convective cloud systems that develop along troughs.