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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 17, issue 2 | Copyright
Atmos. Chem. Phys., 17, 1061-1080, 2017
https://doi.org/10.5194/acp-17-1061-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 24 Jan 2017

Research article | 24 Jan 2017

Processes controlling the seasonal variations in 210Pb and 7Be at the Mt. Cimone WMO-GAW global station, Italy: a model analysis

Erika Brattich1, Hongyu Liu2, Laura Tositti1, David B. Considine3, and James H. Crawford4 Erika Brattich et al.
  • 1Department of Chemistry “G Ciamician”, Alma Mater Studiorum University of Bologna, 40126 Bologna (BO), Italy
  • 2National Institute of Aerospace, Hampton, VA 23666, USA
  • 3NASA Headquarters, Washington, DC 20546, USA
  • 4NASA Langley Research Center, Hampton, VA 23681, USA

Abstract. We apply the Global Modeling Initiative (GMI) chemistry and transport model driven by NASA's MERRA assimilated meteorological data to simulate the seasonal variations in two radionuclide aerosol tracers (terrigenous 210Pb and cosmogenic 7Be) at the WMO-GAW station of Mt. Cimone (44°12′N, 10°42′E; 2165ma.s.l.; Italy), which is representative of free-tropospheric conditions most of the year, during 2005 with an aim to understand the roles of transport and precipitation scavenging processes in controlling their seasonality. The total precipitation field in the MERRA data set is evaluated with the Global Precipitation Climatology Project (GPCP) observations, and generally good agreement is found. The model reproduces reasonably the observed seasonal pattern of 210Pb concentrations, characterized by a wintertime minimum due to lower 222Rn emissions and weaker uplift from the boundary layer and summertime maxima resulting from strong convection over the continent. The observed seasonal behavior of 7Be concentrations shows a winter minimum, a summer maximum, and a secondary spring maximum. The model captures the observed 7Be pattern in winter–spring, which is linked to the larger stratospheric influence during spring. However, the model tends to underestimate the observed 7Be concentrations in summer, partially due to the sensitivity to spatial sampling in the model. Model sensitivity experiments indicate a dominant role of precipitation scavenging (vs. dry deposition and convection) in controlling the seasonality of 210Pb and 7Be concentrations at Mt. Cimone.

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We apply the GMI chemistry and transport model to simulate the seasonal variations of two radionuclide aerosol tracers (terrigenous 210Pb and cosmogenic 7Be) at the WMO-GAW station of Mt. Cimone during 2005, with an aim to understand the roles of transport and precipitation scavenging processes in controlling their seasonality. Results show a dominant role of precipitation scavenging in controlling the seasonality of 210Pb and 7Be concentrations at Mt. Cimone.
We apply the GMI chemistry and transport model to simulate the seasonal variations of two...
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