Articles | Volume 12, issue 15
Atmos. Chem. Phys., 12, 6827–6843, 2012

Special issue: Integrated Land Ecosystem-Atmosphere Processes Study (iLEAPS)...

Atmos. Chem. Phys., 12, 6827–6843, 2012

Research article 01 Aug 2012

Research article | 01 Aug 2012

Combined effects of surface conditions, boundary layer dynamics and chemistry on diurnal SOA evolution

R. H. H. Janssen1, J. Vilà-Guerau de Arellano2, L. N. Ganzeveld1, P. Kabat1,3, J. L. Jimenez4, D. K. Farmer5, C. C. van Heerwaarden6, and I. Mammarella7 R. H. H. Janssen et al.
  • 1Earth System Science and Climate Change, Wageningen University and Research Centre, Wageningen, The Netherlands
  • 2Meteorology and Air Quality Section, Wageningen University and Research Centre, Wageningen, The Netherlands
  • 3International Institute for Applied Systems Analysis, Laxenburg, Austria
  • 4CIRES and Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA
  • 5Department of Chemistry, Colorado State University, Fort Collins, CO, USA
  • 6Max Planck Institute for Meteorology, Hamburg, Germany
  • 7Department of Physics, University of Helsinki, Helsinki, Finland

Abstract. We study the combined effects of land surface conditions, atmospheric boundary layer dynamics and chemistry on the diurnal evolution of biogenic secondary organic aerosol in the atmospheric boundary layer, using a model that contains the essentials of all these components. First, we evaluate the model for a case study in Hyytiälä, Finland, and find that it is able to satisfactorily reproduce the observed dynamics and gas-phase chemistry. We show that the exchange of organic aerosol between the free troposphere and the boundary layer (entrainment) must be taken into account in order to explain the observed diurnal cycle in organic aerosol (OA) concentration. An examination of the budgets of organic aerosol and terpene concentrations show that the former is dominated by entrainment, while the latter is mainly driven by emission and chemical transformation. We systematically investigate the role of the land surface, which governs both the surface energy balance partitioning and terpene emissions, and the large-scale atmospheric process of vertical subsidence. Entrainment is especially important for the dilution of organic aerosol concentrations under conditions of dry soils and low terpene emissions. Subsidence suppresses boundary layer growth while enhancing entrainment. Therefore, it influences the relationship between organic aerosol and terpene concentrations. Our findings indicate that the diurnal evolution of secondary organic aerosols (SOA) in the boundary layer is the result of coupled effects of the land surface, dynamics of the atmospheric boundary layer, chemistry, and free troposphere conditions. This has potentially some consequences for the design of both field campaigns and large-scale modeling studies.

Final-revised paper