Modeling Boundary Layer Particle Formation
Boundary Layer particle formation has been observed at many sites around the world. However, the impact on regional and global aerosol concentrations is very uncertain. We include an observationally derived particle formation scheme in a global aerosol microphysics model.
The figure below shows aerosol and gas phase species during March and April 2003 at the SMEAR II measurement station in the boreal forest in Finland. BL particle formation explains the rapid increases in total aerosol number which are observed at the station.
(a) Total particle number, observed (thin black line), model with binary homogeneous nucleation (green line), model with BHN and primary emissions (red line), model with primary emissions and BL particle formation (blue line). (b) Sufur Dioxide, observed (thin black line), model (blue line). (c) Gas-phase sulfuric acid, observed (thin black line), model (blue line). (d) Gas-phase monoterpene, observed (black line), model (blue line). (e) Aerosol condensation sink (similar to aerosol surface area), observed (black line), model (blue line).
We show that particle formation events can sustain mean total particle concentrations a factor of 2–8 greater than those resulting from anthropogenic sources of primary organic and black carbon and from particles nucleated in the upper troposphere.
Global distribution of model surface level particle number in March 2003. (a) Modelled particle number with primary emissions and binary homogeneous nucleation. (b) Ratio of particle number with particle formation and primary emissions to the run with primary emissions only. (c) Model CN including only particle formation (no anthropogenic primary emissions). (d) Gas-phase sulfuric acid.
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