HR: 15:10h
AN: A22E-06 [PDF]
TI: Change in Mixing State of the Global Aerosol Since Pre-Industrial Times
AU: * Raes, F
EM: frank.raes@jrc.it
AF: European Commission, Joint Research Centre, Ispra, VA 21020
Italy
AU: Wilson, J
EM: julian.wilson@jrc.it
AF: European Commission, Joint Research Centre, Ispra, VA 21020
Italy
AU: Van Dingenen, R
EM: rita.van-dingenen
AF: European Commission, Joint Research Centre, Ispra, VA 21020
Italy
AB:
The magnitude of the radiative effect of individual chemical aerosol components is sensitive to how they are mixed among the
particles. Using a global chemical transport model we show that the increase in emissions of aerosol particles and their
precursor gases have caused important changes in aerosol formation processes, and hence the aerosol mixing state. Whereas in
pre-industrial times the conversion of gaseous precursors followed by nucleation was the dominant mechanism for particle
production over large parts of the globe, today the direct emission of anthropogenic black carbon particles with subsequent
condensation of condensable material predominates. The latter process has led to particles that are chemically more complex
(more internally mixed) today than in pre-industrial times. We review the measurements that allow us to test the model
calculations. They include direct measurements such as single particle mass spectroscopy, an indirect ones such as tandem
humidity differential mobility analysis. The available measurements seem to confirm the present day predominance of
internally mixed particles, as suggested by the model results. We therefore argue that assessments of the present and future
radiative forcing of aerosols and hence sound climate change mitigation policies, must evaluate changes in the emissions of
individual aerosol components in terms of their effect on the complete aerosol mixture, rather than just that component
alone.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting