Vertical profile of aerosol number
We use observations of total aerosol number concentrations over the remote Pacific and Southern Oceans, interpreted with a global 3-D aerosol microphysics model, to evaluate our understanding of particle formation.
The figure below shows vertical profiles of total aerosol number concentrations. Observed profiles (dashed lines) are averages over a number of field campaigns [Clarke and Kapustin, 2002]. Mean concentrations of ~500 cm-3 are observed in the marine boundary layer increasing to ~5000 cm-3 in the upper troposphere (UT). With a binary H2SO4-H2O nucleation scheme the model (solid lines) reproduces the vertical profile. New particles are formed in the UT then entrained to the lower free troposphere but number concentrations are reduced by coagulational scavenging. The binary H2SO4-H2O nucleation mechanism rarely predicts new particle formation in the MBL due to a strong temperature dependance and warm BL conditions. Read the paper here
The above figure shows simulated (solid line) and observed (dashed line) [Clarke and Kapustin, 2002] vertical profiles of CN concentrations (at standard temperature and pressure) over the Pacific and Southern Oceans.