Simulations of condensation and cloud condensation nuclei from biogenic SO2 in the remote marine boundary layer

Abstract

The calculations suggest that under marine boundary layer conditions, biogenic SO2 will commonly lead to the observed levels of CN but not of CCN active at 2% supersaturation; in order to obtain realistic levels of both CN and CCN (2%), more than 3 days of undisturbed homogeneous gas-phase conditions are required. A number of alternative scenarios and mechanisms are therefore discussed that might facilitate the formation of CCN(2%) in the MBL. Of those, two are likely to be relevant: 1) the formation of new particles outside the MBL, with subsequent transport to the MBL, and 2) the occurrence of heterogeneous SO2 → SO4 conversion on newly formed H2SO4-H2O droplets. Inclusion of cloud-induced and ion-induced nucleation in the model does not favor CCN formation. -from Authors