AEROSOL PRODUCTION AND GROWTH IN THE MARINE BOUNDARY-LAYER

The dependence of cloud condensation nuclei (CCN) production on the ma rine dimethylsulfide (DMS) flux is modeled with a dynamic description of the gas, aerosol, and aqueous phase processes in a closed air parce l. The results support the conclusion reached in previous work with a steady state model that an approximately linear dependence exists betw een CCN concentration and DMS flux under typical remote marine conditi ons. This linearity does not hold for low DMS fluxes (the threshold is typically near 2.5 mu mol m(-2) day(-1)) because the seasalt particle s heterogeneously convert the available SO2 to sulfate inhibiting the creation of new particles. The conditions under which this linear rela tionship holds are investigated by a series of sensitivity studies, fo cusing particular attention on the impact of the timing and frequency of cloud events. We consider the regimes of the model's semiempirical parameters, showing that the uncertainty associated with two such para meters, namely, the nucleation rate scaling factor and the sulfuric ac id accommodation coefficient, is sufficient to change the predicted CC N production due to DMS from over 300 cm(-3) day(-1) to none. This sen sitivity accounts for most of the range of results predicted by previo us models of the DMS-CCN system.