PARTICLE FORMATION DUE TO SO2 OXIDATION AND HIGH RELATIVE-HUMIDITY INTHE REMOTE MARINE BOUNDARY-LAYER

Nucleation in the marine boundary layer affects the distribution of na tural sulfur across the aerosol size spectrum and thus may contribute to marine cloud condensation nuclei (CCN) concentrations and climate f orcing. We investigated how nucleation probability in remote marine ar eas develops under different conditions. Our study suggests that condi tions favorable for particle formation correspond to transitions from moderate to high relative humidities. The highest nucleation probabili ties were associated with transitions that (1) are relatively rapid, ( 2) occur near the local solar noon, and (3) are a result of the coolin g of the air. The probability of these nucleation events occurring is greater under cleaner conditions and is probably more important than t hose associated with precipitation scavenging in remote marine air.