Tuesday, 8 January 2013
Despite numerous studies since the CLAW hypothesis was first suggested in 1987, the extent to which marine dimethyl sulfide (DMS) contributes to marine atmospheric aerosol populations and the ability of those aerosol to act as cloud condensation nuclei (CCN) remains unclear. Here, we present data from a cruise aboard the R/V Knorr in the Northern Atlantic during June-July 2011which passed through areas of relatively high and low phytoplankton biomass. Continuous ambient measurements of aerosol concentration, cloud condensation nuclei (CCN) concentration, aerosol particle size distributions, and seawater and atmospheric dimethyl sulfide (DMS) concentrations were performed simultaneously during the three-week-cruise. Throughout the cruise, CCN concentration was measured at a series of five supersaturation levels and used to derive the critical superstation required for aerosols to activate as CCN. Our preliminary data analysis shows that the maximum atmospheric DMS concentration and the lowest critical supersaturation were both observed on July 6th 7th (UTC). However, while our data suggests that phytoplankton blooms result in increases in aerosol available to act as CCN, other factors, including meteorological conditions and non-marine contributions to the aerosol populations, influence the properties of aerosols and formation of marine clouds. Factors contributing to the cloud-nucleating ability of aerosol particles will be presented and the atmospheric implications discussed.
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