Characterization of aerosols over the North Atlantic Ocean from SeaWiFS

Over four years of SeaWiFS-derived aerosol optical data are analyzed at nine selected sites within the North Atlantic basin. These sites are representative of continental aerosols, mineral (dust) aerosols or a mixture of both. The seasonal cycle of the aerosol optical thickness (AOT; τ 865 ) and the Ångström exponent ( α 510 ) at each site agrees well with longterm climatology records based on independent ground-truth and/or satellite measurements. The dominant feature in the North Atlantic— the outflow of Saharan dust plumes from northwest Africa—is reflected in higher AOT levels and smaller Ångström values (larger aerosol particles), both close to the source region as well as at downwind sites. The aerosol regime along the US east coast consists primarily of small-sized particles (large Ångström) indicative of urban aerosols. The capability to characterize aerosol processes in the North Atlantic as shown here demonstrates that an ocean-color sensor like SeaWiFS can provide a key contribution to the synoptic monitoring of aerosol processes.