As part of the Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) MAGE (Marine Aerosol and Gas Exchange), this series of Eastern Atlantic Experiments (EAE) was an extensive study of the speciation of sulphur and nitrogen in both clean and moderately polluted atmospheres. It involved the measurement of DMS (and other gases) in the ocean and calculation of fluxes into the atmosphere, combined with the measurement of the speciation of sulphur and nitrogen in both gas and size-fractionated aerosol phases. Isotopic measurements will be used to assess the relative importance of the natural and anthropogenic sources of sulphur and nitrogen, as well as the branching ratio of MSA to SO2 in the atmospheric oxidation of DMS. The gas-to-particle conversion process and a detailed study of physical and chemical composition of fine particles in North Atlantic air will provide information leading to a better understanding of "bursts" of new particle formation observed previously at Atlantic coastal sites.
The experiments were carried out in the spring seasons of 1996 and 1997 during the period of maximum DMS production in this ocean area, thus providing a strong natural signal to the atmosphere. Measurements were made both offshore on the RRS. Challenger and at Mace Head, Ireland. In addition, profiles of aerosol size and distribution and trace gases throughout the marine boundary layer were made using the Jetstream aircraft. An integral part of this experiment is modelling via a zero-dimensional time-dependent photochemical box model of an air mass in the marine boundary layer. The 1997 period of measurements (May) coincided with the OXICOA measurements at Mace Head, resulting in a large collaborative experiment.