Sulfur in the Marine Atmosphere: A Contribution to the Global Tropospheric Chemistry Program

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The atmospheric processes that bring about the conversion of the gases of sulfur dioxide, nitrogen oxides, and organic compounds to water soluble acids and salts are not well understood. Laboratory and field observations have identified chemical processes that can affect and promote these transformations, but the relative importance of the several oxidizing and catalytic systems present in the atmosphere remains largely unknown. Attempts to understand the relationships between gaseous emissions and remotely observed deposition of their oxidation products are frustrated by this lack of knowledge about the fundamental conversion processes occurring in nature. There is currently great interest in clouds as potential "reaction chambers" for the oxidation of gases into less volatile and water soluble compounds. Many fundamental aspects of sulfur chemistry in the remote marine environment are especially poorly understood. The principal goals of the research project are: 1) To measure vertical distributions of sulfur dioxide and dimethylsulfide over the Northeastern Pacific Ocean and to determine the primary factors responsible for the observed distributions; and 2) To determine the relationships between dimethylsulfide, sulfates, cloud condensation nuclei and cloud droplet size distributions in the remote marine environment. The first step in accomplishing these goals will be the development and testing of instrumentation for airborne studies of the sulfur chemistry in the marine atmosphere. Limited airborne measurements over the Northeastern Pacific Ocean will be carried out over the next two years. The results of these studies should add significantly to our knowledge of sulfur in the marine environment and its role in global tropospheric chemistry and climate.