This special section presents results from an interdisciplinary research cruise to the northern tropical Atlantic Ocean, which took place in October--November 2002. The cruise was planned as a pilot study for the international Surface Ocean -- Lower Atmosphere Study (SOLAS) project. This introduction summarizes the goals as well as the hydrographic and atmospheric setting of the expedition. We also present a brief review of the findings published in this section and elsewhere concerning controls on trace gas fluxes and the biogeochemical significance of dust composition and deposition.