Sulfur Chemistry in the Antarctic Troposphere Experiment: An overview of project SCATE

In January and February 1994 the Sulfur Chemistry in the Antarctic Troposphere Experiment (SCATE), a multi-institutional field research project, was conducted at Palmer Station (64 degrees 46'S, 64 degrees 03'W), Antarctica. In this paper we describe the scientific background and major objectives of SCATE and present an overview of the field measurement program, the study site, and meteorological conditions prevailing during the experiment. A specific goal of the SCATE study was to improve the current understanding of the chemistry of dimethylsulfide (EMS) in the remote marine atmosphere and its relation to the climate of Antarctica. The SCATE campaign included for the first time measurements of hydroxyl radical (OH), gas phase sulfuric acid (H2SO4), methanesulfonic acid (MSA), and nitric oxide (NO) concentrations over Antarctica. Because of the high time resolution and sensitivity of the corresponding measurement techniques it was possible to distinguish between meteorological and chemical processes contributing to the distribution of DMS oxidation products at the study site. Strong vertical exchange processes and long-range transport of marine air masses frequently dominated the observed concentrations. These processes were governed by intensive low-pressure cells passing through the Drake Passage and circling around the Antarctic coastline.