Abstract
Abstract. CHABLIS (Chemistry of the Antarctic Boundary Layer and the Interface with Snow) was a collaborative UK research project aimed at probing the detailed chemistry of the Antarctic boundary layer and the exchange of trace gases at the snow surface. The centre-piece to CHABLIS was the measurement campaign, conducted at the British Antarctic Survey station, Halley, in coastal Antarctica, from January 2004 through to February 2005. The campaign measurements covered an extremely wide range of species allowing investigations to be carried out within the broad context of boundary layer chemistry. Here we present an overview of the CHABLIS campaign. We provide details of the measurement location and introduce the Clean Air Sector Laboratory (CASLab) where the majority of the instruments were housed. We describe the meteorological conditions experienced during the campaign and present supporting chemical data, both of which provide a context within which to view the campaign results. Finally we provide a brief summary of highlights from the measurement campaign. Unexpectedly high halogen concentrations profoundly affect the chemistry of many species at Halley throughout the sunlit months, with a secondary role played by emissions from the snowpack. This overarching role for halogens in coastal Antarctic boundary layer chemistry was completely unanticipated, and the results have led to a step-change in our thinking and understanding.
Highlights
The Antarctic boundary layer is one of the regions of the world’s atmosphere least affected by human activity
The broad aims for CHABLIS outlined above, were distilled into three specific science foci: i) seasonal studies of oxidant chemistry which considered the potential role for NO3 during polar twilight/night, halogen chemistry during spring and summer, and HOx chemistry during polar summer; ii) year-round studies of the NOy budget aimed at determining the dominant NOy components, how they varied throughout the year, and what this meant both to sources of NOx and to ice core nitrate; iii) air/snow transfer studies, to assess the influence of the snowpack on coastal Antarctic boundary layer chemistry
The instrument used for measuring carbon monoxide was the AeroLaser Fast CO Monitor, Model AL 5001, which employs the technique of vacuum ultra-violet (VUV) fluorescence for determination of CO
Summary
The Antarctic boundary layer is one of the regions of the world’s atmosphere least affected by human activity. In spite of these studies, the detailed chemistry of the Antarctic boundary layer remained little explored, in particular beyond the summer season. CHABLIS (Chemistry of the Antarctic Boundary Layer and the Interface with Snow) was designed to explore the atmospheric chemistry of the Antarctic boundary layer in greater detail and for a longer period of time than had been previously achieved It was a collaborative project between the British Antarctic Survey and research groups from five UK universities, and involved measurements made by an extensive range of chemical analysers as well as numerical modelling (see Table 1). The centre-piece to CHABLIS was a year-long field campaign to carry out measurements of Antarctic boundary layer chemistry and experiments to explore exchange processes between the snowpack and the overlying atmosphere
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