Visible spectroscopy at McMurdo Station, Antarctica

Ground-based observations and satellite data confirm that total ozone abundance over Antarctica during the austral spring has decreased by 50 percent during the last 10 years. As participants in the 1986-1987 National Ozone Expedition, the author measured as many stratospheric chemical constituents as possible to obtain a better understanding of chemical and dynamic processes that may contribute to this decline. Data from last austral spring indicate that abundances of ozone-destroying chlorine compounds were about 29 to 50 times greater than anticipated and vary diurnally. Although these data, as well as lower than expected abundances of nitrogen dioxide, are consistent with the theory that enhanced chlorine chemistry is causing the ozone depletion, these findings do not prove that this model is correct. To augment his data base, during austral spring 1987, the author will continue to use ground-based visible absorption spectroscopy to measure the stratospheric column abundances of ozone, nitrogen compounds, and chlorine compounds. This method provides simultaneous measurements of ozone change and the abundances of reactive nitrogen and reactive chlorine species. Possible correlations between simultaneous measurements of these three constituents are valuable for distinguishing between proposed mechanisms of ozone depletion. The author will take measurements using direct light from themore » Sun and Moon or by measuring the scattered light from the zenith sky.« less