Measurements of stratospheric composition in the Canadian Arctic during spring 1999-2002 using a UV-visible spectrometer

In order to investigate the influence of chemical processes on Arctic ozone loss, we have deployed a UV-visible spectrometer at Environment Canada´s Arctic Stratospheric Observatory (ASTRO), located at Eureka, NT. To date, three years (1999, 2000, and 2001) of zenith-sky observations have been obtained during the crucial winter/spring period when the perturbed conditions leading to chemical ozone depletion develop. Another Arctic campaign took place in winter/spring 2002 in Resolute Bay, NT. During these four Arctic field campaigns, the instrument was used to record zenith-sky spectra that have been analyzed for ozone and NO₂ using differential optical absorption spectroscopy. The retrieved slant column densities have been converted into vertical column densities by means of air mass factors derived from a multiple scattering radiative transfer model. The total ozone columns compare favorably with concurrent ozone measurements, while the NO₂ columns provide new information on the Arctic stratosphere. In this presentation, we describe the UV-visible spectrometer and present the four-year data set of springtime stratospheric measurements.