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Differential Optical Absorption Spectroscopy Trace Gas Measurements in the Canadian High Arctic Using UV-Visible Spectroscopy

A ground-based, zenith-sky, UV-visible triple-grating spectrometer has been deployed at the Polar Environment Atmospheric Research Laboratory (PEARL) in the Canadian High Arctic during polar springtime every year since 1999. This instrument, the University of Toronto Ground-Based Spectrometer (UT-GBS), participated in the Canadian Arctic ACE (Atmospheric Chemistry Experiment) Validation Campaigns since they began in 2004. From the solar scattered-light spectra, ozone and NO2 vertical column densities (VCDs) have been retrieved using the Differential Optical Absorption Spectroscopy (DOAS) technique.
A near-identical spectrometer, the PEARL-GBS, was permanently installed at PEARL in August 2006 as part of the refurbishment of the laboratory by CANDAC (Canadian Network for the Detection of Atmospheric Change). Since then, the instrument has been making continuous measurements, with the exception of during polar night. Vertical columns of ozone and NO2 can be retrieved year-round. A Sun-tracker was installed directly above the PEARL-GBS in 2008, enabling Multi-Axis DOAS (MAX-DOAS) and direct-Sun observations.
In this work, ozone and NO2 VCDs, and OClO differential slant column densities (DSCDs) from both instruments’ zenith-sky measurements are retrieved from 2011 ACE validation campaign data. Preliminary tropospheric BrO and NO2 DSCDs from Max-DOAS measurements are also presented in this work. Compared to the GBS dataset since 1999, remarkably low ozone and NO2 VCDs and high OClO DSCDs were found at PEARL this past winter. These results are shown to be consistent with the location of the polar vortex and low stratospheric temperatures.