The Polar Environment Atmospheric Research Laboratory UV-visible Ground-Based Spectrometer: First measurements of O3, NO2, BrO, and OClO columns

The PEARL-GBS (Polar Environment Atmospheric Research Laboratory-Ground-Based Spectrometer) was permanently installed at Eureka, Nunavut (80.05∘N, 86.42∘W) in August 2006 as part of the establishment of PEARL by CANDAC (Canadian Network for the Detection of Atmospheric Change). The instrument is a ground-based, UV-visible, triple-grating spectrometer and is very similar to the UT-GBS (University of Toronto-GBS), which has an 11-year heritage of measurements, including 10 High Arctic field campaigns. From spectra of zenith-scattered sunlight, vertical column densities (VCDs) of ozone and NO2, and differential slant column densities (DSCDs) of BrO and OCIO can be retrieved. The DSCDs and VCDs of ozone and NO2 have been compared to the UT-GBS and a SAOZ (Système d'Analyse par Observations Zénitales) following the protocols established by the UV-visible Working Group of the Network for the Detection of Atmospheric Composition Change (NDACC). The PEARL-GBS and UT-GBS comparisons meet all standards, while the comparisons with SAOZ partially meet the standards. The VCDs from the three instruments agree, on average, to within 4% for ozone and 8% for NO2. The BrO DSCDs from the PEARL-GBS and UT-GBS agree to within 14%. These are within the combined error bars of the instruments. In 2009, the PEARL-GBS and UT-GBS became affiliated with the NDACC measurement programme.