Multi-year and Multi-sensor investigations of Aerosol Optical Properties over the Canadian High Arctic

Sunphotometer measurements have been acquired at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka [Nunavut, Canada] since the spring of 2007. These sunphotometers belong to the AEROCAN/AERONET network and are part of Canadian Network for the Detection of Atmospheric Change (CANDAC). Based on seven years (2007-2013) of continuous spring/summer observations, we report results on the seasonal and inter-annual variations of aerosol optical depth (AOD). The spectral AOD data were resolved into fine (sub-micron) and coarse (super-micron) components using the Spectral Deconvolution Algorithm (SDA) and are examined in conjunction with the profiles of aerosol backscatter coefficient and depolarization ratio obtained from the Arctic High Spectral Resolution Lidar (AHSRL) and the CANDAC Raman Lidar (CRL) as well as column concentrations of CO measured using a Bruker Fourier transform spectrometer and SO2 from Brewer spectrometers. The results are analyzed in the context of fine-mode biomass burning and anthropogenic pollution events that occur typically during spring, volcanic events (e.g., the Kasatochi eruption of August 2008 and the Sarychev eruption of June 2009), and coarse mode events (thin clouds, ice crystals and mineral dust). The monthly average fine mode AOD climatology showed a spring to summer decrease, attributable to biomass burning and/or anthropogenic pollution. The AOD variations over Eureka are compared with Sunphotometer measurements made at other high-Arctic sites, including Alert, Resolute Bay, Barrow, Thule, Kangerlussuaq, Ny-Alesund, and Hornsund. Comparisons with pan-Arctic CALIOP maps and the predictions of aerosol transport models were also investigated in order to better understand the spatio-temporal consistencies and inconsistencies of the different data and modeling sets.