Characterization of atmospheric aerosols across Canada from a ground-based sunphotometer network: AEROCAN

Ground-based sunphotometry measurements acquired under clear sky conditions can be used to investigate atmospheric aerosol optical properties. Such measurements are not only important in their own right as a technique for monitoring generic aerosol dynamics, but also represent a direct means of evaluating the contribution of aerosol induced radiative forcing in the modelling of climate change. In this paper we analyze derived aerosol optical properties using datasets from the Canadian AEROCAN (AERosol CANada) sunphotometer network. The AEROCAN network currently includes eight sunphotometers distributed across Canada at sites chosen in order to obtain a diverse sampling of continental, maritime and arctic aerosols. Some of these sites have been operational since 1993 as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). These instruments permit standard and automatic multi-wavelength measurements of solar extinction radiance centred on the solar disk as well as sky radiance scans off the solar disk. These data yields aerosol optical depth, the Ångström exponent, aerosol particle volume size distribution, refractive index, column-averaged single scattering albedo, and precipitable water vapour content. Spatial and temporal trends of these parameters as well as observed inter-correlations are discussed. The results demonstrate the utility and significance of these types of measurements and illustrate the potential applications of networked sunphotometry data.