Developing Standardized EBC

Seven IASOA observatories (Alert, Barrow, Pallas, Summit, Tiksi, Station Nord and Ny-Ålesund) monitor aerosol optical properties including concentrations of absorbing equivalent black carbon.  Despite the unique and exciting analysis opportunities afforded to scientists by an Arctic-wide EBC measurement network, comparing data across stations requires caution because diverse filter-based instruments have been deployed. Multi-instrument comparison requires a process of disentangling differences in instrument-reported values in order to get comparable data from each instrument across the network.  Because of the large uncertainty still surrounding the correction schemes for these instruments, absolute EBC values cannot yet be drawn from instrument light attenuation measurements; however, normalized comparisons are possible.  Most EBC observations from IASOA stations demonstrate the expected high EBC loading relative to the annual average in spring and winter, indicative of the well-documented phenomenon of ‘Arctic haze’. Exceptions to this seasonal variability pattern include Summit (3250 m ASL), which follows the pattern suggested by Scheuer et al. (2003) of aerosol loading in the free atmosphere reaching a peak in summer, and Tiksi, which demonstrates high winter EBC loadings because of its proximity to biomass burning and industrial smelting sources. The diverse seasonal variability at each station shows that a network-based collaboration provides necessary insight into the complex spatial distribution of EBC, which is controlled by seasonally driven long-range transport and by regional sources. The Aerosol Working Group is developing standardized EBC and aerosol optical properties data products that will be submitted to the World Data Center for Aerosols (WDCA) hosted at EBAS (http://ebas.nilu.no/.