FY 2017 Evaluation of ground-based black carbon measurements by filter-based photometers at two Arctic sites Sinha, P.R., Y. Kondo, M. Koike, J.A. Ogren, A. Jefferson, T.E. Barrett, R.J. Sheesley, S. Ohata, N. Moteki, H. Coe, D. Liu, M. Irwin, P. Tunved, P.K. Quinn, and Y. Zhao J. Geophys. Res., 122(6), 3544–3572, doi: 10.1002/2016JD025843 (2017) Long-term measurements of the light absorption coefficient (babs) obtained with a particle soot absorption photometer (PSAP), babs (PSAP), have been previously reported for Barrow, Alaska, and Ny-Ålesund, Spitsbergen, in the Arctic. However, the effects on babs of other aerosol chemical species coexisting with black carbon (BC) have not been critically evaluated. Furthermore, different mass absorption cross section (MAC) values have been used to convert babs to BC mass concentration (MBC = babs/MAC). We used a continuous soot monitoring system (COSMOS), which uses a heated inlet to remove volatile aerosol compounds, to measure babs (babs (COSMOS)) at these sites during 2012–2015. Field measurements and laboratory experiments have suggested that babs (COSMOS) is affected by about 9% on average by sea-salt aerosols. MBC values derived by COSMOS (MBC (COSMOS)) using a MAC value obtained by our previous studies agreed to within 9% with elemental carbon concentrations at Barrow measured over 11 months. babs (PSAP) was higher than babs (COSMOS), by 22% at Barrow (PM1) and by 43% at Ny-Ålesund (PM10), presumably due to the contribution of volatile aerosol species to babs (PSAP). Using babs (COSMOS) as a reference, we derived MBC (PSAP) from babs (PSAP) measured since 1998. We also established the seasonal variations of MBC at these sites. Seasonally averaged MBC (PSAP) decreased at a rate of about 0.55 ± 0.30 ng m−3 yr−1. We also compared MBC (COSMOS) and scaled MBC (PSAP) values with previously reported data and evaluated the degree of inconsistency in the previous data. Feature Publications | Outstanding Scientific Publications Contact Sandra Bigley | Help
