Estimates of mass absorption cross sections of black carbon for filter-based absorption photometers in the Arctic
- 1Institute for Space–Earth Environmental Research, Nagoya University, Nagoya, Aichi, Japan
- 2Institute for Advanced Research, Nagoya University, Nagoya, Aichi, Japan
- 3Department of Physics, Faculty of Science Division I, Tokyo University of Science, Tokyo, Japan
- 4National Institute of Polar Research, Tokyo, Japan
- 5Climate Chemistry Measurements Research/Climate Research Division, Environment and Climate Change Canada/Government of Canada
- 6Finnish Meteorological Institute, Helsinki, Finland
- 7Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO, USA
- 8NOAA Global Monitoring Laboratory, 325 Broadway, Boulder, CO, USA
- 9Department of Environmental Science and Analytical Chemistry (ACES), Atmospheric Science Unit, Stockholm University, Stockholm, Sweden
- 10Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan
- 11Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Kanagawa, Japan
- 12Graduate School of Maritime Sciences, Kobe University, Kobe, Japan
- 13Air Quality Research Center, University of California, Davis, CA, USA
- 14Meteorological Research Institute, Tsukuba, Japan
- These authors contributed equally to this work.
Abstract. Long-term measurements of black carbon (BC) are warranted for investigating changes in its emission, transport, and deposition. However, depending on instrumentation, parameters related to BC such as aerosol absorption coefficient (babs) have been measured instead. Most ground-based measurements of babs in the Arctic have been made by filter-based absorption photometers, including multi-angle absorption photometers (MAAP), particle soot absorption photometers (PSAP), continuous light absorption photometer (CLAP), and Aethalometers. The measured babs can be converted to atmospheric mass concentrations of BC (MBC) by assuming the value of the mass absorption cross section (MAC = babs/MBC). However, the accuracy of conversion of babs to MBC has not been adequately assessed. Here, we introduce a systematic method for deriving MAC values from babs measured by these instruments and independently measured MBC. In this method, MBC was measured with a filter-based absorption photometer with a heated inlet (COSMOS). COSMOS-derived MBC (MBC (COSMOS)) is traceable to a rigorously calibrated single particle soot photometer (SP2) and the absolute accuracy of MBC (COSMOS) has been demonstrated previously to be about 15 % in Asia and the Arctic. The necessary conditions for application of this method are a high correlation of the measured babs with independently measured MBC, and long-term stability of the correlation slope, which represents the MAC. In general, babs – MBC (COSMOS) correlations were high (r2 = 0.84–0.96 for hourly data) at Fukue in Japan, Barrow in Alaska, Ny-Ålesund in Svalbard, Pallastunturi in Finland, and Alert in Canada, and stable up to for 10 years. We successfully estimated MAC values (11.0–15.2 m2 g−1 at a wavelength of 550 nm) for these instruments and these MAC values can be used to obtain error-constrained estimates of MBC from babs measured at these sites even in the past, when COSMOS measurements were not made. Because the absolute values of MBC in these Arctic sites estimated by this method are consistent with each other, they are applicable to study spatial and temporal variation of MBC and to evaluate performance of numerical model calculations.
Sho Ohata et al.
Sho Ohata et al.
Sho Ohata et al.
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