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 Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan
- 4Department of Physics, Faculty of Science Division I, Tokyo University of Science, Tokyo, Japan
- 5National Institute of Polar Research, Tachikawa, Tokyo, Japan
- 6Climate Chemistry Measurements Research/Climate Research Division, Environment and Climate Change Canada/Government of Canada
- 7Finnish Meteorological Institute, Helsinki, Finland
- 8Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO, USA
- 9NOAA Global Monitoring Laboratory, 325 Broadway, Boulder, CO, USA
- 10Department of Environmental Science and Analytical Chemistry (ACES), Atmospheric Science Unit, Stockholm University, Stockholm, Sweden
- 11Environmental Radioactivity Laboratory (ERL), Institute of Nuclear and Radiological Science & Technology, Energy & Safety, National Centre for Scientific Research ‘‘Demokritos’’, 15310 Attiki, Greece
- 12Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Kanagawa, Japan
- 13Graduate School of Maritime Sciences, Kobe University, Kobe, Japan
- 14Air Quality Research Center, University of California, Davis, CA, USA
- 15Department of Polar Science, School of Multidisciplinary Sciences, The Graduate University for Advanced Studies, SOKENDAI, Tachikawa, Tokyo, Japan
- 16Meteorological Research Institute, Tsukuba, Japan
- These authors contributed equally to this work.
Abstract. Long-term measurements of atmospheric mass concentrations of black carbon (BC) are needed to investigate 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 particle soot absorption photometers (PSAP), continuous light absorption photometer (CLAP), Aethalometers, and multi-angle absorption photometers (MAAP). The measured babs can be converted to mass concentrations of BC (MBC) by assuming the value of the mass absorption cross section (MAC; MBC = babs/MAC). 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 regression slope, which is denoted as MACcor (MAC derived from the correlation). In general, babs–MBC (COSMOS) correlations were high (r2 = 0.76–0.95 for hourly data) at Alert in Canada, Ny-Ålesund in Svalbard, Barrow in Alaska, Pallastunturi in Finland, and Fukue in Japan, and stable for up to 10 years. We successfully estimated MACcor values (10.6–15.2 m2 g−1 at a wavelength of 550 nm) for these instruments and these MACcor 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 the study of spatial and temporal variation of MBC in the Arctic and to evaluation of the performance of numerical model calculations.
Sho Ohata et al.
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