scholarly journals Supplementary material to "Estimates of mass absorption cross sections of black carbon for filter-based absorption photometers in the Arctic"

2021 ◽  
Author(s):  
Sho Ohata ◽  
Tatsuhiro Mori ◽  
Yutaka Kondo ◽  
Sangeeta Sharma ◽  
Antti Hyvärinen ◽  
...  
Keyword(s):  
Black Carbon ◽  
Cross Sections ◽  
The Arctic ◽  
Absorption Cross ◽  
Mass Absorption ◽  
Supplementary Material

scholarly journals Estimates of mass absorption cross sections of black carbon for filter-based absorption photometers in the Arctic

2021 ◽  
Author(s):  
Sho Ohata ◽  
Tatsuhiro Mori ◽  
Yutaka Kondo ◽  
Sangeeta Sharma ◽  
Antti Hyvärinen ◽  
...  
Keyword(s):  
Black Carbon ◽  
The Arctic ◽  
Spatial And Temporal Variation ◽  
Absorption Cross ◽  
Mass Absorption ◽  
Hourly Data ◽  
The Absolute ◽  
Absorption Photometer ◽  
Mass Concentrations

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.

scholarly journals Estimates of mass absorption cross sections of black carbon for filter-based absorption photometers in the Arctic

2020 ◽  
Author(s):  
Sho Ohata ◽  
Tatsuhiro Mori ◽  
Yutaka Kondo ◽  
Sangeeta Sharma ◽  
Antti Hyvärinen ◽  
...  
Keyword(s):  
Black Carbon ◽  
The Arctic ◽  
Spatial And Temporal Variation ◽  
Absorption Cross ◽  
Model Calculations ◽  
Mass Absorption ◽  
Hourly Data ◽  
The Absolute ◽  
Absorption Photometer

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.

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