Black carbon is a fine-particulate air pollutant, such as soot, that contributes to climate change. It absorbs sunlight, converting it to heat, which can raise temperatures and melt snow and ice. It can also contribute to heart and lung disease in humans. Fortunately, it only persists in the atmosphere for about one week, so any reduction could have an impact on air quality and heating of the atmosphere in a relatively short time.
However, while several instruments in the Arctic measure the mass concentration of black carbon, there has not been a single, standardized examination of their measurements to understand exactly how much black carbon is in the atmosphere until now. An international group of researchers compared black carbon measurements by various light-absorption instruments in the Arctic and found that they were generally highly correlated with the black carbon concentrations measured by COSMOS (continuous soot monitoring system).
They published their results on Oct. 20 in Atmospheric Measurement Techniques.
“Measurements of light-absorbing and light-scattering properties of aerosols are important for constraining their sources, transport and resulting aerosol radiation interactions in the Earth system,” said co-first author Yutaka Kondo, a project professor at the National Institute of Polar Research.
To convert the aerosol absorption coefficients (how much light black carbon particles absorb), to the mass concentrations of black carbon, the conversion factors (the mass absorption cross-section of black carbon) is needed. They can be obtained by dividing the absorption coefficients by the mass concentrations of BC measured by COSMOS.
“However, the accuracy and stability of the mass absorption cross-section have not been fully evaluated, mainly because of a lack of simultaneous and reliable long-term mass concentrations of black carbon in the atmosphere,” Kondo said. “The reliability of the measurements of black carbon concentrations by various types of filter-based absorption photometers in the Arctic was also poorly understood.”
The researchers used COSMOS, which can measure black carbon mass concentration with an accuracy of 15%. According to Kondo, this accuracy is higher than the absorption photometers deployed in Alert, Canada; Utqiaġvik, Alaska; Ny-Ålesund, Svalbard; and Pallas, Finland.
“In this paper, we determined conversion factors to derive black carbon concentrations from the absorption coefficients measured by the seven absorption photometers with accuracies of about 20 to 30% for the first time,” Kondo said, noting the factors depended on the types of the instruments and the locations of the measurements since the relationship between aerosol absorption and concentration can be complicated by co-existing light-absorbing aerosol such as mineral dust.
The conversion factors are further complicated by co-existence of non-black carbon aerosols that influence absorption coefficient by light scattering— however, Kondo said, we have demonstrated high correlation of between the aerosol absorption coefficients and the black carbon concentrations measured by COSMOS at various sites. This correlation provided the reliable conversion factors for the light-absorption instruments.
“Now, we can standardize black carbon data sets obtained so far in the Arctic,” Kondo said. “These data are valuable for understanding the effect of black carbon on the climate in the Arctic. For example, we can validate climate models through comparisons with these data.”
While the standardizing approach works for data obtained in the Arctic, Kondo cautioned that further work is needed before the method can be applied elsewhere in the world.
Contributors include co-first author Sho Ohata, Institute for Space–Earth Environmental Research and Institute for Advanced Research, Nagoya University, Japan; co-first author Tatshuhiro Mori, Makoto Koike and Nobuhiro Moteki, Department of Earth and Planetary Science, Graduate School of Science, the University of Tokyo, Japan; Yugo Kanaya, Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, and Graduate School of Maritime Sciences, Kobe University, Japan; Atsushi Yoshida, Yutaka Tobo and Junji Matsushita, National Institute of Polar Research, Japan; Naga Oshima, Department of Atmosphere, Ocean, and Earth System Modeling Research, Meteorological Research Institute, Japan; Sangeeta Sharma and Daniel Veber, Climate Chemistry Measurements Research, Climate Research Division, Environment and Climate Change Canada; Antti Hyvärinen, Eija Asmi, John Backman and Henri Servomaa, Atmospheric Composition Research Unit, Finnish Meteorological Institute, Finland; Peter Tunved, Radovan Krejci and Paul Zieger, Department of Environmental Science and Bolin Centre for Climate Research, Stockholm University, Sweden; Konstantinos Eleftheriadis and Stergios Vratolis, Environmental Radioactivity Laboratory, Institute of Nuclear and Radiological Science & Technology, Energy & Safety, National Centre for Scientific Research “Demokritos”, Greece; Yongjing Zhao, Air Quality Research Center, University of California, Davis, United States; and Elisabeth Andrews, Cooperative Institute for Research in Environmental Sciences, University of Colorado, United States.
Mori is also affiliated with the Department of Physics at the University of Tokyo of Science. Andrews is also affiliated with the NOAA Global Monitoring Laboratory in the United States.Tobo is also affiliated with the Department of Polar Science, School of Multidisciplinary Sciences, the Graduate University for Advanced Studies, SOKENDAI, Japan.
The Environment Research and Technology Development Fund (JPMEERF20142003, JPMEERF20152005, JPMEERF20172003, JPMEERF20182003, JPMEERF20202003, and JPMEERF20205001) of the Environmental Restoration and Conservation Agency of Japan, the Japanese Ministry of Education, Culture, Sports, Science and Technology, the Japan Society for the Promotion of Science, the Arctic Challenge for Sustainability (ArCS) project (JPMXD1300000000), the Arctic Challenge for Sustainability II (ArCS II) project (JPMXD1420318865), a grant for the Global Environmental Research Coordination System from the Ministry of the Environment, Japan (MLIT1753), the European Union’s Horizon 2020 research and innovation program, the European Metrology Programme for Innovation and Research, the Academy of Finland, the Swedish Environmental Protection Agency and the U.S. Department of Energy Office of Science’s Atmospheric Radiation Measurement user facility supported this research.
About National Institute of Polar Research (NIPR)
The NIPR engages in comprehensive research via observation stations in Arctic and Antarctica. As a member of the Research Organization of Information and Systems (ROIS), the NIPR provides researchers throughout Japan with infrastructure support for Arctic and Antarctic observations, plans and implements Japan's Antarctic observation projects, and conducts Arctic researches of various scientific fields such as the atmosphere, ice sheets, the ecosystem, the upper atmosphere, the aurora and the Earth's magnetic field. In addition to the research projects, the NIPR also organizes the Japanese Antarctic Research Expedition and manages samples and data obtained during such expeditions and projects. As a core institution in researches of the polar regions, the NIPR also offers graduate students with a global perspective on originality through its doctoral program. For more information about the NIPR, please visit: https://www.nipr.ac.jp/english/
About the Research Organization of Information and Systems (ROIS)
The Research Organization of Information and Systems (ROIS) is a parent organization of four national institutes (National Institute of Polar Research, National Institute of Informatics, the Institute of Statistical Mathematics and National Institute of Genetics) and the Joint Support-Center for Data Science Research. It is ROIS's mission to promote integrated, cutting-edge research that goes beyond the barriers of these institutions, in addition to facilitating their research activities, as members of inter-university research institutes.
Atmospheric Measurement Techniques