Faculty Profiles - OHATA Sho

Evaluation of sample storage methods for single particle analyses of black carbon in snow and ice: Merits and risks of glass and plastic vials for melted sample storage

Ueda, S; Ohata, S; Iizuka, Y; Seki, O; Matoba, S; Matsui, H; Koike, M; Kondo, Y

AEROSOL SCIENCE AND TECHNOLOGY 2025.8

Publisher：Aerosol Science and Technology

Single particle analyses of black carbon (BC) particles in precipitation samples are necessary to elucidate the BC climatic impact attributable to natural and anthropogenic combustion activities. For practical reasons, snow and ice core samples are often melted and stored as liquid in vials before analysis. We evaluated storage methods of samples after melting to assess BC measurement accuracy by transmission electron microscopy (TEM) and a Single Particle Soot Photometer (SP2) combined with a nebulizer. TEM analysis of ultrapure water samples stored in borosilicate glass vials revealed that nebulized particles contained significant amounts of silicate and sodium eluted from glass vials. Because such eluted materials interfere with individual particle observations, plastic vials should be used for TEM analysis. In contrast, mass concentrations and size distributions of BC in snow samples measured by SP2 after 6-week storage as liquid in glass and PET (a plastic) vials were comparable to the initial concentrations and distributions, indicating that interference from glass-eluted materials was negligible for BC measurements by SP2. Repeated measurements of ice core samples revealed that BC mass concentrations and size distributions for both vials remained stable in most of the samples over several months, although significant BC losses occurred in some samples stored in PET vials. The mass concentration vastly decreased (28% on average) after storage for refrozen–thawed snow samples, suggesting it is unsuitable for accurate BC measurement. Our results demonstrate the great importance of vial choice for analyzing nebulized particles, depending on the analytical method and sample storage period. Copyright © 2025 American Association for Aerosol Research.

DOI： 10.1080/02786826.2025.2542900

Integrated aircraft and research vessel observational studies of aerosols and clouds in summer over the western North Pacific Open Access

Koike, M; Kawai, Y; Adachi, K; Aiki, H; Kanaya, Y; Kawai, H; Kita, K; Kondo, F; Koshiro, T; Matsui, H; Miyakawa, T; Miyamoto, A; Miyasaka, T; Miyazaki, Y; Mochida, M; Mori, T; Moteki, N; Murayama, T; Nakamura, H; Ohata, S; Oka, E; Okajima, S; Tobo, Y; Sekizawa, S; Yoshida, A

PROGRESS IN EARTH AND PLANETARY SCIENCE Vol. 12 ( 1 ) 2025.7

Publisher：Progress in Earth and Planetary Science

An integrated observational study of aerosols and clouds was carried out in summer 2022 over the western North Pacific (off the eastern coast of Hokkaido, Japan) using both an aircraft and a research vessel for the first time in this area. The aim of this experiment was to characterize the physical and chemical properties of aerosols and to evaluate the contributions of anthropogenic and natural emissions to cloud condensation nuclei (CCN) and ice-nucleating particle (INP) concentrations. The experiment also aims to examine the vertical structure of low-level clouds, which have high radiative effects, over this region. Here, we present an overview of the experiment and some preliminary results. Onboard the research vessel, suspended particulate matter in seawater was sampled, and the size distributions of dominant particle types (e.g., diatom fragments and organic matter) were determined. By analyzing atmospheric aerosols sampled from aircraft, we derived the number size distributions of dust-like particles in the air far from source regions. The aerosol size distributions, as measured from both the vessel and aircraft, suggested that most of the aerosols that could act as CCN were of anthropogenic origin: The upper-bound estimate of the sea spray aerosol (SSA) contribution to the CCN concentration at altitudes below 1200 m was 23%. Numerical model simulations generally reproduced the observed aerosol number concentrations. The simulations supported the inference from the observation that most CCN over the study area were of anthropogenic origin. Using this model, SSA emissions were estimated to account for 9% of the cloud radiative effect. Cloud observations from aircraft revealed that low-level clouds tended to have an adiabatic vertical structure under cold air advection, whereas under warm air advection, they occasionally had a layered structure. Such diverse vertical structures of low-level clouds are not generally seen in the subtropics. The integrated observations carried out in this study provided a basic picture of aerosols and clouds over the study area in summer. Further research is needed to elucidate the roles of aerosols in cloud formation and the radiation budget under various meteorological conditions within the framework of atmosphere–ocean interactions. (Figure presented.)

DOI： 10.1186/s40645-025-00719-1

Studies of atmospheric climate forcers in the Arctic during the ArCS II project

Koike M., Takigawa M., Morimoto S., Adachi K., Aizawa T., Chandra N., Fujita R., Goto D., Ishidoya S., Ishijima K., Ito A., Kawai K., Kanaya Y., Kim Y., Kinase T., Kondo Y., Machida T., Matsui H., Miyakawa T., Mochida M., Mori T., Moteki N., Murayama S., Ohata S., Oshima N., Patra P.K., Taketani F., Tobo Y., Tohjima Y., Toyoda S., Tsuboi K., Rui O.C., Yahara K., Yamaji K., Yoshida A., Zhu C.

Polar Science 2025.6

Publisher：Polar Science

This paper reviews studies of atmospheric climate forcers, namely, greenhouse gases (GHGs) and aerosols, and their impacts on radiation and clouds in the Arctic during the Arctic Challenge for Sustainability II (ArCS II) project conducted between 2020 and 2024. In GHG research, we measured atmospheric mixing ratios of CO<inf>2</inf>, CH<inf>4</inf>, and N<inf>2</inf>O and their isotope ratios, as well as O<inf>2</inf>/N<inf>2</inf> ratios from the ground, ship (research vessel Mirai), and commercial aircraft over the northern high latitudes. We showed that the rapid increase of CH<inf>4</inf> mixing ratios after ∼2018 could be attributed to elevated microbial CH<inf>4</inf> emissions. The increase of N<inf>2</inf>O after ∼2011 was attributable to an increase of N<inf>2</inf>O emissions from soil treated with chemical fertilizer. In aerosol research, we provided a scientific basis for constructing unified black carbon (BC) datasets in the Arctic and estimated the contributions to Arctic BC from biomass-burning and anthropogenic sources in various regions. We showed the abundance of highly active ice nucleating particles (INPs) increased with rising surface temperatures above 0 °C and evaluated impacts of Arctic dust that serve as INP on clouds. We found that marine biota were likely the sources of cloud condensation nuclei and INPs over the remote Arctic Ocean during periods of high biological activity.

DOI： 10.1016/j.polar.2025.101216

Sensitivity of Wintertime Arctic Black Carbon to Removal Processes and Regional Alaskan Sources Open Access

Ioannidis, E; Law, KS; Raut, JC; Marelle, L; Onishi, T; Andrews, E; Ohata, S; Mori, T; Morris, S; Kondo, Y; Sharma, S; Eleftheriadis, K; Klimont, Z; Soulie, A; Granier, C; Quinn, PK; Pratt, KA

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Vol. 130 ( 7 ) 2025.4

Publisher：Journal of Geophysical Research Atmospheres

Air pollutants are primarily transported from midlatitude emission regions in winter and early spring, leading to elevated concentrations of aerosols, including black carbon (BC), in the Arctic, a phenomenon known as Arctic haze. The Weather Research and Forecasting model coupled with chemistry is used to investigate potential causes of uncertainties in modeling Arctic BC for winter 2014. The model captures observed variability in BC at surface sites, reproducing BC concentrations at Zeppelin but showing a low bias at Tiksi, Alert, and Utqiaġvik/Barrow. The influence of removal processes on model BC biases is explored by switching off dry or wet deposition. Wet deposition, during transport in the North Atlantic storm track, and locally over Svalbard, dominates BC removal at Zeppelin, while wet removal in the Pacific storm track influences BC at Alert and Utqiaġvik/Barrow. Dry removal over Asian source regions and Alaska affects BC at Utqiaġvik/Barrow, and is larger than wet removal at Tiksi due to the proximity of local/regional anthropogenic sources. Regional runs over northern Alaska in late January show improved simulated BC compared to observations at Utqiaġvik/Barrow, in part, due to better resolution of removal processes, and local/regional emissions. Sensitivity runs also show that regional Alaskan sources, notably from the North Slope of Alaska oil fields, may be contributing 30%–50%, on average, to observed BC at Utqiaġvik/Barrow in January and February 2014, with the remainder from outside the region. These findings highlight the importance of local Arctic emissions, and the need for improved emission inventories in the Arctic.

DOI： 10.1029/2024JD042885

Aircraft-Based Observation of Mineral Dust Particles Over the Western North Pacific in Summer Using a Complex Amplitude Sensor Reviewed International journal Open Access

Ohata, S; Moteki, N; Adachi, K; Tobo, Y; Matsui, H; Kita, K; Mori, T; Koike, M

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Vol. 130 ( 5 ) 2025.3

High-resolution analyses of concentrations and sizes of refractory black carbon particles deposited in northwestern Greenland over the past 350 years – Part 2: Seasonal and temporal trends in refractory black carbon originated from fossil fuel combustion and biomass burning Reviewed International coauthorship International journal Open Access

Kumiko Goto-Azuma, Yoshimi Ogawa-Tsukagawa, Kaori Fukuda, Koji Fujita, Motohiro Hirabayashi, Remi Dallmayr, Jun Ogata, Nobuhiro Moteki, Tatsuhiro Mori, Sho Ohata, Yutaka Kondo, Makoto Koike, Sumito Matoba, Moe Kadota, Akane Tsushima, Naoko Nagatsuka, Teruo Aoki

Atmospheric Chemistry and Physics Vol. 25 ( 1 ) page： 657 - 683 2025.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Copernicus GmbH

Abstract. The roles and impacts of refractory black carbon (rBC), an important aerosol species affecting Earth's radiation budget, are not well understood owing to a lack of accurate long-term observations. To study the temporal changes in rBC since the pre-industrial period, we analyzed rBC in an ice core drilled in northwestern Greenland. Using an improved technique for rBC measurement and a continuous flow analysis (CFA) system, we obtained accurate and high-temporal-resolution records of rBC particle size and mass/number concentrations for the past 350 years. Number and mass concentrations, which both started to increase in the 1870s associated with the inflow of anthropogenically derived rBC, reached their maxima in the 1910s–1920s and then subsequently decreased. Backward-trajectory analyses suggest that North America was likely the dominant source region of the anthropogenic rBC in the ice core. The increase in anthropogenic rBC shifted the annual concentration peaks of rBC from summer to winter–early spring. After rBC concentrations diminished to pre-industrial levels, the annual peak concentration of rBC returned to the summer. We found that anthropogenic rBC particles were larger than biomass burning rBC particles. By separating the rBC in winter and summer, we reconstructed the temporal variations in rBC that originated from biomass burning, including the period with large anthropogenic input. The rBC that originated from biomass burning showed no trend in increase until the early 2000s. Finally, possible albedo reductions due to rBC are discussed. Our new data provide key information for validating aerosol and climate models, thereby supporting improved projections of future climate and environment.

DOI： 10.5194/acp-25-657-2025

On the biases of MERRA-2 reanalysis and ground-based measurements of black carbon aerosols over India Reviewed International coauthorship International journal

Malik, A; Aggarwal, SG; Sinha, PR; Kondo, Y; Ohata, S

ATMOSPHERIC POLLUTION RESEARCH Vol. 16 ( 1 ) 2025.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Atmospheric Pollution Research

The precise measurement of black carbon (BC) and assessment of involved biases are very important considering its serious health and climate effects. MERRA-2 reanalysis data (modern-era retrospective analysis for research and applications, version 2) of surface black carbon (SBC) and ground measurements by optical photometers (mostly Aethalometer) have been used widely to study the temporal and spatial variation of BC aerosol over India. However, a significant bias (more than 70%) between MERRA-2 SBC concentration and ground measurements of BC (by Aethalometer, referred as MBC (AE)) was observed by Malik and Aggarwal (2021). In the current study, the possible reasons for this bias are further evaluated by comparing the MERRA-2 SBC and Aethalometer measurements against a reference photometer, i.e., continuous soot monitoring system (COSMOS). Three-year (2020–2022) SBC concentrations of MERRA-2 reanalysis data are compared against simultaneous measurements of BC by COSMOS (MBC (COSMOS)) at a site in Delhi. Additionally, the biases in ground measurements are further investigated by comparing one-month (March 2023) observations of Aethalometer. These comparison results revealed a 40% underestimation in MERRA-2 reanalysis during 2020–2022. The higher underestimation (50%) of SBC during increased biomass emissions months (October to May), in contrast to the 25% underestimation during conventional emissions months (June to September), emphasizes the underestimation of biomass emissions inputs in MERRA-2 SBC reanalysis. The initial large bias between raw data of Aethalometer (MBC (AE-raw) = 1.92–1.98 times MBC (COSMOS)) get reduced significantly when correction due to multiple scattering factor and mass absorption cross-section (MAC) are incorporated to correct the Aethalometer data (MBC (AE-corr) = 1.15–1.18 times MBC (COSMOS)). The findings of this study underscore the need to harmonize the correction methods for multiple scattering and redefine the MAC values for Aethalometer measurements as well as updating the anthropogenic emission inventories in MERRA-2 SBC reanalysis.

DOI： 10.1016/j.apr.2024.102325

Controlling factors of spatiotemporal variations in black carbon concentrations over the Arctic region by using a WRF/CMAQ simulation on the Northern Hemisphere scale Reviewed

Technical note: High-resolution analyses of concentrations and sizes of refractory black carbon particles deposited in northwestern Greenland over the past 350 years – Part 1: Continuous flow analysis of the SIGMA-D ice core using the wide-range Single-Particle Soot Photometer and a high-efficiency nebulizer Reviewed International coauthorship International journal Open Access

Kumiko Goto-Azuma, Remi Dallmayr, Yoshimi Ogawa-Tsukagawa, Nobuhiro Moteki, Tatsuhiro Mori, Sho Ohata, Yutaka Kondo, Makoto Koike, Motohiro Hirabayashi, Jun Ogata, Kyotaro Kitamura, Kenji Kawamura, Koji Fujita, Sumito Matoba, Naoko Nagatsuka, Akane Tsushima, Kaori Fukuda, Teruo Aoki

Atmospheric Chemistry and Physics Vol. 24 ( 22 ) page： 12985 - 13000 2024.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Copernicus GmbH

Abstract. Ice cores can provide long-term records of refractory black carbon (rBC), an important aerosol species closely linked to the climate and environment. However, previous studies of ice cores only analyzed rBC particles with a diameter of < 500 nm, which could have led to an underestimation of rBC mass concentrations. Information on the size distribution of rBC particles is very limited, and there are no Arctic ice core records of the temporal variation in rBC size distribution. In this study, we applied a recently developed improved technique to analyze the rBC concentration in an ice core drilled at the SIGMA-D site in northwestern Greenland. The improved technique, which uses the modified Single-Particle Soot Photometer (SP2) and a high-efficiency nebulizer, widens the measurable range of rBC particle size. For high-resolution continuous analyses of ice cores, we developed a continuous flow analysis (CFA) system. Coupling of the improved rBC measurement technique with the CFA system allows accurate high-resolution measurements of the size distribution and concentration of rBC particles with a diameter between 70 nm and 4 µm, with minimal particle losses. Using this technique, we reconstructed the size distributions and the number and mass concentrations of rBC particles during the past 350 years. On the basis of the size distributions, we assessed the underestimation of rBC mass concentrations measured using the conventional SP2s. For the period 2003–2013, the underestimation of the average mass concentration would have been 12 %–31 % for the SIGMA-D core.

DOI： 10.5194/acp-24-12985-2024

Surface warming in Svalbardmay have led to increases in highly active icenucleating particles Reviewed International coauthorship International journal Open Access

Yutaka Tobo, Kouji Adachi, Kei Kawai, Hitoshi Matsui, Sho Ohata, Naga Oshima, Yutaka Kondo, Ove Hermansen, Masaki Uchida, Jun Inoue, Makoto Koike

Communications Earth & Environment Vol. 5 ( 1 ) page： 516 - 516 2024.9

Yahara K., Yamaji K., Taketani F., Takigawa M., Kanaya Y., Ohata S., Kondo Y., Koike M.

Polar Science 2024.9

Publisher：Polar Science

Black carbon (BC) aerosol, released into the atmosphere from fuel combustion and biomass burning, is known to be an important short-lived climate forcer (SLCF) because it efficiently absorbs solar radiation and directly heats the atmosphere. Because its accumulation on snow and ice promotes their melting, BC is an important driver of warming, particularly in the Arctic region. Observed surface BC concentrations in the Arctic region show typical seasonal variations, increasing during the winter and spring and decreasing during the warmer season with some peak events in few months of summer, along with large interannual variations. The present study investigates the primary factors influencing the differences in the spatiotemporal surface concentrations of BC in the Arctic region by performing a hemispheric-scale air-quality simulation for the years 2015 and 2016. The model reasonably simulates the observed BC concentration levels and their seasonal patterns, as well as their differences between these two years. This study shows that large year-to-year variability in BC-rich air-mass pathways, such as long-range transport from surrounding regions, and besides these air-mass stagnation within the Arctic region, influence the differences in the Arctic BC concentrations between 2015 and 2016. In addition, the Arctic BC concentrations were also controlled by interannual variations in the amount and distribution of emissions due to the size and the location of open fires, including both Asian crop residue burning in spring and boreal forest fires in summer.

DOI： 10.1016/j.polar.2024.101093

Source contribution of black carbon aerosol during 2020–2022 at an urban site in Indo-Gangetic Plain Reviewed International coauthorship International journal

Arpit Malik, Shankar G. Aggarwal, Yutaka Kondo, Baban Kumar, Prashant Patel, Puna Ram Sinha, Naga Oshima, Sho Ohata, Tatsuhiro Mori, Makoto Koike, Khem Singh, Daya Soni, Akinori Takami

Science of The Total Environment Vol. 934 page： 173039 - 173039 2024.7

Interference of sea salt in capture vaporizer-ToF-ACSM measurements of biomass burning organic aerosols in coastal locations Reviewed International coauthorship International journal Open Access

Adhitya Sutresna, Melita Keywood, Clare Paton-Walsh, Jack Simmons, Caleb Mynard, Quang Dang, Michihiro Mochida, Sho Ohata, Sonia Afsana, Bhagawati Kunwar, Kimitaka Kawamura, Ruhi Humphries, Erin Dunne, Jason Ward, James Harnwell, Fabienne Reisen, Kathryn Emmerson, Alan Griffiths, Alastair Williams, Robyn Schofield, Peter Rayner

Environmental Science: Atmospheres Vol. 4 ( 6 ) page： 634 - 644 2024.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry (RSC)

Measurements of biomass burning organic aerosols using the capture vaporizer-ACSM are interfered with by sea salt aerosols, as both have m/z 60 as a marker ion and the capture vaporizer is able to detect refractory particles like sea salt.

DOI： 10.1039/d3ea00171g

Mass absorption cross section of black carbon for Aethalometer in the Arctic Reviewed International coauthorship International journal Open Access

Mohit Singh, Yutaka Kondo, Sho Ohata, Tatsuhiro Mori, Naga Oshima, Antti Hyvärinen, John Backman, Eija Asmi, Henri Servomaa, Franz Martin Schnaiter, Elisabeth Andrews, Sangeeta Sharma, Kostas Eleftheriadis, Stergios Vratolis, Yongjing Zhao, Makoto Koike, Nobuhiro Moteki, P. R. Sinha

Aerosol Science and Technology Vol. 58 ( 5 ) page： 536 - 553 2024.5

Composition and mixing state of individual aerosol particles from northeast Greenland and Svalbard in the Arctic during spring 2018 Reviewed International coauthorship International journal Open Access

Kouji Adachi, Yutaka Tobo, Naga Oshima, Atsushi Yoshida, Sho Ohata, Radovan Krejci, Andreas Massling, Henrik Skov, Makoto Koike

Atmospheric Environment Vol. 314 page： 120083 - 120083 2023.12

Evaluation of a method to quantify the number concentrations of submicron water-insoluble aerosol particles based on filter sampling and complex forward-scattering amplitude measurements Reviewed International journal Open Access

Sho Ohata, Nobuhiro Moteki, Hikaru Kawanago, Yutaka Tobo, Kouji Adachi, Michihiro Mochida

Aerosol Science and Technology Vol. 57 ( 10 ) page： 1013 - 1030 2023.10

Physical and chemical properties of PM1 in Delhi: A comparison between clean and polluted days Reviewed International coauthorship International journal

Arpit Malik, Shankar G. Aggarwal, Bhagawati Kunwar, Dhananjay Kumar Deshmukh, Kritika Shukla, Rishu Agarwal, Khem Singh, Daya Soni, Puna Ram Sinha, Sho Ohata, Tatsuhiro Mori, Makoto Koike, Kimitaka Kawamura, Yutaka Kondo

Science of The Total Environment Vol. 892 page： 164266 - 164266 2023.9

A signature of aged biogenic compounds detected from airborne VOC measurements in the high arctic atmosphere in March/April 2018 Reviewed International coauthorship Open Access

Rupert Holzinger, Oliver Eppers, Kouji Adachi, Heiko Bozem, Markus Hartmann, Andreas Herber, Makoto Koike, Dylan B. Millet, Nobuhiro Moteki, Sho Ohata, Frank Stratmann, Atsushi Yoshida

Atmospheric Environment Vol. 309 page： 119919 - 119919 2023.9

Constraining the complex refractive index of black carbon particles using the complex forward-scattering amplitude Reviewed International journal Open Access

Nobuhiro Moteki, Sho Ohata, Atsushi Yoshida, Kouji Adachi

Aerosol Science and Technology Vol. 57 ( 7 ) page： 678 - 699 2023.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Informa UK Limited

Black carbon is the largest contributor to global aerosol's shortwave absorption in the current atmosphere and is an important positive climate forcer. The complex refractive index, m = m(r) + im(i), the primary determinant of the absorbed and scattered energies of incident radiation per unit volume of particulate material, has not been accurately known for atmospheric black carbon material. An accurate value at visible wavelengths has been difficult to obtain due to the black carbon's wavelength-scale irregularity and variability of aggregate shape, distribution in particle size, and mixing with other aerosol compounds. Here, we present a method to constrain a plausible (m(r), m(i)) domain for black carbon from the observed distribution of the complex forward-scattering amplitude S(0 degrees). This approach suppresses the biases due to the above-mentioned complexities. The S(0 degrees) distribution of black carbon is acquired by performing single particle S(0 degrees) measurements in a water medium after collecting atmospheric aerosols into water. We demonstrate the method operating at lambda = 0.633 mu m for constraining the refractive index of black carbon aerosols in the north-western Pacific boundary layer. From the plausible (m(r), m(i)) domain consistent with the observed S(0 degrees) distributions and the reported range of mass absorption cross-section, we conservatively select 1.95 + 0.96i as a recommendable value of the refractive index for uncoated black carbon at visible wavelengths. The recommendable value is 0.17 larger in m(i) than the widely used value 1.95 + 0.79i in current aerosol-climate models, implying a similar to 16% underestimate of shortwave absorption by black carbon aerosols in current climate simulations.

DOI： 10.1080/02786826.2023.2202243

The four-wavelength Photoacoustic Aerosol Absorption Spectrometer (PAAS-4<i>λ</i>) Reviewed International coauthorship International journal Open Access

Franz Martin Schnaiter, Claudia Linke, Eija Asmi, Henri Servomaa, Antti-Pekka Hyvärinen, Sho Ohata, Yutaka Kondo, Emma Järvinen

Atmospheric Measurement Techniques Vol. 16 ( 11 ) page： 2753 - 2769 2023.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Copernicus GmbH

Abstract. In this paper, the Photoacoustic Aerosol Absorption Spectrometer (PAAS-4λ) is introduced. PAAS-4λ was specifically developed for long-term monitoring tasks in (unattended) air quality stations. It uses four wavelengths coupled to a single acoustic resonator in a compact and robust set-up. The instrument has been thoroughly characterized and carefully calibrated in the laboratory using NO2/air mixtures and Nigrosin aerosol. It has an ultimate 1σ detection limit below 0.1 Mm−1, at a measurement precision and accuracy of 3 % and 10 %, respectively. In order to demonstrate the PAAS-4λ suitability for long-term monitoring tasks, the instrument is currently validated at the air quality monitoring station Pallas in Finland, about 140 km north of the Arctic circle. A total of 11 months of PAAS-4λ data from this deployment are presented and discussed in terms of instrument performance. Intercomparisons with the filter-based photometers of a continuous soot monitoring system (COSMOS), the Multi-Angle Absorption Photometer (MAAP), and Aethalometer (AE33) demonstrate the capabilities and value of PAAS-4λ, as well as for the validation of the widely used filter-based instruments.

DOI： 10.5194/amt-16-2753-2023

Measurement of number and mass size distributions of light-absorbing iron oxide aerosols in liquid water with a modified single-particle soot photometer Reviewed Open Access

Tatsuhiro Mori, Yutaka Kondo, Kumiko Goto-Azuma, Nobuhiro Moteki, Atsushi Yoshida, Kaori Fukuda, Yoshimi Ogawa-Tsukagawa, Sho Ohata, Makoto Koike

Aerosol Science and Technology Vol. 57 ( 1 ) page： 35 - 49 2022.12

The Ny-Ålesund Aerosol Cloud Experiment (NASCENT): Overview and First Results Reviewed International coauthorship Open Access

J. T. Pasquier;R. O. David;G. Freitas;R. Gierens;Y. Gramlich;S. Haslett;G. Li;B. Schäfer;K. Siegel;J. Wieder;K. Adachi;F. Belosi;T. Carlsen;S. Decesari;K. Ebell;S. Gilardoni;M. Gysel-Beer;J. Henneberger;J. Inoue;Z. A. Kanji;M. Koike;Y. Kondo;R. Krejci;U. Lohmann;M. Maturilli;M. Mazzolla;R. Modini;C. Mohr;G. Motos;A. Nenes;A. Nicosia;S. Ohata;M. Paglione;S. Park;R. E. Pileci;F. Ramelli;M. Rinaldi;C. Ritter;K. Sato;T. Storelvmo;Y. Tobo;R. Traversi;A. Viola;P. Zieger

Bulletin of the American Meteorological Society 2022.7

Contrasting source contributions of Arctic black carbon to atmospheric concentrations, deposition flux, and atmospheric and snow radiative effects Reviewed Open Access

Matsui Hitoshi, Mori Tatsuhiro, Ohata Sho, Moteki Nobuhiro, Oshima Naga, Goto-Azuma Kumiko, Koike Makoto, Kondo Yutaka

ATMOSPHERIC CHEMISTRY AND PHYSICS Vol. 22 ( 13 ) page： 8989 - 9009 2022.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Atmospheric Chemistry and Physics

Black carbon (BC) particles in the Arctic contribute to rapid warming of the Arctic by heating the atmosphere and snow and ice surfaces. Understanding the source contributions to Arctic BC is therefore important, but they are not well understood, especially those for atmospheric and snow radiative effects. Here we estimate simultaneously the source contributions of Arctic BC to near-surface and vertically integrated atmospheric BC mass concentrations (MBC-SRF and MBC-COL), BC deposition flux (MBC-DEP), and BC radiative effects at the top of the atmosphere and snow surface (REBC-TOA and REBC-SNOW) and show that the source contributions to these five variables are highly different. In our estimates, Siberia makes the largest contribution to MBC-SRF, MBC-DEP, and REBC-SNOW in the Arctic (defined as >70° N), accounting for 70 %, 53 %, and 41 %, respectively. In contrast, Asia's contributions to MBC-COL and REBC-TOA are largest, accounting for 37 % and 43 %, respectively. In addition, the contributions of biomass burning sources are larger (29 %-35 %) to MBC-DEP, REBC-TOA, and REBC-SNOW, which are highest from late spring to summer, and smaller (5.9 %-17 %) to MBC-SRF and MBC-COL, whose concentrations are highest from winter to spring. These differences in source contributions to these five variables are due to seasonal variations in BC emission, transport, and removal processes and solar radiation, as well as to differences in radiative effect efficiency (radiative effect per unit BC mass) among sources. Radiative effect efficiency varies by a factor of up to 4 among sources (1471-5326 W g-1) depending on lifetimes, mixing states, and heights of BC and seasonal variations of emissions and solar radiation. As a result, source contributions to radiative effects and mass concentrations (i.e., REBC-TOA and MBC-COL, respectively) are substantially different. The results of this study demonstrate the importance of considering differences in the source contributions of Arctic BC among mass concentrations, deposition, and atmospheric and snow radiative effects for accurate understanding of Arctic BC and its climate impacts.

DOI： 10.5194/acp-22-8989-2022

Measurement of Black Carbon in Delhi: Evidences of Regional Transport, Meteorology and Local Sources for Pollution Episodes Reviewed International coauthorship Open Access

Malik Arpit, Aggarwal Shankar G., Ohata Sho, Mori Tatsuhiro, Kondo Yutaka, Sinha Puna Ram, Patel Prashant, Kumar Baban, Singh Khem, Soni Daya, Koike Makoto

AEROSOL AND AIR QUALITY RESEARCH Vol. 22 ( 8 ) 2022.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Aerosol and Air Quality Research

Measurement of particulate matter (PM) constituent such as black carbon (BC) over urban sites is critically important owing to its adverse health and climate impacts. However, the impacts associated with BC are poorly understood primarily because of the scarcity and uncertainties of measurements of BC. Here, we present BC measurement at an urban site of Delhi using a characterized continuous soot monitoring system (COSMOS) for a year-long period, i.e., from September, 2019 to August, 2020. This measurement period covers events, i.e., period of crop residue burnings from nearby states, festive events, e.g., Diwali and New Year, and first COVID-19 lockdown period. Effects of these events combining with local emissions and meteorological conditions on BC mass concentration (MBC) are investigated to find the possible cause of severe pollution levels in Delhi. Mean MBC for the complete observation period was found to be 5.02 ± 4.40 µg m–3. MBC showed significant seasonal as well diurnal variations. Winter season (December to February) is observed to be the most polluted season owing to increased local emissions and non-favorable meteorological conditions. Regional emission from crop burning in nearby states during October and November is the main contributing factor for increased pollution in this post-monsoon season. Furthermore, analysis reveals that cracker burning during festivals can also be considered as contributing factor to high MBC for a short period in post-monsoon and winter seasons. Significant decrease in MBC due to COVID-19 lockdown is also observed. MBC in summer and monsoon are lower as compared to other seasons but are still higher than mean MBC levels in several other urban cities of different countries. Also, the BC data obtained from nearby sites and Modern-Era Retrospective analysis for Research and Applications-version 2 (MERRA-2)’s surface black carbon (SBC) are compared against the MBC to evaluate coherency among the different datasets, and discussed in detail.

DOI： 10.4209/aaqr.220128

Offline analysis of the chemical composition and hygroscopicity of submicrometer aerosol at an Asian outflow receptor site and comparison with online measurements Reviewed International coauthorship Open Access

Deng Yange, Fujinari Hiroaki, Yai Hikari, Shimada Kojiro, Miyazaki Yuzo, Tachibana Eri, Deshmukh Dhananjay K., Kawamura Kimitaka, Nakayama Tomoki, Tatsuta Shiori, Cai Mingfu, Xu Hanbing, Li Fei, Tan Haobo, Ohata Sho, Kondo Yutaka, Takami Akinori, Hatakeyama Shiro, Mochida Michihiro

ATMOSPHERIC CHEMISTRY AND PHYSICS Vol. 22 ( 8 ) page： 5515 - 5533 2022.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Atmospheric Chemistry and Physics

Filter-based offline analysis of atmospheric aerosol hygroscopicity coupled to composition analysis provides information complementary to that obtained from online analysis. However, its application itself and comparison to online analysis have remained limited to date. In this study, daily submicrometer aerosol particles (PM0.95, 50% cutoff diameter 0.95μm) were collected onto quartz fiber filters on Okinawa Island, a receptor of East Asian outflow, in the autumn of 2015. The chemical composition of water-soluble matter (WSM) in PM0.95, PM0.95 itself, and their respective hygroscopicities were characterized through the offline use of an aerosol mass spectrometer and a hygroscopicity tandem differential mobility analyzer. Thereafter, results were compared with those obtained from online analyses. Sulfate dominated the WSM mass (59%), followed by water-soluble organic matter (WSOM, 20%) and ammonium (13%). WSOM accounted for most (91%) of the mass of extracted organic matter (EOM) and the atomic O-to-C ratios (O:C) of WSOM and EOM were high (mean±standard deviation were 0.84±0.08 and 0.78±0.08, respectively), both of which indicate highly aged characteristics of the observed aerosol. The hygroscopic growth curves showed clear hysteresis for most samples. At 85% relative humidity (RH), the calculated hygroscopicity parameter κ values of the WSM (κWSM), WSOM, EOM, and PM0.95 (κPM0.95) were 0.50±0.03, 0.22±0.12, 0.20±0.11, and 0.47±0.03, respectively. An analysis using the thermodynamic Extended Aerosol Inorganics Model (E-AIM) shows, on average, that inorganic salts and WSOM contributed 88% and 12%, respectively, of the κWSM (or κPM0.95). High similarities were found between offline and online analysis for chemical compositions that are related to particle hygroscopicity (the mass fractions and O:C of organics and the degree of neutralization) and also for aerosol hygroscopicity. As possible factors governing the variation in κWSM, the influences of WSOM abundance and the neutralization of inorganic salts were assessed. At high RH (70%-90%), the hygroscopicity of WSM and PM0.95 was affected considerably by the presence of organic components; at low RH (20%-50%), the degree of neutralization could be important. This study not only characterized aerosol hygroscopicity at the receptor site of East Asian outflow but also shows that offline hygroscopicity analysis is an appropriate method, at least for aerosols of the studied type. The results encourage further applications to other environments and to more in-depth hygroscopicity analysis, in particular for organic fractions.

DOI： 10.5194/acp-22-5515-2022

Possible controls on Arctic clouds by natural aerosols from long-range transport of biogenic emissions and ozone depletion events Reviewed International coauthorship

Rupert Holzinger, Oliver Eppers, Kouji Adachi, Heiko Bozem, Markus Hartmann, Andreas Herber, Makoto Koike, Dylan B. Millet, Nobuhiro Moteki, Sho Ohata, Frank Stratmann, Atsushi Yoshida

2022.2

Arctic black carbon during PAMARCMiP 2018 and previous aircraft experiments in spring Reviewed International coauthorship Open Access

Sho Ohata, Makoto Koike, Atsushi Yoshida, Nobuhiro Moteki, Kouji Adachi, Naga Oshima, Hitoshi Matsui, Oliver Eppers, Heiko Bozem, Marco Zanatta, Andreas B. Herber

Atmospheric Chemistry and Physics Vol. 21 ( 20 ) page： 15861 - 15881 2021.11

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Copernicus GmbH

Abstract. Vertical profiles of the mass concentration of black carbon (BC) weremeasured at altitudes up to 5 km during the PAMARCMiP (Polar Airborne Measurements and Arctic Regional Climate Model simulation Project) aircraft-based fieldexperiment conducted around the northern Greenland Sea (Fram Strait) duringMarch and April 2018 from operation base Station Nord (81.6∘ N,16.7∘ W). Median BC mass concentrations in individual altituderanges were 7–18 ng m−3 at standard temperature and pressure ataltitudes below 4.5 km. These concentrations were systematically lower thanprevious observations in the Arctic in spring, conducted by ARCTAS-A in 2008and NETCARE in 2015, and similar to those observed during HIPPO3 in 2010.Column amounts of BC for altitudes below 5 km in the Arctic (>66.5∘ N; COLBC), observed during the ARCTAS-A and NETCAREexperiments, were higher by factors of 4.2 and 2.7, respectively, than thoseof the PAMARCMiP experiment. These differences could not be explained solelyby the different locations of the experiments. The year-to-year variation ofCOLBC values generally corresponded to that of biomass burning activitiesin northern midlatitudes over western and eastern Eurasia. Furthermore,numerical model simulations estimated the year-to-year variation ofcontributions from anthropogenic sources to be smaller than 30 %–40 %.These results suggest that the year-to-year variation of biomass burningactivities likely affected BC amounts in the Arctic troposphere in spring,at least in the years examined in this study. The year-to-year variations inBC mass concentrations were also observed at the surface at high Arcticsites Ny-Ålesund and Utqiaġvik (formerly known as Barrow, the location ofBarrow Atmospheric Baseline Observatory), although their magnitudes were slightlylower than those in COLBC. Numerical model simulations in general successfully reproduced the observedCOLBC values for PAMARCMiP and HIPPO3 (within a factor of 2), whereas theymarkedly underestimated the values for ARCTAS-A and NETCARE by factors of3.7–5.8 and 3.3–5.0, respectively. Because anthropogenic contributionsaccount for nearly all of the COLBC (82 %–98 %) in PAMARCMiP and HIPPO3,the good agreement between the observations and calculations for these twoexperiments suggests that anthropogenic contributions were generally wellreproduced. However, the significant underestimations of COLBC forARCTAS-A and NETCARE suggest that biomass burning contributions wereunderestimated. In this study, we also investigated plumes with enhanced BCmass concentrations, which were affected by biomass burning emissions,observed at 5 km altitude. Interestingly, the mass-averaged diameter of BC(core) and the shell-to-core diameter ratio of BC-containing particles inthe plumes were generally not very different from those in other airsamples, which were considered to be mostly aged anthropogenic BC. Theseobservations provide a useful basis to evaluate numerical model simulations ofthe BC radiative effect in the Arctic region in spring.

DOI： 10.5194/acp-21-15861-2021

Estimates of mass absorption cross sections of black carbon for filter-based absorption photometers in the Arctic Reviewed International coauthorship Open Access

Sho Ohata, Tatsuhiro Mori, Yutaka Kondo, Sangeeta Sharma, Antti Hyvärinen, Elisabeth Andrews, Peter Tunved, Eija Asmi, John Backman, Henri Servomaa, Daniel Veber, Konstantinos Eleftheriadis, Stergios Vratolis, Radovan Krejci, Paul Zieger, Makoto Koike, Yugo Kanaya, Atsushi Yoshida, Nobuhiro Moteki, Yongjing Zhao, Yutaka Tobo, Junji Matsushita, Naga Oshima

Atmospheric Measurement Techniques Vol. 14 ( 10 ) page： 6723 - 6748 2021.10

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Copernicus GmbH

Abstract. Long-term measurements of atmospheric mass concentrationsof black carbon (BC) are needed to investigate changes in its emission,transport, and deposition. However, depending on instrumentation, parametersrelated to BC such as aerosol absorption coefficient (babs) have beenmeasured instead. Most ground-based measurements of babs in the Arctichave been made by filter-based absorption photometers, including particlesoot absorption photometers (PSAPs), continuous light absorption photometers(CLAPs), Aethalometers, and multi-angle absorption photometers (MAAPs). Themeasured babs can be converted to mass concentrations of BC (MBC) byassuming the value of the mass absorption cross section (MAC; MBC= babs/ MAC). However, the accuracy of conversion of babs to MBChas not been adequately assessed. Here, we introduce a systematic method forderiving MAC values from babs measured by these instruments andindependently measured MBC. In this method, MBC was measured with afilter-based absorption photometer with a heated inlet (COSMOS).COSMOS-derived MBC (MBC (COSMOS)) is traceable to a rigorouslycalibrated single particle soot photometer (SP2), and the absolute accuracyof MBC (COSMOS) has been demonstrated previously to be about 15 % inAsia and the Arctic. The necessary conditions for application of this methodare a high correlation of the measured babs with independently measuredMBC and long-term stability of the regression slope, which is denotedas MACcor (MAC derived from the correlation). In general,babs–MBC (COSMOS) correlations were high (r2= 0.76–0.95 forhourly data) at Alert in Canada, Ny-Ålesund in Svalbard, Barrow (NOAA Barrow Observatory) inAlaska, Pallastunturi in Finland, and Fukue in Japan and stable for up to10 years. We successfully estimated MACcor values (10.8–15.1 m2 g−1 at a wavelength of 550 nm for hourly data) for these instruments,and these MACcor values can be used to obtain error-constrainedestimates of MBC from babs measured at these sites even in the past,when COSMOS measurements were not made. Because the absolute values ofMBC at these Arctic sites estimated by this method are consistent witheach other, they are applicable to the study of spatial and temporalvariation in MBC in the Arctic and to evaluation of the performance ofnumerical model calculations.

DOI： 10.5194/amt-14-6723-2021

Absorption instruments inter-comparison campaign at the Arctic Pallas station Reviewed International coauthorship International journal Open Access

Eija Asmi, John Backman, Henri Servomaa, Aki Virkkula, Maria I. Gini, Konstantinos Eleftheriadis, Thomas Müller, Sho Ohata, Yutaka Kondo, Antti Hyvärinen

Atmospheric Measurement Techniques Vol. 14 ( 8 ) page： 5397 - 5413 2021.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Copernicus GmbH

Abstract. Aerosol light absorption was measured during a 1-month field campaign in June–July 2019 at the Pallas Global Atmospheric Watch (GAW) station in northern Finland. Very low aerosol concentrations prevailed during the campaign, which posed a challenge for the instruments' detection capabilities. The campaign provided a real-world test for different absorption measurement techniques supporting the goals of the European Metrology Programme for Innovation and Research (EMPIR) Black Carbon (BC) project in developing aerosol absorption standard and reference methods. In this study we compare the results from five filter-based absorption techniques – aethalometer models AE31 and AE33, a particle soot absorption photometer (PSAP), a multi-angle absorption photometer (MAAP), and a continuous soot monitoring system (COSMOS) – and from one indirect technique called extinction minus scattering (EMS). The ability of the filter-based techniques was shown to be adequate to measure aerosol light absorption coefficients down to around 0.01 Mm−1 levels when data were averaged to 1–2 h. The hourly averaged atmospheric absorption measured by the reference MAAP was 0.09 Mm−1 (at a wavelength of 637 nm). When data were averaged for >1 h, the filter-based methods agreed to around 40 %. COSMOS systematically measured the lowest absorption coefficient values, which was expected due to the sample pre-treatment in the COSMOS inlet. PSAP showed the best linear correlation with MAAP (slope=0.95, R2=0.78), followed by AE31 (slope=0.93). A scattering correction applied to PSAP data improved the data accuracy despite the added noise. However, at very high scattering values the correction led to an underestimation of the absorption. The AE31 data had the highest noise and the correlation with MAAP was the lowest (R2=0.65). Statistically the best linear correlations with MAAP were obtained for AE33 and COSMOS (R2 close to 1), but the biases at around the zero values led to slopes clearly below 1. The sample pre-treatment in the COSMOS instrument resulted in the lowest fitted slope. In contrast to the filter-based techniques, the indirect EMS method was not adequate to measure the low absorption values found at the Pallas site. The lowest absorption at which the EMS signal could be distinguished from the noise was >0.1 Mm−1 at 1–2 h averaging times. The mass absorption cross section (MAC) value measured at a range 0–0.3 Mm−1 was calculated using the MAAP and a single particle soot photometer (SP2), resulting in a MAC value of 16.0±5.7 m2 g−1. Overall, our results demonstrate the challenges encountered in the aerosol absorption measurements in pristine environments and provide some useful guidelines for instrument selection and measurement practices. We highlight the need for a calibrated transfer standard for better inter-comparability of the absorption results.

DOI： 10.5194/amt-14-5397-2021

Seasonal Variation of Wet Deposition of Black Carbon at Ny‐Ålesund, Svalbard Reviewed International coauthorship International journal Open Access

Tatsuhiro Mori, Yutaka Kondo, Sho Ohata, Kumiko Goto‐Azuma, Kaori Fukuda, Yoshimi Ogawa‐Tsukagawa, Nobuhiro Moteki, Atsushi Yoshida, Makoto Koike, P. R. Sinha, Naga Oshima, Hitoshi Matsui, Yutaka Tobo, Masanori Yabuki, Wenche Aas

Journal of Geophysical Research: Atmospheres Vol. 126 ( 12 ) 2021.6

Language：English Publishing type：Research paper (scientific journal) Publisher：American Geophysical Union (AGU)

Black carbon (BC) aerosol deposited in and onto Arctic snow increases the snow's absorption of solar radiation and accelerates snowmelt. Concentrations of BC in the Arctic atmosphere and snow are controlled by wet deposition; however, details of this process are poorly understood owing to the scarcity of time-resolved measurements of BC in hydrometeors. We measured mass concentrations of BC in hydrometeors (C-MBC) and in air (M-BC) with 16% and 15% accuracies, respectively, at Ny-angstrom lesund, Svalbard during 2012-2019. Median monthly M-BC and C-MBC values showed similar seasonal variations, being high in winter-spring and low in summer. Median monthly BC wet deposition mass flux (F-MBC) was highest in winter and lowest in summer, associated with seasonal patterns of C-MBC and precipitation. Seasonally averaged BC size distributions in hydrometeors were similar except for summer. Measurements of M-BC and C-MBC in spring 2017 showed a size-independent removal efficiency, indicating that BC-containing particles were efficiently activated into cloud droplets. These observations at Ny-angstrom lesund were compared with observations at Barrow, Alaska, during 2013-2017. The near-surface M-BC at Ny-angstrom lesund and Barrow had similar seasonal patterns; however, the two sites differed in C-MBC and F-MBC. In summer, C-MBC was low at Ny-angstrom lesund but moderate at Barrow, likely reflecting differences in M-BC in the lower troposphere. Seasonally averaged BC size distributions in hydrometeors were similar at both sites, suggesting that average BC size distributions are similar in the Arctic lower troposphere. The efficiency of BC removal tends to be size-independent during transport, leading to the observed similarity.

DOI： 10.1029/2020JD034110

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2020JD034110

Compositions and mixing states of aerosol particles by aircraft observations in the Arctic springtime, 2018 Reviewed International journal Open Access

Kouji Adachi, Naga Oshima, Sho Ohata, Atsushi Yoshida, Nobuhiro Moteki, Makoto Koike

Atmospheric Chemistry and Physics Vol. 21 ( 5 ) page： 3607 - 3626 2021.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Copernicus GmbH

Abstract. Aerosol particles were collected at various altitudes in
the Arctic during the Polar Airborne Measurements and Arctic Regional
Climate Model Simulation Project 2018 (PAMARCMiP 2018) conducted in the
early spring of 2018. The composition, size, number fraction, and mixing state of
individual aerosol particles were analyzed using transmission electron
microscopy (TEM), and their sources and transport were evaluated by
numerical model simulations. We found that sulfate, sea-salt, mineral-dust,
K-bearing, and carbonaceous particles were the major aerosol constituents.
Many particles were composed of two or more compositions that had coagulated
and were coated with sulfate, organic materials, or both. The number
fraction of mineral-dust and sea-salt particles decreased with increasing
altitude. The K-bearing particles increased within a biomass burning (BB)
plume at altitudes > 3900 m, which originated from Siberia.
Chlorine in sea-salt particles was replaced with sulfate at high altitudes.
These results suggest that the sources, transport, and aging of Arctic
aerosols largely vary depending on the altitude and air-mass history. We also
provide the occurrences of solid-particle inclusions (soot, fly-ash, and
Fe-aggregate particles), some of which are light-absorbing particles. They
were mainly emitted from anthropogenic and biomass burning sources and were
embedded within other relatively large host particles. Our TEM measurements
revealed the detailed mixing state of individual particles at various
altitudes in the Arctic. This information facilitates the accurate
evaluation of the aerosol influences on Arctic haze, radiation balance,
cloud formation, and snow/ice albedo when deposited.

DOI： 10.5194/acp-21-3607-2021

Studies on Arctic aerosols and clouds during the ArCS project Reviewed International journal Open Access

M. Koike, K. Goto-Azuma, Y. Kondo, H. Matsui, T. Mori, N. Moteki, S. Ohata, H. Okamoto, N. Oshima, K. Sato, T. Takano, Y. Tobo, J. Ukita, A. Yoshida

Polar Science Vol. 27 page： 100621 - 100621 2021.3

Seasonal Variation of Wet Deposition of Black Carbon in Arctic Alaska Reviewed International coauthorship

T. Mori, Y. Kondo, S. Ohata, Y. Zhao, P. R. Sinha, N. Oshima, H. Matsui, N. Moteki, M. Koike

Journal of Geophysical Research: Atmospheres Vol. 125 ( 16 ) 2020.8

Abundances and Microphysical Properties of Light‐Absorbing Iron Oxide and Black Carbon Aerosols Over East Asia and the Arctic Reviewed Open Access

Atsushi Yoshida, Nobuhiro Moteki, Sho Ohata, Tatsuhiro Mori, Makoto Koike, Yutaka Kondo, Hitoshi Matsui, Naga Oshima, Akinori Takami, Kazuyuki Kita

Journal of Geophysical Research: Atmospheres Vol. 125 ( 15 ) 2020.8

Language：English Publishing type：Research paper (scientific journal) Publisher：American Geophysical Union (AGU)

Black carbon (BC), brown carbon, and light-absorbing iron oxides (FeOx) aerosols affect Earth's energy budget through their strong absorption of solar radiation. FeOx aerosols can also affect global biogeochemical cycles through their role as a nutrient for oceanic phytoplankton. However, observational data for these aerosols required for evaluating their effects using global models are scarce, especially for FeOx. Here, we summarize and compare the data sets of BC and FeOx from five ground-based and three aircraft observation campaigns conducted in the East Asian and Arctic regions during the 2009-2018 period acquired using a modified single-particle soot photometer. In these campaigns, >80% of FeOx-containing aerosols in the 170-270 nm FeOx core size range had microphysical features indicating an anthropogenic origin. The particle size distribution for each of the BC and FeOx was similar in all of the data sets except for those dominated by fresh urban pollution or pristine Arctic air. The campaign-averaged mass concentrations of FeOx and BC were similar to 60-360 ng/m(3) and similar to 240-1,300 ng/m(3), respectively, in East Asia, and similar to 6 ng/m(3) and similar to 20-30 ng/m(3), respectively, in the Arctic. The campaign-averaged FeOx/BC mass concentration ratio varied within a narrow range of 0.2-0.6 in both East Asian and Arctic regions. In every campaign, FeOx, BC, and carbon monoxide were tightly correlated with each other with similar slope to the urban campaigns (around Tokyo), implying the spatiotemporal variation of anthropogenic FeOx emission around northern middle-to-high latitudes is similar to those of anthropogenic BC and CO emissions.

DOI： 10.1029/2019JD032301

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2019JD032301

Changes in black carbon and PM<sub>2.5</sub> in Tokyo in 2003-2017. Reviewed Open Access

Mori T, Ohata S, Morino Y, Koike M, Moteki N, Kondo Y

Proceedings of the Japan Academy. Series B, Physical and biological sciences Vol. 96 ( 3 ) page： 122-129 2020.3

Concentrations and size distributions of black carbon in the surface snow of Eastern Antarctica in 2011 Reviewed Open Access

T. Kinase, K. Adachi, N. Oshima, K. Goto-Azuma, Y. Ogawa-Tsukagawa, M. Shiobara, Y. Kondo, N. Moteki, S. Ohata, T. Mori, M. Hayashi, K. Hara, H. Kawashima, and K. Kita

Journal of Geophysical Research: Atmospheres Vol. 125 2019.12

Black Carbon and Inorganic Aerosols in Arctic Snowpack Reviewed Open Access

Mori Tatsuhiro, Goto-Azuma Kumiko, Kondo Yutaka, Ogawa-Tsukagawa Yoshimi, Miura Kazuhiko, Hirabayashi Motohiro, Oshima Naga, Koike Makoto, Kupiainen Kaarle, Moteki Nobuhiro, Ohata Sho, Sinha P. R., Sugiura Konosuke, Aoki Teruo, Schneebeli Martin, Steffen Konrad, Sato Atsushi, Tsushima Akane, Makarov Vladimir, Omiya Satoshi, Sugimoto Atsuko, Takano Shinya, Nagatsuka Naoko

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES Vol. 124 ( 23 ) page： 13325-13356 2019.12

Accuracy of black carbon measurements by a filter-based absorption photometer with a heated inlet Reviewed International coauthorship International journal

Sho Ohata, Yutaka Kondo, Nobuhiro Moteki, Tatsuhiro Mori, Atsushi Yoshida, Puna R. Sinha, Makoto Koike

AEROSOL SCI TECH Vol. 53 ( 9 ) page： 1079 - 1091 2019.9

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS INC

Long-term measurements of black carbon (BC) aerosols by filter-based absorption photometers with a heated inlet (COSMOS) in different regions have been useful in elucidating spatial variations and radiative impacts of BC. Evaluations of mass concentrations of BC (M-BC) measured by the COSMOS have been made by our previous studies through comparisons with other measurement techniques. However, how variations in the microphysical properties of BC and the co-existing light scattering aerosols affect the COSMOS measurements should be evaluated in more detail. In this study, we assessed these potential effects under various field environments in the Arctic and in the East Asia. From the slopes of the correlation plots between the M-BC values measured by the COSMOS and a single-particle soot photometer, the average accuracy of the COSMOS was estimated as similar to 10% in the M-BC range 1-3000 ng m(-3). On an hourly basis, the estimated sensitivity of the COSMOS M-BC values to the changes in the BC size distributions was less than 10%, within the typical variabilities of BC size at individual observation sites. The COSMOS measurements depended little on the mixing states of BC and the concentrations of co-existing light scattering aerosols, except in the maritime air masses of East Asia, where the relative abundance of sea salt to BC was very high. The M-BC measured by COSMOS also well agreed with elemental carbon measurements. Our results demonstrate the high reliability of COSMOS measurements under various environments. Copyright (c) 2019 American Association for Aerosol Research

DOI： 10.1080/02786826.2019.1627283