Articles | Volume 25, issue 3
https://doi.org/10.5194/acp-25-1965-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-25-1965-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
14 Feb 2025
Research article |
| 14 Feb 2025
| 14 Feb 2025
Diurnal, seasonal, and interannual variations in δ(18O) of atmospheric O2 and its application to evaluate natural and anthropogenic changes in oxygen, carbon, and water cycles
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8569, Japan
Satoshi Sugawara
Miyagi University of Education, Sendai 980-0845, Japan
Atsushi Okazaki
Chiba University, Chiba 263-8522, Japan
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The JapanFlux2024 dataset, created through collaboration across Japan and East Asia, includes eddy covariance data from 83 sites spanning 683 site-years (1990–2023). This comprehensive dataset offers valuable insights into energy, water, and CO2 fluxes, supporting research on land–atmosphere interactions and process models; fosters global collaboration; and advances research in environmental science and regional climate dynamics.
Satoshi Sugawara, Ikumi Oyabu, Kenji Kawamura, Shigeyuki Ishidoya, Shinji Morimoto, Shuji Aoki, Takakiyo Nakazawa, Sakae Toyoda, and Hideyuki Honda
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This preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
Short summary
Short summary
Stratospheric air samples have been collected using balloon-borne cryogenic samplers over Japan and analyzed for the isotopic and elemental ratios of noble gases. We report the results of the first study on the vertical changes of Kr, Xe, and Ne in the stratosphere. The observed results suggest that not only gravitational separation but also kinetic fractionation occurred in the stratosphere. The kinetic fractionations would be an additional tool to diagnose stratospheric transport processes.
Nobuyuki Aoki and Shigeyuki Ishidoya
EGUsphere, https://doi.org/10.5194/egusphere-2025-2618, https://doi.org/10.5194/egusphere-2025-2618, 2025
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In this study, offsets of CO2 values due to thermal diffusion effect were observed in the outflowing gas from cylinders finding that the CO2 mole fraction in a cylinder deviate by this effect as the pressure dropped. This result suggests that the deviation in the CO2 value in the cylinder is caused not only by the adsorption and desorption effects but also by the thermal diffusion fractionation effect.
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EGUsphere, https://doi.org/10.5194/egusphere-2025-1003, https://doi.org/10.5194/egusphere-2025-1003, 2025
Short summary
Short summary
We have been collected stratospheric air samples since 1985 over Japan and analyzed them for δ13CO2. δ13CO2 has decreased through time in the mid-stratosphere with an average rate of change of −0.026 ± 0.001 ‰ yr−1. It has become clear that the oxidation of methane and gravitational separation are important for stratospheric δ13CO2 variations. We newly defined ‘stratospheric potential δ13C’ as a quasi-conservative parameter and demonstrated that it can be used as an air age tracer.
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A method evaluating techniques for carbon neutrality, such as carbon capture and storage (CCS), is important. This study presents a method to evaluate CO2 emissions from a cement plant based on atmospheric O2 and CO2 measurements. The method will also be useful for evaluating CO2 capture from flue gas at CCS plants, since the plants remove CO2 from the atmosphere without causing any O2 changes, just as cement plants do, differing only in the direction of CO2 exchange with the atmosphere.
Kazuki Kamezaki, Sebastian O. Danielache, Shigeyuki Ishidoya, Takahisa Maeda, and Shohei Murayama
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2023-209, https://doi.org/10.5194/amt-2023-209, 2023
Revised manuscript not accepted
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Recently, MIRA Pico, a portable continuous carbonyl sulfide (COS) concentration analyzer using mid-infrared absorption, has been released. MIRA Pico has a lower cost and is smaller than conventional laser COS analyzers. However, actual COS atmospheric measurement results using MIRA Pico have not yet been reported. In this study, we modified and tested the MIRA Pico for atmospheric COS concentration measurements. We used the modified MIRA Pico for observations at Tsukuba, Japan.
Nobuyuki Aoki, Shigeyuki Ishidoya, Shohei Murayama, and Nobuhiro Matsumoto
Atmos. Meas. Tech., 15, 5969–5983, https://doi.org/10.5194/amt-15-5969-2022, https://doi.org/10.5194/amt-15-5969-2022, 2022
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The CO2 concentration in a cylinder is affected by carbon dioxide (CO2) adsorption to a cylinder’s internal surface and fractionation of CO2 and air in the preparation of standard mixtures. We demonstrate that the effects make the CO2 molar fractions deviate in standard mixtures prepared by diluting pure CO2 with air three times. This means that CO2 standard gases are difficult to gravimetrically prepare through multistep dilution.
Shigeyuki Ishidoya, Kazuhiro Tsuboi, Yosuke Niwa, Hidekazu Matsueda, Shohei Murayama, Kentaro Ishijima, and Kazuyuki Saito
Atmos. Chem. Phys., 22, 6953–6970, https://doi.org/10.5194/acp-22-6953-2022, https://doi.org/10.5194/acp-22-6953-2022, 2022
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The atmospheric O2 / N2 ratio and CO2 concentration over the western North Pacific are presented. We found significant modification of the seasonal APO cycle in the middle troposphere due to the interhemispheric mixing of air. APO driven by the net marine biological activities indicated annual sea–air O2 flux during El Niño. Terrestrial biospheric and oceanic CO2 uptakes during 2012–2019 were estimated to be 1.8 and 2.8 Pg C a−1, respectively.
Nobuyuki Aoki, Shigeyuki Ishidoya, Yasunori Tohjima, Shinji Morimoto, Ralph F. Keeling, Adam Cox, Shuichiro Takebayashi, and Shohei Murayama
Atmos. Meas. Tech., 14, 6181–6193, https://doi.org/10.5194/amt-14-6181-2021, https://doi.org/10.5194/amt-14-6181-2021, 2021
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Observing the minimal long-term change in atmospheric O2 molar fraction combined with CO2 observation enables us to estimate terrestrial biospheric and oceanic CO2 uptakes separately. In this study, we firstly identified the span offset between the laboratory O2 scales using our developed high-precision standard mixtures, suggesting that the result may allow us to estimate terrestrial biospheric and oceanic CO2 uptakes precisely.
Shigeyuki Ishidoya, Satoshi Sugawara, Yasunori Tohjima, Daisuke Goto, Kentaro Ishijima, Yosuke Niwa, Nobuyuki Aoki, and Shohei Murayama
Atmos. Chem. Phys., 21, 1357–1373, https://doi.org/10.5194/acp-21-1357-2021, https://doi.org/10.5194/acp-21-1357-2021, 2021
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The surface Ar / N2 ratio showed not only secular increasing trends, but also interannual variations in phase with the global ocean heat content (OHC). Sensitivity test by using a two-dimensional model indicated that the secular trend in the Ar / N2 ratio is modified by the gravitational separation in the stratosphere. The analytical results imply that the surface Ar/N2 ratio is an important tracer for detecting spatiotemporally integrated changes in OHC and stratospheric circulation.
Ikumi Oyabu, Kenji Kawamura, Kyotaro Kitamura, Remi Dallmayr, Akihiro Kitamura, Chikako Sawada, Jeffrey P. Severinghaus, Ross Beaudette, Anaïs Orsi, Satoshi Sugawara, Shigeyuki Ishidoya, Dorthe Dahl-Jensen, Kumiko Goto-Azuma, Shuji Aoki, and Takakiyo Nakazawa
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Air in polar ice cores provides information on past atmosphere and climate. We present a new method for simultaneously measuring eight gases (CH4, N2O and CO2 concentrations; isotopic ratios of N2 and O2; elemental ratios between N2, O2 and Ar; and total air content) from single ice-core samples with high precision.
Masahito Ueyama, Yuta Takao, Hiromi Yazawa, Makiko Tanaka, Hironori Yabuki, Tomo'omi Kumagai, Hiroki Iwata, Md. Abdul Awal, Mingyuan Du, Yoshinobu Harazono, Yoshiaki Hata, Takashi Hirano, Tsutom Hiura, Reiko Ide, Sachinobu Ishida, Mamoru Ishikawa, Kenzo Kitamura, Yuji Kominami, Shujiro Komiya, Ayumi Kotani, Yuta Inoue, Takashi Machimura, Kazuho Matsumoto, Yojiro Matsuura, Yasuko Mizoguchi, Shohei Murayama, Hirohiko Nagano, Taro Nakai, Tatsuro Nakaji, Ko Nakaya, Shinjiro Ohkubo, Takeshi Ohta, Keisuke Ono, Taku M. Saitoh, Ayaka Sakabe, Takanori Shimizu, Seiji Shimoda, Michiaki Sugita, Kentaro Takagi, Yoshiyuki Takahashi, Naoya Takamura, Satoru Takanashi, Takahiro Takimoto, Yukio Yasuda, Qinxue Wang, Jun Asanuma, Hideo Hasegawa, Tetsuya Hiyama, Yoshihiro Iijima, Shigeyuki Ishidoya, Masayuki Itoh, Tomomichi Kato, Hiroaki Kondo, Yoshiko Kosugi, Tomonori Kume, Takahisa Maeda, Shoji Matsuura, Trofim Maximov, Takafumi Miyama, Ryo Moriwaki, Hiroyuki Muraoka, Roman Petrov, Jun Suzuki, Shingo Taniguchi, and Kazuhito Ichii
Earth Syst. Sci. Data, 17, 3807–3833, https://doi.org/10.5194/essd-17-3807-2025, https://doi.org/10.5194/essd-17-3807-2025, 2025
Short summary
Short summary
The JapanFlux2024 dataset, created through collaboration across Japan and East Asia, includes eddy covariance data from 83 sites spanning 683 site-years (1990–2023). This comprehensive dataset offers valuable insights into energy, water, and CO2 fluxes, supporting research on land–atmosphere interactions and process models; fosters global collaboration; and advances research in environmental science and regional climate dynamics.
Satoshi Sugawara, Ikumi Oyabu, Kenji Kawamura, Shigeyuki Ishidoya, Shinji Morimoto, Shuji Aoki, Takakiyo Nakazawa, Sakae Toyoda, and Hideyuki Honda
EGUsphere, https://doi.org/10.5194/egusphere-2025-2916, https://doi.org/10.5194/egusphere-2025-2916, 2025
This preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
Short summary
Short summary
Stratospheric air samples have been collected using balloon-borne cryogenic samplers over Japan and analyzed for the isotopic and elemental ratios of noble gases. We report the results of the first study on the vertical changes of Kr, Xe, and Ne in the stratosphere. The observed results suggest that not only gravitational separation but also kinetic fractionation occurred in the stratosphere. The kinetic fractionations would be an additional tool to diagnose stratospheric transport processes.
Nobuyuki Aoki and Shigeyuki Ishidoya
EGUsphere, https://doi.org/10.5194/egusphere-2025-2618, https://doi.org/10.5194/egusphere-2025-2618, 2025
Short summary
Short summary
In this study, offsets of CO2 values due to thermal diffusion effect were observed in the outflowing gas from cylinders finding that the CO2 mole fraction in a cylinder deviate by this effect as the pressure dropped. This result suggests that the deviation in the CO2 value in the cylinder is caused not only by the adsorption and desorption effects but also by the thermal diffusion fractionation effect.
Fumitoshi Kawasaki, Atsushi Okazaki, Kenta Kurosawa, Tadashi Tsuyuki, and Shunji Kotsuki
EGUsphere, https://doi.org/10.5194/egusphere-2025-1785, https://doi.org/10.5194/egusphere-2025-1785, 2025
Short summary
Short summary
A major challenge in weather control aimed at mitigating extreme weather events is identifying effective control inputs under limited computational resources. This study proposes a novel control framework called model predictive control with foreseeing horizon, designed to efficiently control chaotic dynamical systems. Using a 40-variable chaotic dynamical model, the proposed method successfully mitigated extreme events and reduced computational cost compared to the conventional approach.
Atsushi Okazaki, Diego Carrio, Quentin Dalaiden, Jarrah Harrison-Lofthouse, Shunji Kotsuki, and Kei Yoshimura
EGUsphere, https://doi.org/10.5194/egusphere-2025-1389, https://doi.org/10.5194/egusphere-2025-1389, 2025
Short summary
Short summary
Data assimilation (DA) has been used to reconstruct paleoclimate fields. DA integrates model simulations and climate proxies based on their error sizes. Consequently, error information is vital for DA to function optimally. This study estimated observation errors using "innovation statistics" and demonstrated DA with estimated errors outperformed previous studies.
Satoshi Sugawara, Shinji Morimoto, Shigeyuki Ishidoya, Taku Umezawa, Shuji Aoki, Takakiyo Nakazawa, Sakae Toyoda, Kentaro Ishijima, Daisuke Goto, and Hideyuki Honda
EGUsphere, https://doi.org/10.5194/egusphere-2025-1003, https://doi.org/10.5194/egusphere-2025-1003, 2025
Short summary
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We have been collected stratospheric air samples since 1985 over Japan and analyzed them for δ13CO2. δ13CO2 has decreased through time in the mid-stratosphere with an average rate of change of −0.026 ± 0.001 ‰ yr−1. It has become clear that the oxidation of methane and gravitational separation are important for stratospheric δ13CO2 variations. We newly defined ‘stratospheric potential δ13C’ as a quasi-conservative parameter and demonstrated that it can be used as an air age tracer.
Takahito Mitsui, Shunji Kotsuki, Naoya Fujiwara, Atsushi Okazaki, and Keita Tokuda
EGUsphere, https://doi.org/10.5194/egusphere-2025-987, https://doi.org/10.5194/egusphere-2025-987, 2025
Short summary
Short summary
Extreme weather poses serious risks, making prevention crucial. Using the Lorenz 96 model as a testbed, we propose a bottom-up approach to mitigate extreme events via local interventions guided by multi-scenario ensemble forecasts. Unlike control-theoretic methods, our approach selects the best control scenario from available options. Achieving up to 99.4 % success, it outperforms previous methods while keeping costs reasonable, offering a practical way to reduce disasters with limited control.
Kenta Kurosawa, Atsushi Okazaki, Fumitoshi Kawasaki, and Shunji Kotsuki
EGUsphere, https://doi.org/10.5194/egusphere-2025-595, https://doi.org/10.5194/egusphere-2025-595, 2025
Short summary
Short summary
We propose Ensemble Model Predictive Control (EnMPC), a novel method that improves control of complex systems like weather by integrating control theory with data assimilation. Unlike traditional methods, which are computationally expensive, EnMPC uses ensemble simulations to efficiently handle uncertainties and optimize solutions. This approach reduces computational cost while maintaining accuracy, making it a promising step toward real-world applications in dynamic system control.
Shunji Kotsuki, Kenta Shiraishi, and Atsushi Okazaki
EGUsphere, https://doi.org/10.48550/arXiv.2407.17781, https://doi.org/10.48550/arXiv.2407.17781, 2024
Short summary
Short summary
Artificial intelligence (AI) is playing a bigger role in weather forecasting, often competing with physical models. However, combining AI models with data assimilation, a process that improves weather forecasts by incorporating observation data, is still relatively unexplored. This study explored coupling ensemble data assimilation with an AI weather prediction model ClimaX, succeeded in employing weather forecasts stably by applying techniques conventionally used for physical models.
Toshiyuki Ohtsuka, Atsushi Okazaki, Masaki Ogura, and Shunji Kotsuki
EGUsphere, https://doi.org/10.48550/arXiv.2405.19546, https://doi.org/10.48550/arXiv.2405.19546, 2024
Preprint withdrawn
Short summary
Short summary
We utilize weather forecasts in the reverse direction and determine how much we should change the temperature or humidity of the atmosphere at a certain time to change the future rainfall as desired. Even though a weather phenomenon is complicated, we can superimpose the effects of small changes in the atmosphere and find suitable small changes to realize desirable rainfall by solving an optimization problem. We examine this idea on a realistic weather simulator and show it is promising.
Shigeyuki Ishidoya, Kazuhiro Tsuboi, Hiroaki Kondo, Kentaro Ishijima, Nobuyuki Aoki, Hidekazu Matsueda, and Kazuyuki Saito
Atmos. Chem. Phys., 24, 1059–1077, https://doi.org/10.5194/acp-24-1059-2024, https://doi.org/10.5194/acp-24-1059-2024, 2024
Short summary
Short summary
A method evaluating techniques for carbon neutrality, such as carbon capture and storage (CCS), is important. This study presents a method to evaluate CO2 emissions from a cement plant based on atmospheric O2 and CO2 measurements. The method will also be useful for evaluating CO2 capture from flue gas at CCS plants, since the plants remove CO2 from the atmosphere without causing any O2 changes, just as cement plants do, differing only in the direction of CO2 exchange with the atmosphere.
Kazuki Kamezaki, Sebastian O. Danielache, Shigeyuki Ishidoya, Takahisa Maeda, and Shohei Murayama
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2023-209, https://doi.org/10.5194/amt-2023-209, 2023
Revised manuscript not accepted
Short summary
Short summary
Recently, MIRA Pico, a portable continuous carbonyl sulfide (COS) concentration analyzer using mid-infrared absorption, has been released. MIRA Pico has a lower cost and is smaller than conventional laser COS analyzers. However, actual COS atmospheric measurement results using MIRA Pico have not yet been reported. In this study, we modified and tested the MIRA Pico for atmospheric COS concentration measurements. We used the modified MIRA Pico for observations at Tsukuba, Japan.
Nobuyuki Aoki, Shigeyuki Ishidoya, Shohei Murayama, and Nobuhiro Matsumoto
Atmos. Meas. Tech., 15, 5969–5983, https://doi.org/10.5194/amt-15-5969-2022, https://doi.org/10.5194/amt-15-5969-2022, 2022
Short summary
Short summary
The CO2 concentration in a cylinder is affected by carbon dioxide (CO2) adsorption to a cylinder’s internal surface and fractionation of CO2 and air in the preparation of standard mixtures. We demonstrate that the effects make the CO2 molar fractions deviate in standard mixtures prepared by diluting pure CO2 with air three times. This means that CO2 standard gases are difficult to gravimetrically prepare through multistep dilution.
Shigeyuki Ishidoya, Kazuhiro Tsuboi, Yosuke Niwa, Hidekazu Matsueda, Shohei Murayama, Kentaro Ishijima, and Kazuyuki Saito
Atmos. Chem. Phys., 22, 6953–6970, https://doi.org/10.5194/acp-22-6953-2022, https://doi.org/10.5194/acp-22-6953-2022, 2022
Short summary
Short summary
The atmospheric O2 / N2 ratio and CO2 concentration over the western North Pacific are presented. We found significant modification of the seasonal APO cycle in the middle troposphere due to the interhemispheric mixing of air. APO driven by the net marine biological activities indicated annual sea–air O2 flux during El Niño. Terrestrial biospheric and oceanic CO2 uptakes during 2012–2019 were estimated to be 1.8 and 2.8 Pg C a−1, respectively.
Taku Umezawa, Satoshi Sugawara, Kenji Kawamura, Ikumi Oyabu, Stephen J. Andrews, Takuya Saito, Shuji Aoki, and Takakiyo Nakazawa
Atmos. Chem. Phys., 22, 6899–6917, https://doi.org/10.5194/acp-22-6899-2022, https://doi.org/10.5194/acp-22-6899-2022, 2022
Short summary
Short summary
Greenhouse gas methane in the Arctic atmosphere has not been accurately reported for 1900–1980 from either direct observations or ice core reconstructions. By using trace gas data from firn (compacted snow layers above ice sheet), air samples at two Greenland sites, and a firn air transport model, this study suggests a likely range of the Arctic methane reconstruction for the 20th century. Atmospheric scenarios from two previous studies are also evaluated for consistency with the firn data sets.
Nobuyuki Aoki, Shigeyuki Ishidoya, Yasunori Tohjima, Shinji Morimoto, Ralph F. Keeling, Adam Cox, Shuichiro Takebayashi, and Shohei Murayama
Atmos. Meas. Tech., 14, 6181–6193, https://doi.org/10.5194/amt-14-6181-2021, https://doi.org/10.5194/amt-14-6181-2021, 2021
Short summary
Short summary
Observing the minimal long-term change in atmospheric O2 molar fraction combined with CO2 observation enables us to estimate terrestrial biospheric and oceanic CO2 uptakes separately. In this study, we firstly identified the span offset between the laboratory O2 scales using our developed high-precision standard mixtures, suggesting that the result may allow us to estimate terrestrial biospheric and oceanic CO2 uptakes precisely.
Shigeyuki Ishidoya, Satoshi Sugawara, Yasunori Tohjima, Daisuke Goto, Kentaro Ishijima, Yosuke Niwa, Nobuyuki Aoki, and Shohei Murayama
Atmos. Chem. Phys., 21, 1357–1373, https://doi.org/10.5194/acp-21-1357-2021, https://doi.org/10.5194/acp-21-1357-2021, 2021
Short summary
Short summary
The surface Ar / N2 ratio showed not only secular increasing trends, but also interannual variations in phase with the global ocean heat content (OHC). Sensitivity test by using a two-dimensional model indicated that the secular trend in the Ar / N2 ratio is modified by the gravitational separation in the stratosphere. The analytical results imply that the surface Ar/N2 ratio is an important tracer for detecting spatiotemporally integrated changes in OHC and stratospheric circulation.
Ikumi Oyabu, Kenji Kawamura, Kyotaro Kitamura, Remi Dallmayr, Akihiro Kitamura, Chikako Sawada, Jeffrey P. Severinghaus, Ross Beaudette, Anaïs Orsi, Satoshi Sugawara, Shigeyuki Ishidoya, Dorthe Dahl-Jensen, Kumiko Goto-Azuma, Shuji Aoki, and Takakiyo Nakazawa
Atmos. Meas. Tech., 13, 6703–6731, https://doi.org/10.5194/amt-13-6703-2020, https://doi.org/10.5194/amt-13-6703-2020, 2020
Short summary
Short summary
Air in polar ice cores provides information on past atmosphere and climate. We present a new method for simultaneously measuring eight gases (CH4, N2O and CO2 concentrations; isotopic ratios of N2 and O2; elemental ratios between N2, O2 and Ar; and total air content) from single ice-core samples with high precision.
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Short summary
The 18O/16O ratio of atmospheric oxygen, δatm(18O), is higher than that of ocean water due to isotopic effects during biospheric activities. This is known as the Dole–Morita effect, and its millennial-scale variations are recorded in ice cores. However, small variations of δatm(18O) in the present day have never been detected so far. This paper presents the first observations of diurnal, seasonal, and secular variations in δatm(18O) and applies them to evaluate oxygen, carbon, and water cycles.
The 18O/16O ratio of atmospheric oxygen, δatm(18O), is higher than that of ocean water due to...
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