Takashi SEKIYA

Profile

Takashi SEKIYA

Research Institute for Global Change
Earth Surface System Research Center
Environmental Geochemical Cycle Research Group
Researcher

Address

Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
Yokohama Institute for Earth Sciences (YES)
3173-25, Showa-machi, Kanazawa-ku, Yokohama, Kanagawa
Tel: +81-(0)45-778-5719
Fax: +81-(0)45-778-5706


Research Interests

  • Data assimilation for atmospheric chemistry and aerosols
  • Short- and long-term changes in short-lived atmospheric constituents
  • Developments and applications of global chemical transport model

Curriculum Vitae

Education experience

Apr. 2011-Mar. 2014 Ph.D., Nagoya University, Department of Earth and Environmental Sciences, Graduate School of Environmental Studies
Apr. 2009-Mar. 2011 M.Sc., Nagoya University, Department of Earth and Environmental Sciences, Graduate School of Environmental Studies
Apr. 2005-Mar. 2009 B.Sc., Nagoya University, Department of Science

Research experience

Oct. 2025- Researcher, ESS, RIGC, JAMSTEC
Aug. 2019-Sep. 2025 Researcher(II), ESS, RIGC, JAMSTEC
Apr. 2019-Jul. 2019 Post-doc researcher, IACE, RIGC, JAMSTEC
Apr. 2016-Mar. 2019 Post-doc researcher, Project Team for HPC Advanced Predictions utilizing Big Data, JAMSTEC
Apr. 2014-Mar. 2016 Post-doc Researcher, Nagoya University

Publications

  • 39) Quaglia, I., Visioni, D., Bednarz, E. M., Zhu, Y., Stenchikov, G., Aquila, V., Liu, C.-C., Mann, G. W., Peng, Y., Sekiya, T., Tilmes, S., Wang, X., Watanabe, S., Yu, P., Zhang, J., Yu, W., and Zhuo, Z.: Multi-model analysis of the impact of water vapor on the radiative forcing of volcanic aerosols after the 2022 Hunga Eruption, Atmos. Chem. Phys., 26, 7677–7704, https://doi.org/10.5194/acp-26-7677-2026, 2026.
  • 38) Lee, W. R., Visioni, D., Wagman, B. M., Wentland, C. R., Kravitz, B., Watanabe, S., Sekiya, T., Jones, A., Haywood, J., Henry, M., and Bednarz, E. M.: G6-1.5K-SAI and G6sulfur: changes in impacts and uncertainty depending on stratospheric aerosol injection strategy in the Geoengineering Model Intercomparison Project, Atmos. Chem. Phys., 26, 7463–7483, https://doi.org/10.5194/acp-26-7463-2026, 2026.
  • 37) Guan, X., Sato, T. O., Sekiya, T., Kuroda, T., Yang, H., and Kasai, Y.: Quantitative analysis of global air cleanliness using the Clean aIr Index (CII), Atmos. Environ., 374, 121930, https://doi.org/10.1016/j.atmosenv.2026.121930, 2026.
  • 36) Jones, D. B. A., Prates, L., Qu, Z., Cheng, W. Y. Y., Miyazaki, K., Sekiya, T., Inness, A., Kumar, R., Tang, X., Worden, H., Koren, G., and Huijnen, V.: Assessment of regional and interannual variations in tropospheric ozone in chemical reanalyses, Atmos. Chem. Phys., 26, 6655–6682, https://doi.org/10.5194/acp-26-6655-2026, 2026.
  • 35) Taketani, F., Matsumoto, K., Sekiya, T., Yamaji, K., and Kanaya, Y.: An observational case study for inorganic nitrogen dry deposition potential on sea-surface primary production in the subtropical, western North Pacific, Sci. Rep., 16, 9068, https://doi.org/10.1038/s41598-026-39401-x, 2026.
  • 34) Takashima, H., Kanaya, Y., Iwamoto, Y., Takeda, K., Sekiya, T., Taketani, F., Friedrich, M. M., Van Roozendael, M., Ooki, A., Miyakawa, T., Ogino S.-Y., and Katsumata, M.: Simultaneous observations of atmospheric IO radical, O3, and sea surface iodide over the tropical western Pacific warm pool: strong correlation of IO levels with estimated inorganic iodine fluxes, Prog. Earth Planet. Sci., 12, 104, https://doi.org/10.1186/s40645-025-00775-7, 2025.
  • 33) Ha, P. T. M., Kanaya, Y., Yamaji, K., Itahashi, S., Chatani, S., Sekiya, T., Hernández, M. D. A., Burrows, J. P., Schlager, H., Lichtenstern, M., Poehlker, M., and Holanda, B.: Assessing BC and CO emissions from China using EMeRGe aircraft observations and WRF/CMAQ modelling, Atmos. Chem. Phys., 25, 13429–13452, https://doi.org/10.5194/acp-25-13429-2025, 2025.
  • 32) Zhuo, Z., Wang, X., Zhu, Y., Yu, W., Bednarz, E. M., Fleming, E., Colarco, P. R., Watanabe, S., Plummer, D., Stenchikov, G., Randel, W., Bourassa, A., Aquila, V., Sekiya, T., Schoeberl, M. R., Tilmes, S., Zhang, J., Kushner, P. J., and Pausata, F. S. R.: Comparing multi-model ensemble simulations with observations and decadal projections of upper atmospheric variations following the Hunga eruption, Atmos. Chem. Phys., 25, 13161–13176, https://doi.org/10.5194/acp-25-13161-2025, 2025.
  • 31) Zhu, Y., Akiyoshi, H., Aquila, V., Asher, E., Bednarz, E. M., Bekki, S., Brühl, C., Butler, A. H., Case, P., Chabrillat, S., Chiodo, G., Clyne, M., Colarco, P. R., Dhomse, S., Falletti, L., Fleming, E., Johnson, B., Jörimann, A., Kovilakam, M., Koren, G., Kuchar, A., Lebas, N., Liang, Q., Liu, C.-C., Mann, G., Manyin, M., Marchand, M., Morgenstern, O., Newman, P., Oman, L. D., Østerstrøm, F. F., Peng, Y., Plummer, D., Quaglia, I., Randel, W., Rémy, S., Sekiya, T., Steenrod, S., Sukhodolov, T., Tilmes, S., Tsigaridis, K., Ueyama, R., Visioni, D., Wang, X., Watanabe, S., Yamashita, Y., Yu, P., Yu, W., Zhang, J., and Zhuo, Z.: Hunga Tonga–Hunga Ha′apai Volcano Impact Model Observation Comparison (HTHH-MOC) project: experiment protocol and model descriptions, Geosci. Model Dev., 18, 5487–5512, https://doi.org/10.5194/gmd-18-5487-2025, 2025.
  • 30) Sekiya, T., Takashima, H., Kanaya, Y., Taketani, F., Sudo, K., Friedrich, M. M., and Van Roozendael, M.: Evaluation of processes driving iodine monoxide and ozone variability over the Western Pacific warm pool, Prog. Earth Planet. Sci., 12, 44, https://doi.org/10.1186/s40645-025-00712-8, 2025
  • 29) Sekiya, T., Emili, E., Miyazaki, K., Inness, A., Qu, Z., Pierce, R. B., Jones, D., Worden, H., Cheng, W. Y. Y., Huijnen, V., and Koren, G.: Assessing the relative impacts of satellite ozone and its precursor observations to improve global tropospheric ozone analysis using multiple chemical reanalysis systems, Atmos. Chem. Phys., 25, 2243–2268, https://doi.org/10.5194/acp-25-2243-2025, 2025.
  • 28) Rijsdijk, P., Eskes, H., Dingemans, A., Boersma, K. F., Sekiya, T., Miyazaki, K., and Houweling, S.: Quantifying uncertainties in satellite NO2 superobservations for data assimilation and model evaluation, Geosci. Model Dev., 18, 483–509, https://doi.org/10.5194/gmd-18-483-2025, 2025.
  • 27) Tanimoto, H., Matsunaga, T., Someya, Y., Fujinawa, T., Ohyama, H., Morino, I., Yashiro, H., Sugita, T., Inomata, S., Müller, A., Saeki, T., Yoshida, Y., Niwa, Y., Saito, M., Noda, H., Yamashita, Y., Ikeda, K., Saigusa, N., Machida, T., Frey, M. M., Lim, H., Srivastava, P., Jin, Y., Shimizu, A., Nishizawa, T., Kanaya, Y., Sekiya, T., Patra, P., Takigawa, M., Bisht. J., Kasai, Y., and Sato, T. O., The greenhouse gas observation mission with Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW): objectives, conceptual framework and scientific contributions. Prog Earth Planet Sci 12, 8, https://doi.org/10.1186/s40645-025-00684-9, 2025.
  • 26) 山口 将大, 金谷 有剛, 滝川 雅之, Jagat S. H. Bisht, 関谷 高志, Prabir K. Patra, 杉田 考史, 谷本 浩志, 擬似衛星観測データを用いた発散法によるCO2およびNOXの地表排出フラックス推計, 日本リモートセンシング学会誌, 44 (2), 156-165, https://doi.org/10.11440/rssj.2024.007, 2024（査読無）.
  • 25) 藤縄 環, 林 顯光, 佐藤 知紘, 関谷 高志, 山下 陽介, 中村 綾乃, 杉田 考史, 金谷 有剛, 笠井 康子, 谷本 浩志, GOSAT-GW TANSO-3 L2 NO2プロダクト（T3L2NO2）の導出アルゴリズム, 日本リモートセンシング学会誌, 44 (2), 127-134, https://doi.org/10.11440/rssj.2024.014,　2024 (査読無).
  • 24) Brodowsky, C. V., Sukhodolov, T., Chiodo, G., Aquila, V., Bekki, S., Dhomse, S. S., Höpfner, M., Laakso, A., Mann, G. W., Niemeier, U., Pitari, G., Quaglia, I., Rozanov, E., Schmidt, A., Sekiya, T., Tilmes, S., Timmreck, C., Vattioni, S., Visioni, D., Yu, P., Zhu, Y., and Peter, T.: Analysis of the global atmospheric background sulfur budget in a multi-model framework, Atmos. Chem. Phys., 24, 5513–5548, https://doi.org/10.5194/acp-24-5513-2024, 2024.
  • 23) Sekiya, T., Miyazaki, K., Eskes, H., Bowman, K., Sudo, K., Kanaya, Y., and Takigawa, M., The worldwide COVID-19 lockdown impacts on global secondary inorganic aerosols and radiative budget, Sci. Adv., 9, eadh2688, doi:10.1126/sciadv.adh2688, 2023
  • 22) Bisht, J. S. H., Patra, P. K., Takigawa, M., Sekiya, T., Kanaya, Y., Saitoh, N., and Miyazaki, K.: Estimation of CH4 emission based on an advanced 4D-LETKF assimilation system, Geosci. Model Dev., 16, 1823–1838, https://doi.org/10.5194/gmd-16-1823-2023, 2023.
  • 21) Takashima, H., Kanaya, Y., Kato, S., Friedrich, M. M., Van Roozendael, M., Taketani, F., Miyakawa, T., Komazaki, Y., Cuevas, C. A., Saiz-Lopez, A., and Sekiya, T., Full latitudinal marine atmospheric measurements of iodine monoxide, Atmos. Chem. Phys., 22, 4005–4018, https://doi.org/10.5194/acp-22-4005-2022, 2022.
  • 20) Sekiya, T., Miyazaki, K., Eskes, H., Sudo, K., Takigawa, M., and Kanaya, Y., A comparison of the impact of TROPOMI and OMI tropospheric NO2 on global chemical data assimilation, Atmos. Meas. Tech., 15, 1703–1728, https://doi.org/10.5194/amt-15-1703-2022, 2022.
  • 19) Miyazaki, K., Bowman, K., Sekiya, T., Takigawa, M., Neu, J. L., Sudo, K., Osterman, G., and Eskes, H., Global tropospheric ozone responses to reduced NOx emissions linked to the COVID-19 worldwide lockdowns, Sci. Adv., 7, 24, abf7460, https://doi.org/10.1126/sciadv.abf7460, 2021.
  • 18) Sekiya, T., Miyazaki, K., Ogochi, K., Sudo, K., Takigawa, M., Eskes, H., and Boersma, K. F., Impacts of horizontal resolution on global data assimilation of satellite measurements for tropospheric chemistry analysis, J. Adv. Model. Earth Syst., 13, e2020MS002180. https://doi.org/10.1029/2020MS002180, 2021
  • 17) Zhang, Y., West, J. J., Emmons, L. K., Flemming, J., Jonson, J. E., Lund, M. T., Sekiya, T., Sudo, K., Gaudel, A., Chang, K.-L., Nédélec, P., Thouret, V., Contributions of World Regions to the Global Tropospheric Ozone Burden Change from 1980 to 2010, Geophys. Res. Lett., 48, e2020GL089184. https://doi.org/10.1029/2020GL089184, 2021
  • 16) Miyazaki, K., Bowman, K., Sekiya, T., Jiang, Z., Chen, X., Eskes, H., Ru, M., Zhang, Y., Shindell, D., Air quality response in China linked to the 2019 novel coronavirus (COVID-19) lockdown, Geophys. Res. Lett., 47, e2020GL089252. https://doi.org/10.1029/2020GL089252, 2020
  • 15) Miyazaki, K., Bowman, K., Sekiya, T., Eskes, H., Boersma, F., Worden, H., Livesey, N., Payne, V. H., Sudo, K., Kanaya, Y., Takigawa, M., and Ogochi, K.: Updated tropospheric chemistry reanalysis and emission estimates, TCR-2, for 2005–2018, Earth Syst. Sci. Data, 12, 2223–2259, https://doi.org/10.5194/essd-12-2223-2020, 2020.
  • 14) Huijnen, V., Miyazaki, K., Flemming, J., Inness, A., Sekiya, T., and Schultz, M. G., An intercomparison of tropospheric ozone reanalysis products from CAMS, CAMS interim, TCR-1, and TCR-2, Geosci. Model Dev., 13, 1513–1544, https://doi.org/10.5194/gmd-13-1513-2020, 2020.
  • 13) Sekiya, T., Kanaya, Y., Sudo, K., Taketani, F., Iwamoto, Y., Aita, M. N., Yamamoto, A., Kawamoto, K., Global bromine- and iodine-mediated tropospheric ozone loss estimated using the CHASER chemical transport model, SOLA, 2020-037, https://doi.org/10.2151/sola.2020-037, 2020
  • 12) Kanaya, Y., Miyazaki, K., Taketani, F., Miyakawa, T., Takashima, H., Komazaki, Y., Pan, X., Kato, S., Sudo, K., Sekiya, T., Inoue, J., Sato, K., and Oshima, K., Ozone and carbon monoxide observations over open oceans on R/V Mirai from 67° S to 75° N during 2012 to 2017: testing global chemical reanalysis in terms of Arctic processes, low ozone levels at low latitudes, and pollution transport, Atmos. Chem. Phys., 19, 7233–7254, https://doi.org/10.5194/acp-19-7233-2019, 2019.
  • 11) Miyazaki, K., Sekiya, T., Fu, D., Bowman, K. W., Kulawik, S. S., Sudo, K., Walker, T., Kanaya, Y., Takigawa, M., Ogochi, K., Eskes, H., Boersma, K. F., Thompson, A. M., Gaubert, B., Barre, J., Emmons, L. K., Balance of emission and dynamical controls on ozone during the Korea-United States Air Quality campaign from multiconstituent satellite data assimilation. J. Geophys. Res., 124, 387– 413. https://doi.org/10.1029/2018JD028912, 2019
  • 10) Dong, X., Fu, J. S., Zhu, Q., Sun, J., Tan, J., Keating, T., Sekiya, T., Sudo, K., Emmons, L., Tilmes, S., Jonson, J. E., Schulz, M., Bian, H., Chin, M., Davila, Y., Henze, D., Takemura, T., Benedictow, A. M. K., and Huang, K., Long-range transport impacts on surface aerosol concentrations and the contributions to haze events in China: an HTAP2 multi-model study, Atmos. Chem. Phys., 18, 15581–15600, https://doi.org/10.5194/acp-18-15581-2018, 2018.
  • 9) Liang, C.-K., West, J. J., Silva, R. A., Bian, H., Chin, M., Davila, Y., Dentener, F. J., Emmons, L., Flemming, J., Folberth, G., Henze, D., Im, U., Jonson, J. E., Keating, T. J., Kucsera, T., Lenzen, A., Lin, M., Lund, M. T., Pan, X., Park, R. J., Pierce, R. B., Sekiya, T., Sudo, K., and Takemura, T., HTAP2 multi-model estimates of premature human mortality due to intercontinental transport of air pollution and emission sectors, Atmos. Chem. Phys., 18, 10497–10520, https://doi.org/10.5194/acp-18-10497-2018, 2018.
  • 8) Taketani, F., Aita, M.N., Yamaji, K., Sekiya, T., Ikeda, K., Sasaoka, K., Hashioka, T., Honda, M.C., Matsumoto., K., and Kanaya, Y., Seasonal Response of North Western Pacific Marine Ecosystems to Deposition of Atmospheric Inorganic Nitrogen Compounds from East Asia. Sci Rep 8, 9324, https://doi.org/10.1038/s41598-018-27523-w, 2018
  • 7) Galmarini, S., Kioutsioukis, I., Solazzo, E., Alyuz, U., Balzarini, A., Bellasio, R., Benedictow, A. M. K., Bianconi, R., Bieser, J., Brandt, J., Christensen, J. H., Colette, A., Curci, G., Davila, Y., Dong, X., Flemming, J., Francis, X., Fraser, A., Fu, J., Henze, D. K., Hogrefe, C., Im, U., Garcia Vivanco, M., Jiménez-Guerrero, P., Jonson, J. E., Kitwiroon, N., Manders, A., Mathur, R., Palacios-Peña, L., Pirovano, G., Pozzoli, L., Prank, M., Schultz, M., Sokhi, R. S., Sudo, K., Tuccella, P., Takemura, T., Sekiya, T., and Unal, A., Two-scale multi-model ensemble: is a hybrid ensemble of opportunity telling us more?, Atmos. Chem. Phys., 18, 8727–8744, https://doi.org/10.5194/acp-18-8727-2018, 2018.
  • 6) Sekiya, T., Miyazaki, K., Ogochi, K., Sudo, K., and Takigawa, M., Global high-resolution simulations of tropospheric nitrogen dioxide using CHASER V4.0, Geosci. Model Dev., 11, 959–988, https://doi.org/10.5194/gmd-11-959-2018, 2018.
  • 5) Patra, P.K., Crisp, D., Kaiser, J.W., Debra Wunch, Saeki, T., Ichii, K., Sekiya, T., Wennberg, P.O., Feist, D.G., Pollard, D.F., Griffith, D.W.T., Velazco, V.A., De Maziere, M., Sha, M.K., Roehl, C., Chatterjee, A., Ishijima, K., The Orbiting Carbon Observatory (OCO-2) tracks 2–3 peta-gram increase in carbon release to the atmosphere during the 2014–2016 El Niño, Sci Rep 7, 13567, https://doi.org/10.1038/s41598-017-13459-0, 2017.
  • 4) Kashimura, H., Abe, M., Watanabe, S., Sekiya, T., Ji, D., Moore, J. C., Cole, J. N. S., and Kravitz, B., Shortwave radiative forcing, rapid adjustment, and feedback to the surface by sulfate geoengineering: analysis of the Geoengineering Model Intercomparison Project G4 scenario, Atmos. Chem. Phys., 17, 3339–3356, https://doi.org/10.5194/acp-17-3339-2017, 2017.
  • 3) Sekiya, T., Sudo, K., and Nagai, T., Evolution of stratospheric sulfate aerosol from the 1991 Pinatubo eruption: Roles of aerosol microphysical processes, J. Geophys. Res. Atmos., 121, 2911– 2938, doi:10.1002/2015JD024313, 2016.
  • 2) Sekiya, T., and Sudo, K., Roles of transport and chemistry processes in global ozone change on interannual and multidecadal time scales”, J. Geophys. Res. Atmos., 119, 4903– 4921, doi:10.1002/2013JD020838, 2014.
  • 1) Sekiya, T., and Sudo, K., Role of meteorological variability in global tropospheric ozone during 1970–2008, J. Geophys. Res., 117, D18303, doi:10.1029/2012JD018054, 2012.