Hirata Takafumi

Arctic Research CenterSpecially Appointed Associate Professor
Last Updated :2025/11/06

■Researcher basic information

Degree

  • Ph.D., University of Copenhagen

Researchmap personal page

Home Page URL

J-Global ID

Research Keyword

  • Satellite Earth Observation
  • Oceanography
  • Radiative Transfer in Aquatic Medium
  • Integrated Marine Ecosystem Assessment
  • Bio-Optics

Research Field

  • Environmental science/Agricultural science, Environmental dynamics

Educational Organization

■Career

Career

  • 2024 - Present
    Hokkaido University, Arctic Research Center, S.A. Associate Professor, Cross-Regional Research Unit Leader
  • Apr. 2023 - Mar. 2024
    NPO Digital Hokkaido, Senior Researcher
  • Apr. 2019 - Mar. 2023
    Hokkaido University, Arctic Research Center, S.A. Associate Professor, Remote Sensing and Modelling Research Group Leader
  • Dec. 2019 - Feb. 2020
    ドイツ アルフレッドウェゲナー研究所 ヘルムホルツ極域海洋センター 客員研究員
  • 2009 - Mar. 2019
    Hokkaido University, Faculty of Environmental Earth Science
  • Jun. 2017 - Sep. 2017
    ドイツ ライプニッツ熱帯海洋生態研究センター 客員研究員
  • 2008 - 2009
    National Centre for Earth Observation (United Kingdom), Researcher
  • 2003 - 2009
    Plymouth Marine Laboratory (United Kingdom)
  • 2003 - 2008
    Centre for Observation of Air-Sea Interactions and Fluxes (United Kingdom)

Educational Background

  • 2003, University of Copenhagen, Niels Bohr Institute for Astronomy, Physics and Geophysics, (デンマーク政府奨学生), Denmark

Committee Memberships

  • Oct. 2024 - Present
    Hokkaido University, Forum for Space Research
  • Oct. 2024 - Present
    European Space Agency, ESA, Living Planet Scientific Committee Member
  • 2024 - Present
    North Pacific Marine Science Organization (PICES), Advisory Panel on the Arctic Ocean and the Pacific Gateways, Member
  • Jan. 2024 - Present
    International Arctic Science Committee (IASC), ICARP IV, Research Priority Team 3 Member
  • Jul. 2023 - Present
    Hokkaido Industry Academia Government Research Forum, Aerospace Research Research Committee
  • Feb. 2022 - Present
    Frontiers in Marine Science, Associate Editor
  • May 2023 - Mar. 2025
    当別町地域福祉計画策定委員会委員, Autonomy
  • Jun. 2020 - Jun. 2024
    North Pacific Marine Science Organization (PICES), Integrated Ecosystem Assessment of the Northern Bering Sea Working Group Member
  • Jun. 2023 - Mar. 2024
    当別町地球温暖化対策実行計画策定委員会委員, Autonomy
  • Nov. 2019 - Mar. 2023
    Japan Meteorological Agency, Research Promotion Group for the Utilization of Geostationary Meteorological Satellite Data, Society
  • Oct. 2021
    European Space Agency, Living Planet Scientific Committee Member, Others
  • 2016 - 2020
    JAXA, SGLI Working Group, Society
  • 2014 - 2018
    Japan Meteorological Agency, Satellite "Himawari" Data Utilization Working Group, Society
  • 2012 - 2017
    地球圏生物圏国際協同研究計画 (IGBP) / Future Earth /, AIMES (Analysis, Integration and Modeling of the Earth System) 科学委員, Society
  • 2012 - 2017
    Marine Ecosystem Model Intercomparison Project, Science Steering Committee, Society
  • 2014 - 2016
    International Ocean Colour Cordinating Group, Science Committee, Society
  • 2011 - 2013
    JAXA, Earth System Diagnosis Committee, Marine Domain Subcommittee, Society

■Research activity information

Papers

  • Towards an integrated assessment of the Arctic marine ecosystems in response to abrupt environmental changes: Contribution from the Arctic Challenge for Sustainability II (ArCS II) project (in press)
    Hirata, T., Alabia, I.D., Fujiwara, A., Fukai, Y., García Molinos, J., Kasai, A., Kawakami, T., Matsuno, K., Onodera, J., Shiozaki, T., Ueno, H., Watanabe, E.
    Polar Science, 101260, Aug. 2025, [Peer-reviewed], [Lead author]
    English, Scientific journal
  • Prospect of satellite ocean color remote sensing (in Japanese)　　　　　　　　　　　　　　　
    Takafumi Hirata
    Journal of Advanced Marine Science and Technology Society, 29, 49, 56, Apr. 2025, [Invited], [Lead author, Last author, Corresponding author]
    Japanese, Scientific journal
  • Future redistribution of fishery resources suggests biological and economic trade-offs according to the severity of the emission scenario
    Irene D. Alabia, Jorge García Molinos, Takafumi Hirata, Daiju Narita, Toru Hirawake
    PLOS ONE, 19, 6, e0304718, e0304718, Public Library of Science (PLoS), 06 Jun. 2024, [Peer-reviewed]
    English, Scientific journal, Climate change is anticipated to have long-term and pervasive effects on marine ecosystems, with cascading consequences to many ocean-reliant sectors. For the marine fisheries sector, these impacts can be further influenced by future socio-economic and political factors. This raises the need for robust projections to capture the range of potential biological and economic risks and opportunities posed by climate change to marine fisheries. Here, we project future changes in the abundance of eight commercially important fish and crab species in the eastern Bering Sea and Chukchi Sea under different CMIP6 Shared Socioeconomic Pathways (SSPs) leading to contrasting future (2021–2100) scenarios of warming, sea ice concentration, and net primary production. Our results revealed contrasting patterns of abundance and distribution changes across species, time periods and climate scenarios, highlighting potential winners and losers under future climate change. In particular, the least changes in future species abundance and distribution were observed under SSP126. However, under the extreme scenario (SSP585), projected Pacific cod and snow crab abundances increased and decreased, respectively, with concurrent zonal and meridional future shifts in their centers of gravity. Importantly, projected changes in species abundance suggest that fishing at the same distance from the current major port in the Bering Sea (i.e., Dutch Harbor) could yield declining catches for highly valuable fisheries (e.g., Pacific cod and snow crab) under SSP585. This is driven by strong decreases in future catches of highly valuable species despite minimal declines in maximum catch potential, which are dominated by less valuable taxa. Hence, our findings show that projected changes in abundance and shifting distributions could have important biological and economic impacts on the productivity of commercial and subsistence fisheries in the eastern Bering and Chukchi seas, with potential implications for the effective management of transboundary resources.
  • Pan-Arctic marine biodiversity and species co-occurrence patterns under recent climate
    Irene D. Alabia, Jorge García Molinos, Takafumi Hirata, Franz J. Mueter, Carmen L. David
    Scientific Reports, 13, 1, Springer Science and Business Media LLC, 11 Mar. 2023, [Peer-reviewed]
    English, Scientific journal, Abstract

    The Arctic region is experiencing drastic climatic changes bringing about potential ecological shifts. Here, we explored marine biodiversity and potential species associations across eight Arctic marine areas between 2000 and 2019. We compiled species occurrences for a subset of 69 marine taxa (i.e., 26 apex predators and 43 mesopredators) and environmental factors to predict taxon-specific distributions using a multi-model ensemble approach. Arctic-wide temporal trends of species richness increased in the last 20 years and highlighted potential emerging areas of species accrual due to climate-driven species redistribution. Further, regional species associations were dominated by positive co-occurrences among species pairs with high frequencies in the Pacific and Atlantic Arctic areas. Comparative analyses of species richness, community composition, and co-occurrence between high and low summer sea ice concentrations revealed contrasting impacts of and detected areas vulnerable to sea ice changes. In particular, low (high) summer sea ice generally resulted in species gains (loss) in the inflow and loss (gains) in the outflow shelves, accompanied by substantial changes in community composition and therefore potential species associations. Overall, the recent changes in biodiversity and species co-occurrences in the Arctic were driven by pervasive poleward range shifts, especially for wide-ranging apex predators. Our findings highlight the varying regional impacts of warming and sea ice loss on Arctic marine communities and provide important insights into the vulnerability of Arctic marine areas to climate change.
  • Acclimation by diverse phytoplankton species determines oceanic carbon to nitrogen ratios
    Yoshio Masuda, Yasuhiro Yamanaka, Sherwood Lan Smith, Takafumi Hirata, Hideyuki Nakano, Akira Oka, Hiroshi Sumata, Maki Noguchi Aita
    Limnology and Oceanography Letters, Wiley, 14 Jan. 2023, [Peer-reviewed]
    Scientific journal
  • Relative contributions of photophysiology and chlorophyll-a abundance to phytoplankton group-specific primary production in the Kuroshio region as inferred by satellite ocean color remote sensing (in press)
    Takafumi Hirata, Koji Suzuki
    Journal of Oceanography, Mar. 2022, [Peer-reviewed], [Lead author]
    English, Scientific journal
  • Photoacclimation by phytoplankton determines the distribution of global subsurface chlorophyll maxima in the ocean
    Yoshio Masuda, Yasuhiro Yamanaka, Sherwood Lan Smith, Takafumi Hirata, Hideyuki Nakano, Akira Oka, Hiroshi Sumata
    Communications Earth & Environment, 2, 1, Springer Science and Business Media LLC, Dec. 2021, [Peer-reviewed], [International Magazine]
    Scientific journal, AbstractSubsurface chlorophyll maxima are widely observed in the ocean, and they often occur at greater depths than maximum phytoplankton biomass. However, a consistent mechanistic explanation for their distribution in the global ocean remains lacking. One possible mechanism is photoacclimation, whereby phytoplankton adjust their cellular chlorophyll content in response to environmental conditions. Here, we incorporate optimality-based photoacclimation theory based on resource allocation trade-off between nutrient uptake and light harvesting capacity into a 3D biogeochemical ocean circulation model to determine the influence of resource allocation strategy on phytoplankton chlorophyll to carbon ratio distributions. We find that photoacclimation is a common driving mechanism that consistently explains observed global scale patterns in the depth and intensity of subsurface chlorophyll maxima across ocean regions. This mechanistic link between cellular-scale physiological responses and the global scale chlorophyll distribution can inform interpretation of ocean observations and projections of phytoplankton responses to climate change.
  • Research and Development of a Supporting Information System for Optimization of Salmon Release Operations and Monitoring the Coastal Environment on the Okhotsk Coast, Japan
    Sei-Ichi Saitoh, Yasuyuki Miyakoshi, Fumihiro Takahashi, Takafumi Hirata, Irene Alabia, Takashi Hosokawa, Tatsuya Miyoshi
    Technical Report, 17, North Pacific Anadromous Fish Commission, 29 Nov. 2021
    Scientific journal
  • Performance of JAXA’s SGLI standard ocean color products for oceanic to coastal waters: chlorophyll a concentration and light absorption coefficients of colored dissolved organic matter
    Atsushi Matsuoka, Janet W. Campbell, Stanford B. Hooker, François Steinmetz, Kazunori Ogata, Takafumi Hirata, Hiroto Higa, Victor S. Kuwahara, Tomonori Isada, Koji Suzuki, Toru Hirawake, Joji Ishizaka, Hiroshi Murakami
    Journal of Oceanography, 78, 4, 187, 208, 23 Oct. 2021, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Phytoplankton Increase Along the Kuroshio Due to the Large Meander
    Daniel Andres Lizarbe Barreto, Ricardo Chevarria Saravia, Takeyoshi Nagai, Takafumi Hirata
    Frontiers in Marine Science, 8, Frontiers Media SA, 10 Aug. 2021, [Peer-reviewed], [Last author], ［Internationally co-authored］, [International Magazine]
    Scientific journal, The Kuroshio Large Meander (LM) is known to be highly aperiodic and can last from 1 to 10 years. Since a stationary cold core formed between the Kuroshio and the southern coast of Japan off Enshu-Nada and approaching warm saltier water on the eastern side of the LM changes the local environment drastically, many commercially valuable fish species distribute differently from the non-LM period, impacting local fisheries. Despite this importance of the LM, the influences of the LM on the low trophic levels such as phytoplankton and zooplankton have still been unclear. In this study, satellite daily sea surface chlorophyll data are analyzed in relation to the LM. The results show positive anomalies of the chlorophyll-a concentration along the Kuroshio path during the LM periods, 2004–2005 and 2017–2019, from the upstream off Shikoku to the downstream (140°E). These positive anomalies are started by the triggering meander generated off south of Kyushu, which then slowly propagates to the downstream LM region in both the LM periods. Even though the detailed patterns along the Kuroshio region in the two LM periods were different, similar formations of the positive anomalies on the western side of the LM with shallower mixed layer depth are observed. Furthermore, we found clear relationships between the minimum distance from several stations along the coast to the Kuroshio axis and the mean chlorophyll-a anomaly, with significant correlations with the distance from different stations.
  • Marine biodiversity refugia in a climate‐sensitive subarctic shelf
    Irene D. Alabia, Jorge García Molinos, Takafumi Hirata, Franz J. Mueter, Toru Hirawake, Sei‐Ichi Saitoh
    Global Change Biology, 27, 14, 3299, 3311, Wiley, Jul. 2021, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    Scientific journal
  • Radiometric calibration for a multispectral sensor onboard risesat microsatellite based on lunar observations
    Masataka Imai, Junichi Kurihara, Toru Kouyama, Toshinori Kuwahara, Shinya Fujita, Yuji Sakamoto, Yuji Sato, Sei Ichi Saitoh, Takafumi Hirata, Hirokazu Yamamoto, Yukihiro Takahashi
    Sensors, 21, 7, Apr. 2021, [Peer-reviewed], [International Magazine]
    Scientific journal
  • Lunar Calibration and its Validation for a Multispectral Sensor Onboard Risesat Microsatellite.
    Masataka Imai, Junichi Kurihara, Toru Kouyama, Toshinori Kuwahara, Shinya Fujita 0002, Yuji Sakamoto, Sei-Ichi Saitoh, Takafumi Hirata, Hirokazu Yamamoto, Yuji Sato, Yukihiro Takahashi
    IEEE International Geoscience and Remote Sensing Symposium(IGARSS), 7775, 7778, IEEE, 2021
    International conference proceedings
  • Inhibition of competitive exclusion due to phytoplankton dispersion: a contribution for solving Hutchinson's paradox
    YoshioMasuda, YasuhiroYamanaka, Takafumi Hirata, Hideyuki Nakano, Takashi S.Kohyama
    Ecological Modelling, 430, https://doi.org/10.1016/j.ecolmodel.2020.109089, 109089, Elsevier BV, Aug. 2020, [Peer-reviewed], [International Magazine]
    English, Scientific journal
  • Multiple facets of marine biodiversity in the Pacific Arctic under future climate
    Irene D. Alabia, Jorge García Molinos, Sei-Ichi Saitoh, Takafumi Hirata, Toru Hirawake, Franz J. Mueter
    Science of The Total Environment, 744, https://doi.org/10.1016/j.scitotenv.2020.140913, 140913, Elsevier BV, 2020, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    Scientific journal
  • Satellite Ocean Colour: Current Status and Future Perspective　　　　　　　　　　　　　　　
    Steve Groom, Shubha Sathyendranath, Yai Ban, Stewart Bernard, Robert Brewin, Vanda Brotas, Carsten Brockmann, Prakash Chauhan, Jong-kuk Choi, Andrei Chuprin, Stefano Ciavatta, Paolo Cipollini, Craig Donlon, Bryan Franz, Xianqiang He, Takafumi Hirata, Tom Jackson, Milton Kampel, Hajo Krasemann, Samantha Lavender, Silvia Pardo-Martinez, Frédéric Mélin, Trevor Platt, Rosalia Santoleri, Jozef Skakala, Blake Schaeffer, Marie Smith, Francois Steinmetz, Andre Valente, Menghua Wang
    Frontiers in Marine Science, 6:485, doi: 10.3389/fmars.2019.00485, 2019, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Biological data assimilation for parameter estimation of a phytoplankton functional type model for the western North Pacific
    Yasuhiro Hoshiba, Takafumi Hirata, Masahito Shigemitsu, Hideyuki Nakano, Taketo Hashioka, Yoshio Masuda, Yasuhiro Yamanaka
    Ocean Science, 14, 3, 371, 386, 2018, [Peer-reviewed], [International Magazine]
    English, Scientific journal
  • Distribution shifts of marine taxa in the Pacific Arctic under contemporary climate changes　　　　　　　　　　　　　　　
    Irene D. Alabia, Jorge García Molinos, Sei-Ichi Saitoh, Toru Hirawake, Takafumi Hirata, Franz J. Muete
    Diversity and Distributions, DOI: 10.1111/ddi.12788, Nov. 2017, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • A synthesis of the environmental response of the North and South Atlantic Sub-Tropical Gyres during two decades of AMT
    Jim Aiken, Robert J.W. Brewin, Francois Dufois, Luca Polimene, Nick J. Hardman-Mountford, Thomas Jackson, Ben Loveday, Silvana Mallor Hoya, Giorgio Dall'Olmo, John Stephens, Takafumi Hirata
    Progress in Oceanography, 158, 236, 254, Elsevier Ltd, 01 Nov. 2017, [Peer-reviewed], [Last author], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Obtaining phytoplankton diversity from ocean color: A scientific roadmap for future development
    Astrid Bracher, Heather A. Bouman, Robert J.W. Brewin, Annick Bricaud, Vanda Brotas, Aurea M. Ciotti, Lesley Clementson, Emmanuel Devred, Annalisa Di Cicco, Stephanie Dutkiewicz, Nick J. Hardman-Mountford, Anna E. Hickman, Martin Hieronymi, Takafumi Hirata, Svetlana N. Losa, Colleen B. Mouw, Emanuele Organelli, Dionysios E. Raitsos, Julia Uitz, Meike Vogt, Aleksandra Wolanin
    Frontiers in Marine Science, 4, Frontiers Media S. A, 03 Mar. 2017, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Inter-comparison of phytoplankton functional type phenology metrics derived from ocean color algorithms and Earth System Models
    Tihomir S. Kostadinov, Anna Cabre, Harish Vedantham, Irina Marinov, Astrid Bracher, Robert J. W. Brewin, Annick Bricaud, Takafumi Hirata, Toru Hirawake, Nick J. Hardman-Mountford, Colleen Mouw, Shovonlal Roy, Julia Uitz
    REMOTE SENSING OF ENVIRONMENT, 190, 162, 177, Mar. 2017, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • A consumer's guide to satellite remote sensing of multiple phytoplankton groups in the global ocean
    Colleen B. Mouw, Nick J. Hardman-Mountford, Séverine Alvain, Astrid Bracher, Robert J. W. Brewin, Annick Bricaud, Aurea M. Ciotti, Emmanuel Devred, Amane Fujiwara, Takafumi Hirata, Toru Hirawake, Tihomir S. Kostadinov, Shovonlal Roy, Julia Uitz
    Frontiers in Marine Science, 4, Frontiers Media S. A, 21 Feb. 2017, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Competition and community assemblage dynamics within a phytoplankton functional group: Simulation using an eddy-resolving model to disentangle deterministic and random effects
    Yoshio Masuda, Yasuhiro Yamanaka, Takafumi Hirata, Hideyuki Nakano
    ECOLOGICAL MODELLING, 343, 1, 14, Jan. 2017, [Peer-reviewed], [International Magazine]
    English, Scientific journal
  • Development of models for simulating linkages among physical, ecological, and human systems
    Takahashi K, N Saigusa, T. Oikawa, M. Kawamiya, T. Hajima, Y. Yamanaka, T. Hirata, A. Abe-Ouchi
    地球環境, 20, 2, 135, 142, 国際環境研究協会, 2015, [Peer-reviewed], [Domestic magazines]
    Japanese, Scientific journal
  • Drivers and uncertainties of future global marine primary production in marine ecosystem models
    C. Laufkoetter, M. Vogt, N. Gruber, M. Aita-Noguchi, O. Aumont, L. Bopp, E. Buitenhuis, S. C. Doney, J. Dunne, T. Hashioka, J. Hauck, T. Hirata, J. John, C. Le Quere, I. D. Lima, H. Nakano, R. Seferian, I. Totterdell, M. Vichi, C. Voelker
    BIOGEOSCIENCES, 12, 23, 6955, 6984, 2015, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Global Retrieval of Diatom Abundance Based on Phytoplankton Pigments and Satellite Data
    Mariana A. Soppa, Takafumi Hirata, Brenner Silva, Tilman Dinter, Ilka Peeken, Sonja Wiegmann, Astrid Bracher
    REMOTE SENSING, 6, 10, 10089, 10106, Oct. 2014, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Bio-optical properties during the summer season in the Sea of Okhotsk
    Shintaro Takao, Takahiro Iida, Tomonori Isada, Sei-Ichi Saitoh, Takafumi Hirata, Koji Suzuki
    PROGRESS IN OCEANOGRAPHY, 126, 233, 241, Aug. 2014, [Peer-reviewed], [International Magazine]
    English, Scientific journal
  • Development and verification of GCOM-C1/SGLI ocean algorithms
    Hirata, T, T. Hirawake, F. Sakaida, Yamaguchi, K. Suzuki, H. Murakami, J. Ishizaka, H. Kobayashi, A. Fujiwara, M. Toratani, S. Saitoh
    Journal of the Remote Sensing Society of Japan, 34, 4, 278, 285, 2014, [Peer-reviewed], [Domestic magazines]
    English, Scientific journal
  • Impacts of light shading and nutrient enrichment geo-engineering approaches on the productivity of a stratified, oligotrophic ocean ecosystem
    Nick J. Hardman-Mountford, Luca Polimene, Takafumi Hirata, Robert J. W. Brewin, Jim Aiken
    Journal of the Royal Society Interface, 10, 89, Royal Society, 06 Dec. 2013, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • The distribution, dominance patterns and ecological niches of plankton functional types in Dynamic Green Ocean Models and satellite estimates
    M. Vogt, T. Hashioka, M. R. Payne, E. T. Buitenhuis, C. Le Quéré, S. Alvain, M. N. Aita, L. Bopp, S. C. Doney, T. Hirata, I. Lima, S. Sailley, Y. Yamanaka
    Copernicus GmbH, 04 Nov. 2013
    Abstract. We compare the spatial and temporal representation of phytoplankton functional types (pPFTs) in four different Dynamic Green Ocean Models (DGOMs; CCSM-BEC, NEMURO, PISCES and PlankTOM5) to derived phytoplankton distributions from two independent satellite estimates, with a particular focus on diatom distributions. Global annual mean surface biomass estimates for diatoms vary between 0.23 mmol C m−3 and 0.77 mmol C m−3 in the models, and are comparable to a satellite-derived estimate (0.41 mmol C m−3). All models consistently simulate a higher zonal mean diatom biomass contribution in the high latitudes than in the low latitudes, but the relative diatom contribution varies substantially between models with largest differences in the high latitudes (20% to 100% of total biomass). We investigate phytoplankton distribution in terms of annual and monthly mean dominance patterns, i.e. the distribution of locations where a given PFT contributes more than 50% to total biomass. In all models, diatoms tend to dominate large areas of the high latitudes of both hemispheres, and the area of the surface ocean dominated by diatoms is significantly higher in the models than in the satellite estimates. We estimate the realized ecological niches filled by the dominant pPFT at each location as a function of annual mean surface nitrate concentration (NO3), sea surface temperature (SST), and mixed layer depth. A general additive model (GAM) is used to map the probability of dominance of all pPFTs in niche and geographic space. Models tend to simulate diatom dominance over a wider temperature and nutrient range, whereas satellites confine diatom dominance to a narrower niche of low-intermediate annual mean temperatures (annual mean SST < 10 °C), but allow for niches in different ranges of surface NO3 concentrations. For annual mean diatom dominance, the statistically modelled probability of dominance explains the majority of the variance in the data (65.2–66.6%). For the satellite estimates, the explained deviance is much lower (44.6% and 32.7%). The differences in the representation of diatoms among models and compared to satellite estimates highlights the need to better resolve phytoplankton succession and phenology in the models. This work is part of the marine ecosystem inter-comparison project (MAREMIP).
  • Generalized ocean color inversion model for retrieving marine inherent optical properties
    P. Jeremy Werdell, Bryan A. Franz, Sean W. Bailey, Gene C. Feldman, Emmanuel Boss, Vittorio E. Brando, Mark Dowell, Takafumi Hirata, Samantha J. Lavender, Zhong Ping Lee, Hubert Loisel, Stéphane Maritorena, Fréderic Mélin, Timothy S. Moore, Timothy J. Smyth, David Antoine, Emmanuel Devred, Odile Hembise Fanton D'Andon, Antoine Mangin
    Applied Optics, 52, 10, 2019, 2037, OSA - The Optical Society, 01 Apr. 2013, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Phytoplankton competition during the spring bloom in four plankton functional type models
    T. Hashioka, M. Vogt, Y. Yamanaka, C. Le Quere, E. T. Buitenhuis, M. N. Aita, S. Alvain, L. Bopp, T. Hirata, I. Lima, S. Sailley, S. C. Doney
    BIOGEOSCIENCES, 10, 11, 6833, 6850, 2013, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Distribution of phytoplankton functional types in high-nitrate, low-chlorophyll waters in a new diagnostic ecological indicator model
    A. P. Palacz, M. A. St John, R. J. W. Brewin, T. Hirata, W. W. Gregg
    BIOGEOSCIENCES, 10, 11, 7553, 7574, 2013, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • A comparison between phytoplankton community structures derived from a global 3D ecosystem model and satellite observation
    Takafumi Hirata, Stephane Saux-Picart, Taketo Hashioka, Maki Aita-Noguchi, Hiroshi Sumata, Masahito Shigemitsu, J. Icarus Allen, Yasuhiro Yamanaka
    Journal of Marine Systems, 109-110, 129, 137, Jan. 2013, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • The influence of the Indian Ocean Dipole on interannual variations in phytoplankton size structure as revealed by Earth Observation
    Robert J. W. Brewin, Takafumi Hirata, Nick J. Hardman-Mountford, Samantha J. Lavender, Shubha Sathyendranath, Ray Barlow
    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, 77-80, 117, 127, Nov. 2012, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Comparing satellite-based phytoplankton classification methods
    Takafumi Hirata, Nick Hardman-Mountford, Robert J. W. Brewin
    Eos, 93, 6, 59, 60, 2012, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • An intercomparison of bio-optical techniques for detecting dominant phytoplankton size class from satellite remote sensing
    Robert J. W. Brewin, Nick J. Hardman-Mountford, Samantha J. Lavender, Dionysios E. Raitsos, Takafumi Hirata, Julia Uitz, Emmanuel Devred, Annick Bricaud, Aurea Ciotti, Bernard Gentili
    REMOTE SENSING OF ENVIRONMENT, 115, 2, 325, 339, Feb. 2011, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Synoptic relationships between surface Chlorophyll-a and diagnostic pigments specific to phytoplankton functional types
    T. Hirata, N. J. Hardman-Mountford, R. J. W. Brewin, J. Aiken, R. Barlow, K. Suzuki, T. Isada, E. Howell, T. Hashioka, M. Noguchi-Aita, Y. Yamanaka
    BIOGEOSCIENCES, 8, 2, 311, 327, 2011, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • A three-component model of phytoplankton size class for the Atlantic Ocean
    Robert J. W. Brewin, Shubha Sathyendranath, Takafumi Hirata, Samantha J. Lavender, Rosa M. Barciela, Nick J. Hardman-Mountford
    ECOLOGICAL MODELLING, 221, 11, 1472, 1483, Jun. 2010, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Marine ecosystem models for earth systems applications: The MarQUEST experience
    J. Icarus Allen, James Aiken, Thomas R. Anderson, Erik Buitenhuis, Sarah Cornell, Richard J. Geider, Keith Haines, Takafumi Hirata, Jason Holt, Corinne Le Quere, Nicholas Hardman-Mountford, Oliver N. Ross, Bablu Sinha, James While
    JOURNAL OF MARINE SYSTEMS, 81, 1-2, 19, 33, Apr. 2010, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • A spectral response approach for detecting dominant phytoplankton size class from satellite remote sensing
    Robert J. W. Brewin, Samantha J. Lavender, Nick J. Hardman-Mountford, Takafumi Hirata
    ACTA OCEANOLOGICA SINICA, 29, 2, 14, 32, Mar. 2010, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • An inherent optical property approach to the estimation of size-specific photosynthetic rates in eastern boundary upwelling zones from satellite ocean colour: An initial assessment
    Takafumi Hirata, Nick J. Hardman-Mountford, Ray Barlow, Tarron Lamont, Robert Brewin, Tim Smyth, James Aiken
    PROGRESS IN OCEANOGRAPHY, 83, 1-4, 393, 397, Oct. 2009, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Relationship between the distribution function of ocean nadir radiance and inherent optical properties for oceanic waters
    Takafumi Hirata, Nicholas Hardman-Mountford, James Aiken, James Fishwick
    APPLIED OPTICS, 48, 17, 3129, 3138, Jun. 2009, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • An objective methodology for the classification of ecological pattern into biomes and provinces for the pelagic ocean
    Nick J. Hardman-Mountford, Takafumi Hirata, Kirsten A. Richardson, Jim Aiken
    REMOTE SENSING OF ENVIRONMENT, 112, 8, 3341, 3352, Aug. 2008, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Estimation of the in situ UV-A absorption of seawater by a simple irradiance inversion model
    Hirata, T
    Journal of Oceanography, 64, 4, 561, 566, Aug. 2008, [Peer-reviewed], [International Magazine]
    English, Scientific journal
  • An absorption model to determine phytoplankton size classes from satellite ocean colour
    T. Hirata, J. Aiken, N. Hardman-Mountford, T. J. Smyth, R. G. Barlow
    REMOTE SENSING OF ENVIRONMENT, 112, 6, 3153, 3159, Jun. 2008, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Relationship between the irradiance reflectance and inherent optical properties of seawater
    Takafumi Hirata, Niels K. Hojerslev
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 113, C3, Mar. 2008, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Functional links between bioenergetics and bio-optical traits of phytoplankton taxonomic groups: an overarching hypothesis with applications for ocean colour remote sensing
    Jim Aiken, Nick J. Hardman-Mountford, Ray Barlow, James Fishwick, Takafumi Hirata, Tim Smyth
    JOURNAL OF PLANKTON RESEARCH, 30, 2, 165, 181, Feb. 2008, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Numerical radiative transfer simulations to examine shape of the phase function of suspended particles on the ocean colour reflectance
    Hirata, T, G. F. Moore
    La Mer, 45, 2, 91, 98, 日仏海洋学会, 2007, [Peer-reviewed], [Lead author], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Semianalytical model for the derivation of ocean color inherent optical properties: description, implementation, and performance assessment (vol 46, pg 429, 2007)
    T. J. Smyth, G. F. Moore, T. Hirata, J. Aiken
    APPLIED OPTICS, 46, 3, 429, 430, Jan. 2007, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Semianalytical model for the derivation of ocean color inherent optical properties: description, implementation, and performance assessment
    Timothy J. Smyth, Gerald F. Moore, Takafumi Hirata, James Aiken
    APPLIED OPTICS, 45, 31, 8116, 8131, Nov. 2006, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal
  • Irradiance inversion theory to retrieve volume scattering function of seawater
    T Hirata
    APPLIED OPTICS, 42, 9, 1564, 1573, Mar. 2003, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
    English, Scientific journal

Other Activities and Achievements

Books and other publications

  • Encyclopedia of Remote Sensing (in Japanese)　　　　　　　　　　　　　　　
    Estimation of the normalized water leaving radiance
    Remote Sensing Society of Japan / Maruzen Publishing, Dec. 2022, 9784621307762, [Contributor]
  • Encyclopedia of Remote Sensing (in Japanese)　　　　　　　　　　　　　　　
    Estimation of the inherent optical properties
    Remote Sensing Society of Japan / Maruzen Publishing, Dec. 2022, 9784621307762, [Contributor]
  • Advances in Phytoplankton Ecology　　　　　　　　　　　　　　　
    Chapter 7: Applications of satellite remote sensing technology to the analysis of phytoplankton community structure on large scales
    Dec. 2021, [Joint work]

Affiliated academic society

  • 日本海洋学会　　　　　　　　　　　　　　　
  • The Optical Society of America　　　　　　　　　　　　　　　
  • 日本地球惑星科学連合　　　　　　　　　　　　　　　
  • American Geophysical Union　　　　　　　　　　　　　　　

Research Themes

  • Application of the satellite remote sensing of coastal algal community to harmful algal bloom monitoring　　　　　　　　　　　　　　　
    4th Research Announcement on the Earth Observations
    Apr. 2025 - Mar. 2028
    JAXA, 北海道大学, Principal investigator
  • 海洋生態系解析のためのSGLI海色プロダクトの検証と改良　　　　　　　　　　　　　　　
    第3回地球観測研究公募
    Apr. 2022 - Mar. 2025
    JAXA, Principal investigator
  • Arctic biodiversity change and its consequences: Assessing, monitoring and predicting the effects of ecosystem tipping cascades on marine ecosystem services and dependent human systems　　　　　　　　　　　　　　　
    Horizon2020
    Jun. 2020 - May 2024
    European Commission (欧州委員会), Coinvestigator not use grants
  • Study on sea ice condition and navigability risk of Northern Sea Route
    Grants-in-Aid for Scientific Research
    01 Apr. 2021 - 31 Mar. 2024
    大塚 夏彦, 平田 貴文
    本年度は、①変形氷域を特定するための衛星データの収集と基本的な分析、②航行実態と海氷による航行障害事例を把握するための船舶航行軌跡の収集と整理、ならびに海氷状況と実際の航行速度の関係の基本的な分析を行い、本研究の主目的である変形氷域およびそれによる航行障害の把握を行うための基本的な知見を得るとともに、実際的な研究手法について検討した。
    ①については、C-Band合成開口レーダー(SAR)観測データ(Sentinel-1)において、Beaufort Gyre Exploration Project（BGEP）がボーフォート海で実施している海氷ドラフト観測点を含む観測データを抽出し、顕著な変形氷と思われる大きな海氷ドラフト観測時における、SAR観測における後方散乱係数ならびに氷盤等の状況を比較分析した。これより、長径が5~40kmとなる平坦で大きな氷盤が連なる海域において、氷盤の間で局所的に後方散乱係数が大きくなる数km程度の範囲の氷域が認められ、これが大きなドラフトを呈する変形氷域であることが予想された。
    ②については、北極海航路を航行した貨物船の航行記録（衛星AIS）と、航行時の海氷状況（TOPAZ4 データ同化システム）を収集整理し、氷海航行におけるリスクマネジメントシステムPOLARIS（国際海事機関IMOによる）を用いて、船のアイスクラスと海氷状況より算出されるリスクインデックスRIOを求め、実際の航行速度と対比した。この結果、海氷による航行障害の発生事例において、RIOは航行障害による速度低下事象と比較的よく相関するが、ここで用いている密接度と氷厚だけでは十分に説明できないこと、氷盤サイズや密集度および局所的な変形氷域の影響を考慮する必要性を認識した（学会発表）。
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 21K04511
  • Sustainable use of salmon resources under climate change using composite satellite data　　　　　　　　　　　　　　　
    JAXA 3rd Earth Observation Research Announcement
    Apr. 2022 - Mar. 2024
    Sei-Ichi Saitoh (PI), Yasuyuki Miyakoshi, Takafumi Hirata, Irene D. Alabia
    Japan Aerospace Exploration Agency, RA3MAF006
  • 小型衛星 RISESAT 搭載海洋観測カメラによる観測とその応用　　　　　　　　　　　　　　　
    2019 - 2024
    株）パスコ
  • 海洋植物プランクトンに関する形質空間の概念確立と気候変動に伴う将来予測
    Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Apr. 2018 - Mar. 2023
    山中 康裕, 平田 貴文
    本年度は海洋におけるクロロフィル濃度分布の形成メカニズムを明らかにした論文が、Nature系の新雑誌であるCommunications Earth & Environmentに受理された。また、植物プランクトンが細胞内の炭素・窒素比を環境に応じて変化させるメカニズムを明らかにした論文を投稿した。
    海洋のクロロフィル濃度は表層でなく亜表層で最大値を取る。この亜表層クロロフィル極大は海洋には普遍的に存在するが、特定の海域を除いて、形成される原因が明確でなかった。受理された論文では世界で初めて亜表層クロロフィル極大の全球分布の再現に成功し、植物プランクトンが細胞内のクロロフィル含有量を環境に応じて変化させることで全ての海域の亜表層クロロフィル極大の形成が説明できると明らかにした。この論文は細胞スケールの生理がグローバルスケールの現象を決めるメカニスティックな基礎となることを示している。
    植物プランクトン細胞の炭素・窒素比は光合成によって海洋に固定される炭素量と海洋表層に供給される窒素量の比であり、海洋の炭素循環と窒素循環をリンクさせる役割を果たす。もし、気候変動に伴って植物プランクトン細胞の炭素・窒素比が変わると海洋が吸収するCO2量が変わる。投稿中の論文では植物プランクトン細胞の炭素・窒素比の変化は、生体資源の最適化によって説明できることを明らかにした。また、海洋全体で平均した植物プランクトンの炭素・窒素比は伝統的に用いられていたRedfield比より大きくなることを示した、これは光合成による海洋のCO2吸収量は、従来考えられていたよりも大きいことを意味する。
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 18H04130
  • 再帰反射構造を有しＳＡＲ衛星で観測可能な海上浮力体の研究開発　　　　　　　　　　　　　　　
    SCOPE 戦略的情報通信研究開発推進事業
    2019 - 2022
    総務省, 北極域研究センター, Coinvestigator
  • 衛星を利用した持続可能なサケ資源生産支援プロジェクト　　　　　　　　　　　　　　　
    課題解決に向けた先進的な衛星リモートセンシングデータ利用モデル実証プロジェクト
    Aug. 2020 - Mar. 2021
    内閣府, Coinvestigator
  • SGLI/GCOM-C 海色アルゴリズムの改良と海色プロダクトの検証および応用　　　　　　　　　　　　　　　
    2nd Research Announcement on the Earth Observations
    2019 - 2021
    Takafumi Hirata
    JAXA, Principal investigator, Competitive research funding
  • 衛星データを利用した北極域における海洋モニタリングに関する研究　　　　　　　　　　　　　　　
    2019 - 2020
    Green & Life Innovation, Inc., Coinvestigator
  • 画像処理技術と生物光学を融合した新型海洋一次生産者別基礎生産算出アルゴリズム　　　　　　　　　　　　　　　
    Grants-in-aid for scientific Research
    2017 - Mar. 2019
    Takafumi Hirata
    Japan Society For The Promotion of Science, Principal investigator, Competitive research funding
  • Calibration, Validation and Application of the SGLI/GCOM-C ocean algorithms　　　　　　　　　　　　　　　
    地球環境変動観測ミッション第６回研究公募
    Apr. 2016 - Mar. 2019
    平田貴文
    JAXA, Principal investigator, Competitive research funding
  • A novel algorithm to estimate marine primary production using bio-optics and image processing
    Grants-in-Aid for Scientific Research
    01 Apr. 2015 - 31 Mar. 2018
    HIRATA Takafumi, MURAKAMI Hiroshi
    A satellite remote sensing algorithm was developed to estimate the group-specific primary production of marine phytoplankton. A novelty of the algorithm is that it integrates bio-optical modeling with image processing. Analysis of the 10-year long satellite data of the group-specific primary production obtained from the new algorithm showed that 1) the photosynthetic rate is different among the groups and 2) factors affecting variability of the photosynthetic rate also differ among the groups: the photosynthetic rate of diatoms are mainly regulated by their biomass, whereas that of cyanobacteria by photo-physiology. The rate of haptophytes are affected by both their biomass and photo-physiology, depending on season/months in consideration.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 15K00513
  • 画像処理技術と生物光学を融合した新型海洋一次生産者別基礎生産算出アルゴリズム　　　　　　　　　　　　　　　
    Grants-in-aid for scientific Research
    Apr. 2016 - Mar. 2018
    Takafumi Hirata
    Japan Society For The Promotion of Science, Principal investigator, Competitive research funding
  • Development and calibration of GCOM-C ocean algorithms to derive marine biogeochemical and ecosystem variables towards satellite-model integrated analysis　　　　　　　　　　　　　　　
    地球環境変動観測ミッション第４回研究公募
    Apr. 2013 - Mar. 2016
    Takafumi Hirata
    JAXA, Principal investigator, Competitive research funding
  • Ocean Color Climate Change Initiative　　　　　　　　　　　　　　　
    Climate Change Initiative
    2014 - 2016
    European Space Agency, Ocean Colour Climate Change Initiative
  • Development of GCOM-C Ocean algorithm to derive Ecosystem Indicators for a satellite-model integrated analysis of marine ecosystem function and global biogeochemical cycles　　　　　　　　　　　　　　　
    地球環境変動観測ミッション第２回研究公募
    2009 - Mar. 2013
    Takafumi Hirata
    JAXA, Principal investigator, Competitive research funding
  • 総長室事業推進経費
    2013 - 2013
    平田貴文
    北海道大学, Principal investigator, Competitive research funding
  • 海色衛星観測と生態系モデルによる一次生産者群集構造と海洋二酸化炭素分圧との関係　　　　　　　　　　　　　　　
    Grants-in-aid for scientific Research
    2010 - 2011
    Takafumi Hirata
    Japan Society For The Promotion of Science, Principal investigator, Competitive research funding
  • Irradiance inversion to estimate the volume scattering function of natural waters　　　　　　　　　　　　　　　
    助成金
    2000
    スカンジナビア・ニッポン ササカワ財団, コペンハーゲン大学, Principal investigator