Updated on 2024/12/09

Information

 

写真a

 
MORI MASATO
 
Organization
Research Institute for Applied Mechanics Division of Earth Environment Dynamics Assistant Professor
Interdisciplinary Graduate School of Engineering Sciences Department of Interdisciplinary Engineering Sciences(Concurrent)
Title
Assistant Professor
Profile
My research interests include atmospheric circulation variability that cause extreme weather events. We aim to understand climate variability and change by clarifying the mechanisms and predictability of atmospheric circulation variability and estimating (attribution) the impact of external factors such as global warming on that through climate diagnostics using reanalysis data and numerical experiments using dynamical models and global climate models.

Research Areas

  • Natural Science / Atmospheric and hydrospheric sciences

Research History

  • Kyushu University Research Institute for Applied Mechanics Assistant Professor 

    2020.9 - Present

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  • The University of Tokyo Research Center for Advanced Science and Technology Assistant Professor 

    2016.4 - 2020.8

  • The University of Tokyo Atmosphere and Ocean Research Institute Specially Appointed Assistant Professor 

    2014.8 - 2016.3

  • The University of Tokyo Atmosphere and Ocean Research Institute Academic Researcher 

    2008.4 - 2014.7

Education

  • 北海道大学大学院   地球環境科学研究科   大気海洋圏環境科学専攻 博士課程

    - 2008

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    Country:Japan

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  • 北海道大学大学院   地球環境科学研究科   大気海洋圏環境科学専攻 修士課程

    - 2004

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    Country:Japan

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  • Shizuoka University   Faculty of Science   Department of Physics

    - 2002

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    Country:Japan

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Research Interests・Research Keywords

  • Research theme: 異常気象

    Keyword: 異常気象

    Research period: 2008 - Present

  • Research theme: 地球温暖化

    Keyword: 地球温暖化

    Research period: 2008 - Present

  • Research theme: Climate Dynamics

    Keyword: Climate Dynamics

    Research period: 2008 - Present

  • Research theme: Atmosphere-Ocean-Sea Ice Interaction

    Keyword: Atmosphere-Ocean-Sea Ice coupling, Teleconnection

    Research period: 2021.4 - Present

  • Research theme: Impacts of global warming-induced Arctic sea ice change on the mid-latitude atmosphere

    Keyword: Arctic sea ice variability, remote influence, global warming, extreme weather, Arctic, sea ice

    Research period: 2013.4 - Present

  • Research theme: Seasonal and near-term prediction of tropical cyclone activity over the Western North Pacific

    Keyword: tropical cyclone, seasonal prediction, near-term prediction, CGCM

    Research period: 2011.4 - 2013.3

  • Research theme: Understanding the formation mechanism of the atmospheric general circulation in the tropics using aqua planet experiments

    Keyword: aqua planet, superrotation, Hadley Circulation, Walker Circulation

    Research period: 2008.4 - 2010.3

  • Research theme: Dynamics of the Pacific/North American Teleconnection Pattern

    Keyword: PNA, MJO, teleconnection, low-frequency variability, storm track

    Research period: 2002.4 - 2008.3

Awards

  • 日本気象学会気象集誌論文賞(2013年)

    2013.11   日本気象学会  

Papers

  • Robust Arctic sea-ice influence on the frequent Eurasian cold winters in past decades Reviewed International journal

    Masato Mori, Masahiro Watanabe, Hideo Shiogama, Jun Inoue, Masahide Kimoto

    Nature Geoscience   7 ( 12 )   869 - 873   2014.12

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    Over the past decade, severe winters occurred frequently in mid-latitude Eurasia(1,2), despite increasing global- and annual-mean surface air temperatures(3). Observations suggest that these cold Eurasian winters could have been instigated by Arctic sea-ice decline(2,4), through excitation of circulation anomalies similar to the Arctic Oscillation(5). In climate simulations, however, a robust atmospheric response to sea-ice decline has not been found, perhaps owing to energetic internal fluctuations in the atmospheric circulation(6). Here we use a 100-member ensemble of simulations with an atmospheric general circulation model driven by observation-based sea-ice concentration anomalies to show that as a result of sea-ice reduction in the Barents-Kara Sea, the probability of severe winters has more than doubled in central Eurasia. In our simulations, the atmospheric response to sea-ice decline is approximately independent of the Arctic Oscillation. Both reanalysis data and our simulations suggest that sea-ice decline leads to more frequent Eurasian blocking situations, which in turn favour cold-air advection to Eurasia and hence severe winters. Based on a further analysis of simulations from 22 climate models we conclude that the sea-ice-driven cold winters are unlikely to dominate in a warming future climate, although uncertainty remains, due in part to an insufficient ensemble size.

    DOI: 10.1038/NGEO2277

  • What Determines the East Asian Winter Temperature during El Nino?-Role of the Early Onset El Nino and Tropical Indian Ocean Warming Reviewed International journal

    Shiozaki, M; Tokinaga, H; Mori, M

    Journal of Climate   37 ( 15 )   4031 - 4043   2024.8   ISSN:0894-8755 eISSN:1520-0442

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    Atmospheric teleconnections from the Pacific El Niño are key to determining the East Asian winter climate. Using the database for policy decision-making for future climate change (d4PDF) large-ensemble simulations, the present study investigates a mechanism for the warm and cold East Asian winters during El Niño with a focus on atmospheric teleconnections triggered by anomalous sea surface temperature (SST) patterns in the tropical Indo-Pacific. Our results show that the western Pacific (WP) teleconnection pattern plays a primary role in the warm winters in East Asia. The WP pattern tends to appear in years when both an early El Niño and the positive phase of the Indian Ocean dipole (IOD) mode develop in boreal autumn. In those years, the tropical Indian Ocean (TIO) strongly warms in the following winter, forming a distinct zonal contrast in precipitation anomalies over the tropical Indo-Pacific through a reduced Walker circulation. The Rossby wave source anomalies indicate that the WP pattern is associated with the weakened Indo-Pacific Walker circulation. By contrast, the WP pattern does not dominate in the cold winters due to the absence of strong TIO warming. The present study proposes a mechanism that promotes the excitation of the WP pattern through the upper-troposphere divergence in East Asia associated with the Walker circulation modulated by the tropical Indo-Pacific interbasin interaction. SIGNIFICANCE STATEMENT: The East Asian winter temperature variability is controlled not only by the strong atmospheric internal variability in the midlatitudes and high latitudes but also by remote forcing from the tropical ocean. Our study investigates how El Niño exerts diverse impacts on the East Asian winter temperature, depending on where atmospheric convection intensifies in the tropical Pacific Ocean and the Indian Ocean. Our results show that an intense warming of the tropical Indian Ocean and the early development of El Niño are the major factors for warm winters in East Asia. Given that a precursor of the intense Indian Ocean warming appears in boreal autumn, our findings should contribute to the improvement of seasonal prediction for the East Asian winter climate.

    DOI: 10.1175/JCLI-D-23-0627.1

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  • The Influence of Extratropical Ocean on the PNA Teleconnection: Role of Atmosphere-Ocean Coupling Reviewed International journal

    Mori, M; Tokinaga, H; Kosaka, Y; Nakamura, H; Taguchi, B; Tatebe, H

    Geophysical Research Letters   51 ( 14 )   2024.7   ISSN:0094-8276 eISSN:1944-8007

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Geophysical Research Letters  

    The Pacific/North American (PNA) pattern is a major low-frequency variability in boreal winter. A recent modeling study suggested that PNA variability increases through extratropical atmosphere-ocean coupling, but the effect was not fully extracted due to a particular experimental design. By comparing coupled and two sets of uncoupled large-ensemble global model simulations, here we show that the PNA-induced horseshoe-shaped sea-surface temperature (SST) anomaly in the North Pacific returns a non-negligible influence on the PNA itself. Its magnitude depends on the presence or absence of atmosphere-ocean coupling. The coupling accounts for ∼16% of the PNA variance, while the horseshoe-shaped SST anomaly explains only 5% under the uncoupled condition. The coupling reduces the damping of available potential energy by modulating turbulent heat fluxes and precipitation, magnifying the PNA variance. Precipitation processes in the extratropics as well as tropics are therefore important for realistically representing PNA variability and thereby regional weather and climate.

    DOI: 10.1029/2024GL110234

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  • Northern Hemisphere winter atmospheric teleconnections are intensified by extratropical ocean-atmosphere coupling Reviewed International journal

    Masato Mori, Yu Kosaka, Bunmei Taguchi, Hiroki Tokinaga, Hiroaki Tatebe, Hisashi Nakamura

    Communications Earth & Environment   5 ( 1 )   2024.3   eISSN:2662-4435

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    Abstract

    The role of extratropical atmosphere-ocean coupling in generating and maintaining large-scale atmospheric low-frequency variability remains an open question owing to vigorous atmospheric internal fluctuations. Here, we use coupled and uncoupled large-ensemble global model simulations to clarify how the coupling intensifies atmospheric teleconnection patterns in the Northern Hemisphere winter. We show that the extratropical coupling selectively enhances the variance of three principal modes of variability, explaining 13%, 11%, and 10% of the total variance of Pacific/North American, North Atlantic Oscillation, and Warm-Arctic Cold-Eurasian patterns, respectively. Atmosphere-ocean coupling reduces damping to lower-tropospheric available potential energy, which in turn increases kinetic energy by changing energy transfer within the mode. The extratropical ocean is overall passive (adjustable) to large-scale atmospheric variation, thus contributing to the prominence of these modes. The geographical dependence of available potential energy damping suggests the existence of mode-specific sweet spots where the influence of coupling operates efficiently, providing a clue to improving the model biases in variance and signal-to-noise ratio of these modes.

    DOI: 10.1038/s43247-024-01282-1

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    Other Link: https://www.nature.com/articles/s43247-024-01282-1

    Repository Public URL: https://hdl.handle.net/2324/7178881

  • Global Historical Reanalysis with a 60-km AGCM and Surface Pressure Observations: OCADA Reviewed International journal

    Ishii, M., H. Kamahori, H. Kubota, M. Zaiki, R. Mizuta, H. Kawase, M. Nosaka, H. Yoshimura, N. Oshima, E. Shindo, H. Koyama, M. Mori, S. Hirahara, Y. Imada, K. Yoshida, T. Nozawa, T. Takemi, T. Maki, A. Nishimura

    Journal of the Meteorological Society of Japan   102 ( 2 )   209 - 240   2024.3

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    DOI: https://doi.org/10.2151/jmsj.2024-010

    Repository Public URL: https://hdl.handle.net/2324/7177974

  • Barents-Kara sea-ice decline attributed to surface warming in the Gulf Stream Reviewed International journal

    Yoko Yamagami, Masahiro Watanabe, Masato Mori, Jun Ono

    Nature Communications   13 ( 1 )   3767   2022.12   eISSN:20411723

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    Decline in winter sea-ice concentration (SIC) in the Barents-Kara Sea significantly impacts climate through increased heat release to the atmosphere. However, the past Barents-Kara SIC decrease rate is underestimated in the majority of Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models. Here we show that climate model simulations can reproduce the Barents-Kara SIC trend for 1970–2017 when sea surface temperature (SST) variability in the Gulf Stream region is constrained by observations. The constrained warming of the Gulf Stream strengthens ocean heat transport to the Barents-Kara Sea that enhances the SIC decline. The linear trends between the SIC and SST are highly correlated in the CMIP6 ensemble, suggesting that the externally forced component of the Gulf Stream SST increase explains up to 56% of the forced Barents-Kara SIC trend. Therefore, future warming of the Gulf Stream can be an essential pacemaker of the SIC decline.

    DOI: 10.1038/s41467-022-31117-6

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    Repository Public URL: https://hdl.handle.net/2324/7161069

  • Arctic sea ice loss and Eurasian cooling in winter 2020−21 Reviewed International journal

    Kazuaki Nishii, Bunmei Taguchi, Masato Mori, Yu Kosaka, and Hisashi Nakamura

    SOLA   18   199 - 204   2022.9

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    DOI: doi:10.2151/sola.2022-032

    Repository Public URL: https://hdl.handle.net/2324/7161187

  • Robust but weak winter atmospheric circulation response to future Arctic sea ice loss Reviewed International coauthorship International journal

    D. Smith, R. Eade, M. Andrews, H. Ayres, A. Clark, S. Chripko, C. Deser, N. J. Dunstone, J. Garcia-Serrano, G. Gastineau, L. S. Graff, S. C. Hardiman, B. He, L. Hermanson, T. Jung, J. Knight, X. Levine, G. Magnusdottir, E. Manzini, D. Matei, M. Mori, R. Msadek, P. Ortega, Y. Peings, A. A. Scaife, J. A. Screen, M. Seabrook, T. Semmler, M. Sigmond, J. Streffing, L. Sun, A. Walsh

    Nature Communications   13 ( 1 )   727   2022.2   eISSN:20411723

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:NATURE PORTFOLIO  

    The possibility that Arctic sea ice loss weakens mid-latitude westerlies, promoting more severe cold winters, has sparked more than a decade of scientific debate, with apparent support from observations but inconclusive modelling evidence. Here we show that sixteen models contributing to the Polar Amplification Model Intercomparison Project simulate a weakening of mid-latitude westerlies in response to projected Arctic sea ice loss. We develop an emergent constraint based on eddy feedback, which is 1.2 to 3 times too weak in the models, suggesting that the real-world weakening lies towards the higher end of the model simulations. Still, the modelled response to Arctic sea ice loss is weak: the North Atlantic Oscillation response is similar in magnitude and offsets the projected response to increased greenhouse gases, but would only account for around 10% of variations in individual years. We further find that relationships between Arctic sea ice and atmospheric circulation have weakened recently in observations and are no longer inconsistent with those in models.

    DOI: 10.1038/s41467-022-28283-y

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    Repository Public URL: https://hdl.handle.net/2324/7161646

  • Trends and projection of heavy snowfall in Hokkaido, Japan as an application of self-organizing map Reviewed International journal

    Masaru Inatsu, Sho Kawazoe, Masato Mori

    Journal of Applied Meteorology and Climatology   2021.9

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    <title>Abstract</title>This paper showed the frequency of local-scale heavy winter snowfall in Hokkaido, Japan, its historical change, and its response to global warming using self-organizing map (SOM) of synoptic-scale sea-level pressure anomaly. Heavy snowfall days were here defined as days when the snowfall exceeded 10 mm in water equivalent. It was shown that the SOMs can be grouped into three categories for heavy snowfall days: 1) a passage of extratropical cyclones to the south of Hokkaido, 2) a pressure pattern between the Siberian high and the Aleutian low, and 3) a low-pressure anomaly just to the east of Hokkaido. Groups 1 and 2 were associated with heavy snowfall in Hiroo (located in southeastern Hokkaido) and in Iwamizawa (western Hokkaido), respectively, and heavy snowfall in Sapporo (western Hokkaido) was related to Group 3. The large-ensemble historical simulation reproduced the observed increasing trend in Group 2 and future projection revealed that Group 2 was related to a negative phase of the Western Pacific pattern and the frequency of this group would increase in the future. Heavy snowfall days associated with SOM Group 2 would also increase due to the increase in water vapor and preferable weather patterns in global warming climate, in contrast to the decrease of heavy snowfall days in other sites associated with SOM Group 1.

    DOI: 10.1175/jamc-d-21-0085.1

    Repository Public URL: https://hdl.handle.net/2324/7177966

  • Reply to: Eurasian cooling in response to Arctic sea-ice loss is not proved by maximum covariance analysis Reviewed International journal

    Masato Mori, Yu Kosaka, Masahiro Watanabe, Bunmei Taguchi, Hisashi Nakamura, Masahide Kimoto

    Nature Climate Change   11 ( 2 )   109 - 111   2021.2

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    DOI: 10.1038/s41558-020-00983-7

    Repository Public URL: https://hdl.handle.net/2324/7177950

  • Impact of air–sea coupling on the probability of occurrence of heat waves in Japan Reviewed International journal

    Akira Hasegawa, Yukiko Imada, Hideo Shiogama, Masato Mori, Hiroaki Tatebe, Masahiro Watanabe

    Progress in Earth and Planetary Science   7 ( 1 )   2020.12

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    In extreme event attribution, which aims to answer whether and to what extent a particular extreme weather event can be attributed to global warming, the probability of an event is generally estimated through large ensemble simulations, using an atmospheric general circulation model (AGCM). In islands, such as Japan, it has been considered that surface air temperature (SAT) can be significantly affected by the surrounding sea surface temperature (SST), which mostly is affected by atmospheric circulation at mid- and high-latitudes. Therefore, the absence of SST responses to atmospheric variability in AGCMs impacts the estimation of the occurrence of extreme events, such as heat waves in Japan. In this study, we examined the impact of air–sea coupling on the probability of occurrence of severe heat waves that occurred in Japan in the summer of 2010 by analyzing the probability differences obtained from AGCM and coupled general circulation model (CGCM) large-ensemble experiments. The observed ocean temperature, salinity, and sea ice were assimilated in the 100-member CGCM experiments, as they were assigned as boundary conditions in the 100-member AGCM experiments. The SAT around Japan in the northern summer is largely related to the Bonin high, whose interannual variability is largely affected by the Silk Road and Pacific-Japan (PJ) pattern teleconnections in the real world. The SAT anomaly over Japan was related to the pressure variability due to the Silk Road and PJ patterns in the CGCM experiment. By contrast, the SAT over Japan simulated by AGCM was less sensitive to such pressure variability, and the SAT ensemble spread became narrower in AGCM. The results suggest that the probability of occurrence of the 2010 heat wave in Japan would tend to be underestimated by the AGCM ensemble compared to the CGCM ensemble, provided that the ensemble averages of the SAT anomalies were equal between CGCM and AGCM experiments. This study raised the issue of the absence of SST response to atmospheric variability in AGCMs, which can critically impact the estimation of extreme event probability, particularly in mid-latitude islands, such as Japan. [Figure not available: see fulltext.]

    DOI: 10.1186/s40645-020-00390-8

    Repository Public URL: https://hdl.handle.net/2324/7177949

  • Modulations of north american and european weather variability and extremes by interdecadal variability of the atmospheric circulation over the north atlantic sector Reviewed International journal

    Patrick Martineau, Hisashi Nakamura, Yu Kosaka, Bunmei Taguchi, Masato Mori

    Journal of Climate   33 ( 18 )   8125 - 8146   2020.9

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    The dominant mode of wintertime interdecadal covariability between subseasonal surface air temperature (SAT) variability and midtropospheric circulation over the North Atlantic sector is identified through maximum covariance analysis applied to century-long reanalysis data. This mode highlights a tendency for subseasonal temperature variability over Europe and eastern North America to be enhanced during decades when the negative phase of the North Atlantic Oscillation (NAO) prevails. This interdecadal NAO is characterized by a stationary Rossby wave train that originates from the subtropical Atlantic, propagates northward into the subpolar Atlantic, and finally refracts toward Europe and the Middle East. A decadal increase in precipitation in the subtropics under the enhanced supply of heat and moisture from the Gulf Stream and its surroundings appears to act as a source for this wave train. The influence of the interdecadal NAO on subseasonal SAT variability is explained primarily by the modulated efficiency of baroclinic conversion of available potential energy from the background atmospheric flow to subseasonal eddies. The combination of enhanced subseasonal variability and low winter-mean temperature anomalies associated with the negative phase of the interdecadal NAO increases the frequency of cold extremes affecting Europe and the eastern United States.

    DOI: 10.1175/JCLI-D-19-0977.1

  • Reply to: Is sea-ice-driven Eurasian cooling too weak in models? Reviewed International journal

    Masato Mori, Yu Kosaka, Masahiro Watanabe, Bunmei Taguchi, Hisashi Nakamura, Masahide Kimoto

    Nature Climate Change   9 ( 12 )   937 - 939   2019.12

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    DOI: 10.1038/s41558-019-0636-0

  • Description and basic evaluation of simulated mean state, internal variability, and climate sensitivity in MIROC6 Reviewed International journal

    Tatebe Hiroaki, Ogura Tomoo, Nitta Tomoko, Komuro Yoshiki, Ogochi Koji, Takemura Toshihiko, Sudo Kengo, Sekiguchi Miho, Abe Manabu, Saito Fuyuki, Chikira Minoru, Watanabe Shingo, Mori Masato, Hirota Nagio, Kawatani Yoshio, Mochizuki Takashi, Yoshimura Kei, Takata Kumiko, O'ishi Ryouta, Yamazaki Dai, Suzuki Tatsuo, Kurogi Masao, Kataoka Takahito, Watanabe Masahiro, Kimoto Masahide

    Geoscientific Model Development   12 ( 7 )   2727 - 2765   2019.7

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    Description and basic evaluation of simulated mean state, internal variability, and climate sensitivity in MIROC6
    © 2019 Copernicus GmbH. All rights reserved. The sixth version of the Model for Interdisciplinary Research on Climate (MIROC), called MIROC6, was cooperatively developed by a Japanese modeling community. In the present paper, simulated mean climate, internal climate variability, and climate sensitivity in MIROC6 are evaluated and briefly summarized in comparison with the previous version of our climate model (MIROC5) and observations. The results show that the overall reproducibility of mean climate and internal climate variability in MIROC6 is better than that in MIROC5. The tropical climate systems (e.g., summertime precipitation in the western Pacific and the eastward-propagating Madden-Julian oscillation) and the midlatitude atmospheric circulation (e.g., the westerlies, the polar night jet, and troposphere-stratosphere interactions) are significantly improved in MIROC6. These improvements can be attributed to the newly implemented parameterization for shallow convective processes and to the inclusion of the stratosphere. While there are significant differences in climates and variabilities between the two models, the effective climate sensitivity of 2.6K remains the same because the differences in radiative forcing and climate feedback tend to offset each other. With an aim towards contributing to the sixth phase of the Coupled Model Intercomparison Project, designated simulations tackling a wide range of climate science issues, as well as seasonal to decadal climate predictions and future climate projections, are currently ongoing using MIROC6.

    DOI: 10.5194/gmd-12-2727-2019

  • A reconciled estimate of the influence of Arctic sea-ice loss on recent Eurasian cooling Reviewed International journal

    Masato Mori, Yu Kosaka, Masahiro Watanabe, Hisashi Nakamura, Masahide Kimoto

    Nature Climate Change   9   123 - 129   2019.1

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    A reconciled estimate of the influence of Arctic sea-ice loss on recent Eurasian cooling

    DOI: 10.1038/s41558-018-0379-3

  • The Effects of Natural Variability and Climate Change on the Record Low Sunshine over Japan During August 2017 Reviewed International journal

    Takahashi C, H. Shiogama, Y. Imada, Y. Kosaka, M. Mori, M. Arai, Y. Kamae, M. Watanabe

    Bulletin of the American Meteorological Society   100 ( 1 )   S67 - S71   2018.12

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    The Effects of Natural Variability and Climate Change on the Record Low Sunshine over Japan During August 2017

    DOI: 10.1175/BAMS-D-18-0107.1

  • The influences of El Nino and Arctic sea-ice on the QBO disruption in February 2016 Reviewed International journal

    N. Hirota, H. Shiogama, H. Akiyoshi, T. Ogura, M. Takahashi, Y. Kawatani, M. Kimoto, M. Mori

    npj Climate & Atmospheric Science   1   2018.1

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    The westerly phase of the quasi-biennial oscillation (QBO) was unexpectedly disrupted by an anomalous easterly near 40 hPa (similar to 23 km) in February 2016. At the same time, a very strong El Nino and a very low Arctic sea-ice concentration in the Barents and Kara Sea were present. Previous studies have shown that the disruption of the QBO was primarily caused by the momentum transport of the atmospheric waves in the Northern Hemisphere. Our results indicate that the tropical waves evident over the Atlantic, Africa, and the western Pacific were associated with extratropical disturbances. Moreover, we suggest that the El Nino and sea-ice anomalies in 2016 account for approximately half of the disturbances and waves based on multiple regression analysis of the observational/reanalysis data and large-ensemble experiments using an atmospheric global climate model.

    DOI: 10.1038/s41612-018-0020-1

  • Mechanisms for the Maintenance of the Wintertime Basin-Scale Atmospheric Response to Decadal SST Variability in the North Pacific Subarctic Frontal Zone Reviewed International journal

    Satoru Okajima, Hisashi Nakamura, Kazuaki Nishii, Takafumi Miyasaka, Akira Kuwano-Yoshida, Bunmei Taguchi, Masato Mori, Yu Kosaka

    JOURNAL OF CLIMATE   31 ( 1 )   297 - 315   2018.1

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    Mechanisms for the maintenance of a large-scale wintertime atmospheric response to warm sea surface temperature (SST) anomalies associated with decadal-scale poleward displacement of the North Pacific subarctic frontal zone (SAFZ) are investigated through the following two ensemble experiments with an atmospheric general circulation model (AGCM): one with climatological-mean SST and the other with positive SST anomalies along the SAFZ prescribed on top of the climatological-mean SST. As actually observed, the simulated January ensemble response over the North Pacific is anticyclonic throughout the depth of the troposphere, although its amplitude is smaller. This response is maintained through energy conversion from the ensemble climatological-mean circulation realized under the climatological SST as well as feedback from anomalous transient eddy activity, suggesting that the response may have characteristics as a preferred mode of variability (or "dynamical mode''). Conversions of both available potential energy and kinetic energy from the climatological-mean state are important for the observed anomaly, while the latter is less pronounced for the model response. Net transient feedback forcing is also important for both the observed anomaly and simulated response. These results imply that a moderate-resolution (similar to 1 degrees) AGCM may be able to simulate a basin-scale atmospheric response to the SAFZ SST anomaly through synoptic-and basin-scale dynamical processes. Weaker PNA-like internal variability in the model may lead to the weaker response, suggesting that misrepresentation of intrinsic atmospheric variability can affect the model response to the SST anomaly.

    DOI: 10.1175/JCLI-D-17-0200.1

  • CLIMATE CHANGE INCREASED THE LIKELIHOOD OF THE 2016 HEAT EXTREMES IN ASIA Reviewed International journal

    Imada Yukiko, Shiogama Hideo, Takahashi Chiharu, Watanabe Masahiro, Mori Masato, Kamae Youichi, Maeda Shuhei

    Bulletin of the American Meteorological Society   99 ( 1 )   S97 - S101   2018.1

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    CLIMATE CHANGE INCREASED THE LIKELIHOOD OF THE 2016 HEAT EXTREMES IN ASIA

    DOI: 10.1175/BAMS-D-17-0109.1

  • Impact of Lateral Boundary Errors on the Simulation of Clouds with a Nonhydrostatic Regional Climate Model Reviewed International journal

    Uchida, Junya, Mori, Masato, Hara, Masayuki, Satoh, Masaki, Goto, Daisuke, Kataoka, Takahito, Suzuki, Kentaroh, Nakajima, Teruyuki

    MONTHLY WEATHER REVIEW   145 ( 12 )   5059 - 5082   2017.12

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    A nonhydrostatic, regional climate limited-area model (LAM) was used to analyze lateral boundary condition (LBC) errors and their influence on the uncertainties of regional models. Simulations using the fully compressible nonhydrostatic LAM (D-NICAM) were compared against the corresponding global quasi-uniform-grid Nonhydrostatic Icosahedral Atmospheric Model (NICAM) and a stretched-grid counterpart (S-NICAM). By this approach of sharing the same dynamical core and physical schemes, possible causes of model bias and LBC errors are isolated. The simulations were performed for a 395-day period from March 2011 through March 2012 with horizontal grid intervals of 14, 28, and 56 km in the region of interest. The resulting temporal mean statistics of the temperatures at 500 hPa were generally well correlated between the global and regional simulations, indicating that LBC errors had a minor impact on the large-scale flows. However, the time-varying statistics of the surface precipitation showed that the LBC errors lead to the unpredictability of convective precipitation, which affected the mean statistics of the precipitation distributions but induced only minor influences on the large-scale systems. Specifically, extratropical cyclones and orographic precipitation are not severely affected. It was concluded that the errors of the precipitation distribution are not due to the difference of the model configurations but rather to the uncertainty of the system itself. This study suggests that applications of ensemble runs, internal nudging, or simulations with longer time scales are needed to obtain more statistically significant results of the precipitation distribution in regional climate models.

    DOI: 10.1175/MWR-D-17-0158.1

  • Significant Aerosol Influence on the Recent Decadal Decrease in Tropical Cyclone Activity Over the Western North Pacific Reviewed International journal

    Chiharu Takahashi, Masahiro Watanabe, Masato Mori

    GEOPHYSICAL RESEARCH LETTERS   44 ( 18 )   9496 - 9504   2017.9

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    Over the past two decades, the number of tropical cyclones (TCs) has decreased markedly in the southeastern part of the western North Pacific (WNP) as a component of the interdecadal variation. This decrease has partially been explained by an internal low-frequency variability of sea surface temperature (SST) in the Pacific, but influences of external forcing remain unclear. Here we show that past changes in sulfate aerosol emissions contributed approximately 60% of the observed decreasing trends in TC genesis frequency in the southeastern WNP for 1992-2011, using multiple simulations by a global climate model. This decrease was mainly attributed to the increased vertical wind shear and decreased low-level vorticity, associated with a trans-basin multidecadal SST change driven by aerosol forcing. The near-future projection shows that the aerosol forcing still has some potential influence on decadal TC change, but the projected decreasing frequency is mainly due to increasing greenhouse gases forcing.

    DOI: 10.1002/2017GL075369

  • Forced response and internal variability of summer climate over western North America Reviewed International journal

    Youichi Kamae, Hideo Shiogama, Yukiko Imada, Masato Mori, Osamu Arakawa, Ryo Mizuta, Kohei Yoshida, Chiharu Takahashi, Miki Arai, Masayoshi Ishii, Masahiro Watanabe, Masahide Kimoto, Shang-Ping Xie, Hiroaki Ueda

    CLIMATE DYNAMICS   49 ( 1-2 )   403 - 417   2017.7

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    Over the past decade, anomalously hot summers and persistent droughts frequented over the western United States (wUS), the condition similar to the 1950s and 1960s. While atmospheric internal variability is important for mid-latitude interannual climate variability, it has been suggested that anthropogenic external forcing and multidecadal modes of variability in sea surface temperature, namely, the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO), also affect the occurrence of droughts and hot summers. In this study, 100-member ensemble simulations for 1951-2010 by an atmospheric general circulation model were used to explore relative contributions of anthropogenic warming, atmospheric internal variability, and atmospheric response to PDO and AMO to the decadal anomalies over the wUS. By comparing historical and sensitivity simulations driven by observed sea surface temperature, sea ice, historical forcing agents, and non-warming counterfactual climate forcing, we found that large portions of recent increases in mean temperature and frequency of hot summers (66 and 82 %) over the wUS can be attributed to the anthropogenic global warming. In contrast, multidecadal change in the wUS precipitation is explained by a combination of the negative PDO and the positive AMO after the 2000s. Diagnostics using a linear baroclinic model indicate that AMO- and PDO-related diabatic heating anomalies over the tropics contribute to the anomalous atmospheric circulation associated with the droughts and hot summers over wUS on multidecadal timescale. Those anomalies are not robust during the periods when PDO and AMO are in phase. The prolonged PDO-AMO antiphase period since the late twentieth century resulted in the substantial component of multidecadal anomalies in temperature and precipitation over the wUS.

    DOI: 10.1007/s00382-016-3350-x

  • OVER 5,000 YEARS OF ENSEMBLE FUTURE CLIMATE SIMULATIONS BY 60-KM GLOBAL AND 20-KM REGIONAL ATMOSPHERIC MODELS Reviewed International journal

    Ryo Mizuta, Akihiko Murata, Masayoshi Ishii, Hideo Shiogama, Kenshi Hibino, Nobuhito Mori, Osamu Arakawa, Yukiko Imada, Kohei Yoshida, Toshinori Aoyagi, Hiroaki Kawase, Masato Mori, Yasuko Okada, Tomoya Shimura, Toshiharu Nagatomo, Mikiko Ikeda, Hirokazu Endo, Masaya Nosaka, Miki Arai, Chiharu Takahashi, Kenji Tanaka, Tetsuya Takemi, Yasuto Tachikawa, Khujanazarov Temur, Youichi Kamae, Masahiro Watanabe, Hidetaka Sasaki, Akio Kitoh, Izuru Takayabu, Eiichi Nakakita, Masahide Kimoto

    BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY   98 ( 7 )   1383 - 1398   2017.7

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    An unprecedentedly large ensemble of climate simulations with high-resolution atmospheric models enables the assessment of probabilistic change by global warming in low-frequency local-scale severe events.

    DOI: 10.1175/BAMS-D-16-0099.1

  • Corrigendum to: An event attribution of the 2010 drought in the South Amazon region using the MIROC5 model: Event attribution of the 2010 Amazon drought (Atmospheric Science Letters, (2013), 14, 3, (170-175), 10.1002/asl2.435) Reviewed International journal

    Hideo Shiogama, Masahiro Watanabe, Yukiko Imada, Masato Mori, Masayoshi Ishii, Masahide Kimoto

    Atmospheric Science Letters   18 ( 2 )   103 - 104   2017.2

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    As it has been reported by Shiogama et al. (, hereafter S16), the first half of 100 member ALL-forcing runs of Shiogama et al. (, hereafter S13) have the well mixed greenhouse gas concentrations of the year 1850 instead of that in the year 2006–2010 by an error. We have redone these experiments with the correct GHGs concentrations (S16). This error correction made little changes in the results and did not affect the conclusions of S13. The corrected Figures and are very similar to that in S13. The probabilities of drought events of ALL more at least as severe as the 2010 record is the same as S13 (1%) (see the first paragraph of the results section in page 172). With the bias corrections of ANSG and ENSO, the probabilities of drought events of ALL more at least as severe as the 2010 record are 14%. &lt
    3%, &gt
    29%, while those were 15% &lt
    5%, &gt
    32% in S13 (see the first paragraph of the right column of page 173). The ratios of ALL/NAT and noCS/ALL are 5.0 &lt
    2.9, 8.0 &gt
    (6.3 &lt
    3.2, 8.7 &gt
    in S13) and 1.1 &lt
    0.9, 1.3 &gt
    (1.0 &lt
    0.8, 1.1 &gt
    in S13), respectively (see the first paragraph of the right column of page 173). This error correction did not affect the other figures. 2 (Figure presented.) The black and 10 gray curves are probability density functions (PDF) of the Jul-Oct precipitation anomalies (%, relative to the 1979–2010 mean) during the 1979–2010 period for the observations and ALL-Long, respectively. The PDF is calculated as a normalized histogram of samples within half-overlapped 6%-width bins. The black vertical line is the 2010 observation. The green, blue, and red curves indicate the PDFs of the ALL, NAT, and noCS runs, respectively. Note that these PDFs were calculated from different numbers of samples: 32 for the observations and ALL-Long, and 100 for ALL, NAT and noCS. 4 (Figure presented.) The dashed green, blue, and red curves are the PDFs of the July-October precipitation anomalies (%) for the ALL, NAT, and noCS runs, respectively, as shown in Figure 1. The solid curves indicate the PDFs with the bias corrections (with the best estimates of the scaling factors) according to the precipitation responses to (a) ANSG, (b) ENSO, and (c) ANSG + ENSO. (d) Solid curves show the PDF estimates with the neutral ANSG + ENSO. Acknowledgements We thank Oliver Angélil who found the errors in the GHGs concentrations. This work was supported by the Program for Risk Information on Climate Change (SOUSEI program) and Grant-in-Aid 26281013 from the Ministry of Education, Culture, Sports, Science and Technology of Japan. Earth Simulator and NEC SX (NIES) were utilized for the simulations. We have no conflict of interest.

    DOI: 10.1002/asl.725

  • 21. A persistent Japanese heat wave in early August 2015: Roles of natural variability and human-induced warming Reviewed International journal

    Chiharu Takahashi, Masahiro Watanabe, Hideo Shiogama, Yukiko Imada, Masato Mori

    Bulletin of the American Meteorological Society   97 ( 12 )   S107 - S112   2016.12

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    The persistent Japanese heat wave that occurred in early August 2015 was mainly attributed to intraseasonal disturbances including tropical cyclones. Anthropogenic warming contributed to an increase in the probability of occurrence.

    DOI: 10.1175/BAMS-D-16-0157.1

  • Attributing Historical Changes in Probabilities of Record-Breaking Daily Temperature and Precipitation Extreme Events Reviewed International journal

    Hideo Shiogama, Yukiko Imada, Masato Mori, Ryo Mizuta, Daithi Stone, Kohei Yoshida, Osamu Arakawa, Mikiko Ikeda, Chiharu Takahashi, Miki Arai, Masayoshi Ishii, Masahiro Watanabe, Masahide Kimoto

    SOLA   12   225 - 231   2016.12

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    We describe two unprecedented large (100-member), longterm (61-year) ensembles based on MRI-AGCM3.2, which were driven by historical and non-warming climate forcing. These ensembles comprise the "Database for Policy Decision making for Future climate change (d4PDF)". We compare these ensembles to large ensembles based on another climate model, as well as to observed data, to investigate the influence of anthropogenic activities on historical changes in the numbers of record-breaking events, including: the annual coldest daily minimum temperature (TNn), the annual warmest daily maximum temperature (TXx) and the annual most intense daily precipitation event (Rx1day). These two climate model ensembles indicate that human activity has already had statistically significant impacts on the number of record-breaking extreme events worldwide mainly in the Northern Hemisphere land. Specifically, human activities have altered the likelihood that a wider area globally would suffer record-breaking TNn, TXx and Rx1day events than that observed over the 2001-2010 period by a factor of at least 0.6, 5.4 and 1.3, respectively. However, we also find that the estimated spatial patterns and amplitudes of anthropogenic impacts on the probabilities of record-breaking events are sensitive to the climate model and/or natural-world boundary conditions used in the attribution studies.

    DOI: 10.2151/sola.2016-045

  • Error and Energy Budget Analysis of a Nonhydrostatic Stretched-Grid Global Atmospheric Model Reviewed International journal

    Uchida, Junya, Mori, Masato, Nakamura, Hisashi, Satoh, Masaki, Suzuki, Kentaroh, Nakajima, Teruyuki

    MONTHLY WEATHER REVIEW   144 ( 4 )   1423 - 1447   2016.4

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    A nonhydrostatic stretched-grid (SG) model is used to analyze the large-scale errors generated by stretching horizontal grids and their influence on a region of interest. Simulations by a fully compressible, nonhydrostatic global atmospheric model, the Nonhydrostatic Icosahedral Atmospheric Model (NICAM), and its SG regional model, stretched-NICAM, were performed for the months of March, April, and May of 2011 using various resolutions and stretching factors. A comparison of week-long accumulative precipitation amounts between the Tropical Rainfall Measuring Mission (TRMM) satellite data and the quasi-uniform and SG simulations showed that a stretched run better represents storms and associated precipitation because the errors generated in the outer regions with coarser grid spacing do not significantly affect the inner domain centered at the focal point. For season-long simulations, in one particular set of stretched runs with the focal point located in the eastern United States, the artificial suppression of baroclinic development of midlatitude eddies in the Southern Hemisphere weakened the eddy-driven polar-front jet (PFJ), which yielded a cold bias at mid- to high latitudes. However, in the Northern Hemisphere, in contrast, the aforementioned changes are less apparent. Therefore, for the SG runs, the mean temperature was maintained at the region of interest, and an increased amount of moderate to heavy precipitation, which is also frequently found in the TRMM data, was observed; thus, the benefits of increased resolution were realized. However, careful attention must be given when applying the SG model because a regional climate response to the change in the large-scale circulations may not be fully accounted for.

    DOI: 10.1175/MWR-D-15-0271.1

  • Predictability of Two Types of El Nino Assessed Using an Extended Seasonal Prediction System by MIROC Reviewed International journal

    Yukiko Imada, Hiroaki Tatebe, Masayoshi Ishii, Yoshimitsu Chikamoto, Masato Mori, Miki Arai, Masahiro Watanabe, Masahide Kimoto

    MONTHLY WEATHER REVIEW   143 ( 11 )   4597 - 4617   2015.11

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    Predictability of El Nino-Southern Oscillation (ENSO) is examined using ensemble hindcasts made with a seasonal prediction system based on the atmosphere and ocean general circulation model, the Model for Interdisciplinary Research on Climate, version 5 (MIROC5). Particular attention is paid to differences in predictive skill in terms of the prediction error for two prominent types of El Nino: the conventional eastern Pacific (EP) El Nino and the central Pacific (CP) El Nino, the latter having a maximum warming around the date line. Although the system adopts ocean anomaly assimilation for the initialization process, it maintains a significant ability to predict ENSO with a lead time of more than half a year. This is partly due to the fact that the system is little affected by the spring prediction barrier, because increases in the error have little dependence on the thermocline variability. Composite analyses of each type of El Nino reveal that, compared to EP El Ninos, the ability to predict CP El Ninos is limited and has a shorter lead time. This is because CP El Ninos have relatively small amplitudes, and thus they are more affected by atmospheric noise; this prevents development of oceanic signals that can be used for prediction.

    DOI: 10.1175/MWR-D-15-0007.1

  • Attribution of the June-July 2013 Heat Wave in the Southwestern United States Reviewed International journal

    Hideo Shiogama, Masahiro Watanabe, Yukiko Imada, Masato Mori, Youichi Kamae, Masayoshi Ishii, Masahide Kimoto

    SOLA   10   122 - 126   2014.10

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    A severe heat wave occurred in the southwestern United States (US) during June and July 2013. To investigate the effects of natural variability and anthropogenic climate change on this event, we generated large ensemble simulations of possible weather using the MIROC5A climate model forced by "historical external forcing agents, sea surface temperature (SST) observations and sea ice (SIC) observations" both with and without human influence. It was suggested that both the anthropogenic warming and an atmospheric circulation regime related to the natural variability of SST and SIC made the heat wave event more likely. On the other hand, no significant human influence was found in atmospheric circulation patterns. These results were robust for two different estimates of anthropogenic signals on SST and SIC.

    DOI: 10.2151/sola.2014-025

  • Error Sensitivity to Initial Climate States in Pacific Decadal Hindcasts Reviewed International journal

    Takashi Mochizuki, Masahide Kimoto, Yoshimitsu Chikamoto, Masato Mori, Masahiro Watanabe, Masayoshi Ishii

    SOLA   10   39 - 44   2014.10

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    We perform decadal hindcast experiments with initialization every year and assess sensitivity of the hindcasted errors to the errors in the initial climate states. The hindcasted sea surface temperature (SST) over the extratropical North Pacific shows significant impacts of initialization, yet the hindcasted indices of the Pacific decadal variability usually suffer from limited predictability. Our sensitivity analyses reveal that, in the decadal SST hindcasts over the extratropical North Pacific, the annual-to-decadal errors of the Aleutian Low fluctuation before the time of starting hindcast experiments work as a major source of uncertainty through delayed responses of the ocean. As we directly assimilate only the ocean states to the atmosphere-ocean coupled model in initialization, the Aleutian Low fluctuation in the assimilation exhibits large errors even though the SST is well correlated with the observation. These assimilation errors in the Aleutian Low fluctuation are primarily due to the distorted responses of the extratropical atmosphere to the tropical SST changes in the model. A close examination indicates that the observed and assimilated Aleutian Lows are sensitive to the eastern and central equatorial SSTs, respectively. Toward further reducing uncertainty in the Pacific decadal hindcasts, therefore, it should be an effective way to raise quality of initial conditions for the extratropical atmosphere and the tropical atmosphere-ocean coupling.

    DOI: 10.2151/sola.2014-009

  • THE CONTRIBUTION OF ANTHROPOGENIC FORCING TO THE JAPANESE HEAT WAVES OF 2013 Reviewed International journal

    Yukiko Imada, Hideo Shiogama, Masahiro Watanabe, Masato Mori, Masayoshi Ishii, Masahide Kimoto

    BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY   95 ( 9 )   S52 - S54   2014.9

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    Anthropogenic climate change played a significant role in increasing the probability of events such as the heat wave in Japan in 2013.

  • Tropical Cyclone Tracking Using a Neighbor Enclosed Area Tracking Algorithm Reviewed International journal

    Yuya Satake, Masaru Inatsu, Masato Mori, Akira Hasegawa

    MONTHLY WEATHER REVIEW   141 ( 10 )   3539 - 3555   2013.10

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    Tropical cyclone (TC) tracking is essential for calculating TC statistics from gridded datasets. A new method for TC tracking is presented here using neighbor enclosed area tracking (NEAT), which is based on the temporal overlap of enclosed areas above a vorticity threshold and differs from the widely used neighbor point tracking (NPT) method. The parameters of cyclone intensity, vertical-shear, and warm-core criteria were intensively tuned for NEAT and NPT. When these criteria were optimized for the typhoon tracks observed in the western North Pacific based on the Japanese 25-yr Reanalysis Project (JRA-25)/Japan Meteorological Agency (JMA) Climate Data Assimilation System (JCDAS) dataset, the NEAT and NPT algorithms captured approximately 85% of typhoons with little qualitative distortion in the spatial distribution and temporal variability of the TC track density. The grid system dependency of the algorithms was tested by applying NEAT and NPT to a high-resolution general circulation model output. The method presented here can also provide realistic statistics on the TC size, the extratropical transition timing, and the meridional heat transport.

    DOI: 10.1175/MWR-D-12-00092.1

  • Contribution of atmospheric circulation change to the 2012 heavy rainfall in southern Japan Reviewed International journal

    Yukiko Imada, Hideo Shiogama, Masahiro Watanabe, Masato Mori, Masayoshi Ishii, Masahide KimotoYukiko Imada, Masahiro Watanabe, Masato Mori, Masahide Kimoto, Hideo Shiogama, Masayoshi Ishii

    Bulletin of the American Meteorological Society [in “Explaining Extreme Events of 2012 from a Climate Perspective”]   94 ( 9 )   S52 - S54   2013.9

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    Contribution of atmospheric circulation change to the 2012 heavy rainfall in southern Japan

  • Event Attribution of the August 2010 Russian Heat Wave Reviewed International journal

    Masahiro Watanabe, Hideo Shiogama, Yukiko Imada, Masato Mori, Masayoshi Ishii, Masahide Kimoto

    SOLA   9   65 - 68   2013.9

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    An extreme heat wave hit western Russia in the summer of 2010. To investigate the contribution of anthropogenic climate change to this event, 100-member ensembles of atmospheric general circulation model (AGCM) experiments, with and without possible human-induced changes in sea surface temperature (SST) and sea ice, were generated. The AGCM can reproduce monthly surface air temperature (SAT) anomalies for the past 30 years over the continental area, indicating a significant influence of the anomalous boundary conditions on the surface climate variability. While the ensemble average does not capture the extremely high SAT anomaly over western Russia observed in August 2010, the ensemble covers the anomaly with the probability of occurrence at 3.3%. Without the anthropogenic change in SST and sea ice, the ensemble fails to capture the observed SAT anomaly, reducing the probability of occurrence to 0.6%. The atmospheric response to the tropical precipitation change associated with anthropogenic SST increase leads to warming over Eurasia through northward temperature advection, consistent with the observed upward SAT trend. Drying of the land surface in spring may also have favored the summer warming over western Russia.

    DOI: 10.2151/sola.2013-015

  • Superrotation and Nonlinear Hadley Circulation Response to Zonally Asymmetric Sea Surface Temperature in an Aquaplanet GCM Reviewed International journal

    Masato Mori, Masahiro Watanabe, Masahide Kimoto

    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN   91A   269 - 291   2013.9

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    The responses of the equatorial zonal wind and the Hadley circulation to the equatorial zonal wavenumber one sea surface temperature (SST) anomaly, T-s*, are examined in an atmospheric general circulation model (AGCM) with an aquaplanet condition. The Hadley cell is weakened as the magnitude of T-s* increases, balancing with a decrease in the zonal-mean diabatic heating over the tropics. The decrease of heating reflects a nonlinear relationship between precipitation and SST; deep convection, such as a super cloud cluster, is significantly suppressed over cold T-s*, whereas is slightly enhanced over warm T-s*. The effective suppression of deep convection is accomplished by the stable boundary layer and the dry subsidence anomaly associated with the Walker cell which is excited by the SST anomaly. And the decreased convection acts to further reinforce the subsidence via thermodynamic balance. Therefore, this positive feedback between large-scale circulation and deep convection determines the nonlinear relationship and controls the strength of the Hadley cell.
    In terms of the energetics of the tropical circulation, the Hadley cell has to be weakened to compensate for the lack of energy supply caused by an increase of tropical radiative cooling due to the effective suppression of deep convection over cold T-s*.
    We compared the results of our AGCM with that of other 15 aquaplanet AGCMs integrated with the same SST distribution. While the Hadley cell is weakened in all AGCMs when T-s* is added to the zonal uniform SST, there is a large diversity in the strength. This suggests that the difference in the physical parameterization causes a different sensitivity of the Hadley cell response to zonally asymmetric SST. The magnitude of weakening is approximately proportional to the decreased (increased) amount of the deep convective precipitation (the radiative cooling) over the tropics. This strong relationship suggests that the positive feedback also works in other AGCMs. It is considered that the feedback is also important for understanding the formation of a real tropical climate.

    DOI: 10.2151/jmsj.2013-A10

  • EXPLAINING EXTREME EVENTS OF 2012 FROM A CLIMATE PERSPECTIVE Reviewed International journal

    Thomas C. Peterson, Lisa V. Alexander, Myles R. Allen, Juan A. Anel, David Barriopedro, Mitchell T. Black, Trevor Carey-Smith, Rodrigo Castillo, Julien Cattiaux, Xiaolong Chen, Xianyan Chen, Matthieu Chevallier, Nikolaos Christidis, Andrew Ciavarella, Hylke de Vries, Sam M. Dean, Kirsten Deans, Noah S. Diffenbaugh, Francisco Doblas-Reyes, Markus G. Donat, Buwen Dong, Gary Eilerts, Chris Funk, Gideon Galu, Ricardo Garcia-Herrera, Agathe Germe, Stephen Gill, Luis Gimeno, Virginie Guemas, Stephanie C. Herring, Andrew Hoell, Martin P. Hoerling, Chris Huntingford, Greg Husak, Yukiko Imada, Masayoshi Ishii, David J. Karoly, Masahide Kimoto, Andrew D. King, Thomas R. Knutson, Sophie C. Lewis, Renping Lin, Bradfield Lyon, Neil Massey, Edoardo Mazza, Joel Michaelsen, James Mollard, Masato Mori, Philip W. Mote, Raquel Nieto, Friederike E. L. Otto, Joseph Park, Sarah E. Perkins, Suzanne Rosier, James Rowland, David E. Rupp, David Salas y Melia, Martin Scherer, Hideo Shiogama, Shraddhanand Shukla, Fengfei Song, Sarah Sparrow, Peter A. Scott, Rowan Sutton, William Sweet, Simon F. B. Tett, Ricardo Machado Trigo, Geert Jan van Oldenborgh, Rudolf van Westrhenen, James Verdin, Masahiro Watanabe, Andrew T. Wittenberg, Tim Woollings, Pascal Yiou, Fanrong Zeng, Chris Zervas, Rong Zhang, Tianjun Zhou

    BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY   94 ( 9 )   S1 - S74   2013.9

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    DOI: 10.1175/BAMS-D-13-00085.1

  • Control of Decadal and Bidecadal Climate Variability in the Tropical Pacific by the Off-Equatorial South Pacific Ocean Reviewed International journal

    Hiroaki Tatebe, Yukiko Imada, Masato Mori, Masahide Kimoto, Hiroyasu Hasumi

    JOURNAL OF CLIMATE   26 ( 17 )   6524 - 6534   2013.9

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    Delayed negative feedback processes determining intrinsic decadal and bidecadal time scales for the tropical variability in the Pacific are investigated based on climate model experiments. By comparing a control run driven by preindustrial forcing and partial blocking runs driven by the same forcing but with ocean temperature and salinity restored to climatology in selected regions, subsurface oceanic signals of South Pacific origin are shown to precede SST variability in the Nino-3.4 region. Using a linear reduced-gravity ocean model driven only by wind stress changes and an offline tracer model, oceanic wave adjustment triggered by changes of wind stress curl in the South Pacific extratropics is suggested to be essential for the decadal component of the equatorial SST, while slower isopycnal advection of subsurface temperature anomalies from the formation region of South Pacific Eastern Subtropical Mode Water controls the bidecadal component. The intrinsic time scales of the tropical variability are regulated by simple linear ocean dynamics.

    DOI: 10.1175/JCLI-D-12-00137.1

  • Hindcast Prediction and Near-Future Projection of Tropical Cyclone Activity over the Western North Pacific Using CMIP5 Near-Term Experiments with MIROC Reviewed International journal

    Masato Mori, Masahide Kimoto, Masayoshi Ishii, Satoru Yokoi, Takashi Mochizuki, Yoshimitsu Chikamoto, Masahiro Watanabe, Toru Nozawa, Hiroaki Tatebe, Takashi T. Sakamoto, Yoshiki Komuro, Yukiko Imada, Hiroshi Koyama

    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN   91 ( 4 )   431 - 452   2013.8

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    In line with the experimental design for near-term climate prediction toward the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, we perform ensembles of initialized decadal hindcast and near-future projection using three versions of the coupled atmosphere ocean model MIROC. In the present study, we explore interannual and multiyear predictability of tropical cyclone (TC) activity in the western North Pacific (WNP) using the initialized hindcasts and examine global warming impacts on TC activity in the near-future on the basis of near-future projections up to 2035.
    The hindcasts of year-to-year variation in TC number capture the observed values reasonably well. Moreover, interannual variability of TC genesis and occurrence frequency associated with the El Nino Southern Oscillation are found to be predictable, mainly through better prediction of sea surface temperature (SST) and large-scale vorticity anomalies in the lower troposphere. These results indicate that the models can reproduce the major basic mechanisms that link TC genesis with large-scale circulation. Skillful prediction of TC number is likely difficult on multiyear timescales, at least based on our hindcasts, but through initializations, the three-year-mean hindcasts from 1998 onward reasonably capture observed major characteristics of TC activity associated with Pacific climate shift during the late 1990s.
    Near-future projections (2016-2035) suggest significant reductions (approximately 14%) in TC number, particularly over the western part of the WNP, even under scenarios in which projected global warming is less prominent than that at the end of this century. This reduction is likely due to the suppression of large-scale lower tropospheric vorticity and relative humidity and the enhancement of vertical wind shear. The projected SST exhibits a more pronounced warming over the eastern tropical Pacific than over the western region and accompanies the weakening of Walker circulation via redistribution of tropical convection activity, which appears to be responsible for the change in the large-scale fields in the WNP.

    DOI: 10.2151/jmsj.2013-402

  • An event attribution of the 2010 drought in the South Amazon region using the MIROC5 model Reviewed International journal

    Hideo Shiogama, Masahiro Watanabe, Yukiko Imada, Masato Mori, Masayoshi Ishii, Masahide Kimoto

    Atmospheric Science Letters   14 ( 3 )   170 - 175   2013.7

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    We produced 100-member event attribution ensembles during 2009-2012 under all forcing conditions and in two different counterfactual worlds without anthropogenic forcing (mainly greenhouse gases and aerosols) and without aerosol emission changes using the MIROC5 atmospheric general circulation model. It seemed that both human influences and the sea surface temperature (SST) natural variability increased probabilities of the 2010 severe drought in the South Amazon region, and that changes in aerosols emissions had little effect on the drought. It should be noted that our assessments were sensitive to bias corrections according to the relationships between the SST natural variability and precipitation. © 2013 The Authors.

    DOI: 10.1002/asl2.435

  • Response of extratropical cyclone activity to the Kuroshio large meander in northern winter Reviewed International journal

    Masamitsu Hayasaki, Ryuichi Kawamura, Masato Mori, Masahiro Watanabe

    GEOPHYSICAL RESEARCH LETTERS   40 ( 11 )   2851 - 2855   2013.6

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    We examined possible responses of cyclone activities to the bimodal path states of the Kuroshio Current [i.e., large meander (LM) and non-LM (NLM)] by using the long-term reanalysis data and the 20th century hindcast experiment of a high-resolution atmosphere-ocean coupled model. Compared with a seasonal mean cyclone track frequency for the LM and NLM periods, a primary cyclone track shifts southward in association with the meander of Kuroshio Current. Composite analyses of the hindcast experiment showed remarkable atmospheric responses accompanying the Kuroshio LM. The Kuroshio LM causes a decrease in latent heat flux in the south of Japan and a southward shift of the near-surface baroclinic zone. Distinctive decreases in thermodynamic fluxes inhibit the rapid development of cyclones in the meander region, eventually inducing positive sea level pressure anomalies downstream from that region.

    DOI: 10.1002/grl.50546

  • An overview of decadal climate predictability in a multi-model ensemble by climate model MIROC Reviewed International journal

    Yoshimitsu Chikamoto, Masahide Kimoto, Masayoshi Ishii, Takashi Mochizuki, Takashi T. Sakamoto, Hiroaki Tatebe, Yoshiki Komuro, Masahiro Watanabe, Toru Nozawa, Hideo Shiogama, Masato Mori, Sayaka Yasunaka, Yukiko Imada

    Climate Dynamics   40 ( 5-6 )   1201 - 1222   2013.5

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    Decadal climate predictability is examined in hindcast experiments by a multi-model ensemble using three versions of the coupled atmosphere-ocean model MIROC. In these hindcast experiments, initial conditions are obtained from an anomaly assimilation procedure using the observed oceanic temperature and salinity with prescribed natural and anthropogenic forcings on the basis of the historical data and future emission scenarios in the Intergovernmental Panel of Climate Change. Results of the multi-model ensemble in our hindcast experiments show that predictability of surface air temperature (SAT) anomalies on decadal timescales mostly originates from externally forced variability. Although the predictable component of internally generated variability has considerably smaller SAT variance than that of externally forced variability, ocean subsurface temperature variability has predictive skills over almost a decade, particularly in the North Pacific and the North Atlantic where dominant signals associated with Pacific decadal oscillation (PDO) and the Atlantic multidecadal oscillation (AMO) are observed. Initialization enhances the predictive skills of AMO and PDO indices and slightly improves those of global mean temperature anomalies. Improvement of these predictive skills in the multi-model ensemble is higher than that in a single-model ensemble. © 2012 The Author(s).

    DOI: 10.1007/s00382-012-1351-y

  • MIROC4h-A New High-Resolution Atmosphere-Ocean Coupled General Circulation Model Reviewed International journal

    Takashi T. Sakamoto, Yoshiki Komuro, Teruyuki Nishimura, Masayoshi Ishii, Hiroaki Tatebe, Hideo Shiogama, Akira Hasegawa, Takahiro Toyoda, Masato Mori, Tatsuo Suzuki, Yukiko Imada, Toru Nozawa, Kumiko Takata, Takashi Mochizuki, Koji Ogochi, Seita Emori, Hiroyasu Hasumi, Masahide Kimoto

    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN   90 ( 3 )   325 - 359   2012.6

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    A new high-resolution atmosphere-ocean coupled general circulation model named MIROC4h has been developed, and its performance in a 120-year control experiment (including a 50-year spin-up) under the present conditions (the year 1950) is examined. The results of the control experiment by MIROC4h are compared with simulations of preindustrial conditions carried out for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) using the previous high- and medium-resolution versions of the model, called MIROC3h and MIROC3m, respectively. A major change in MIROC4h is a doubling of the resolution of the atmospheric component to 0.5625 degrees, compared to 1.125 degrees for MIROC3h. The oceanic components of MIROC4h and MIROC3h are eddy-permitting, with a horizontal resolution of 0.28125 degrees (zonal) x 0.1875 degrees (meridional). In MIROC3m, the horizontal resolution is 2.8125 degrees for the atmospheric component and 1.40625 degrees (zonal) x 0.56 degrees-1.4 degrees (meridional) for the ocean component.
    Compared with MIROC3h and MIROC3m, many improvements have been achieved; for example, errors in the surface air temperature and sea surface temperature are smaller, there is less drift of the ocean water temperature in the subsurface-deep ocean, and the frequency of heavy rain is comparable to observations. The fine horizontal resolution in the atmosphere makes orographic wind and its effects on the ocean more realistic than those of the former models, and the treatment of coastal upwelling motion in the ocean has been improved. Phenomena in the atmosphere and ocean related to the El Nino and southern oscillation are now closer to observations than was obtained by MIROC3h and MIROC3m. The effective climate sensitivity for CO2 doubling is calculated to be about 5.7 K, which is much larger than the value obtained using the IPCC AR4 models, and is mainly due to a decrease in the low-level clouds at low latitudes.

    DOI: 10.2151/jmsj.2012-301

  • Decadal Prediction Using a Recent Series of MIROC Global Climate Models Reviewed International journal

    Takashi Mochizuki, Yoshimitsu Chikamoto, Masahide Kimoto, Masayoshi Ishii, Hiroaki Tatebe, Yoshiki Komuro, Takashi T. Sakamoto, Masahiro Watanabe, Masato Mori

    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN   90A   373 - 383   2012.2

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    In line with the experimental design for near-term climate prediction toward the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC-AR5) and the Coupled Model Intercomparison Project Phase 5 (CMIP5), we perform ensembles of initialized decadal hindcast experiments using two recent versions of the Model for Interdisciplinary Research On Climate (MIROC): MIROC4h (T213L56 AGCM and 1/6-1/4 deg. 48 level OGCM) and MIROC5 (T85L40 AGCM and 0.56-1.4 deg. 50 level OGCM). We analyze sets of 10-year-long 9-ensemble hindcasts (3 members by MIROC4h and 6 members by MIROC5) with initialization every five years after 1961 and explore the predictability of decadal climate changes.
    The most predictable variation on decadal timescales is the global warming signal due to the favorable response of the models to external forcing. The results of these initialized hindcast experiments using MIROC5 validate our ability to enhance decadal predictability primarily through the initialization, particularly of the Pacific Decadal Oscillation (PDO) for a few years and of the Atlantic Multidecadal Oscillation (AMO) for almost a decade. The initialization has large impacts on the upper ocean temperature hindcasts over the mid- and high latitudes of the North Pacific and the high latitudes of the North Atlantic, where the PDO and AMO signals are observed to be strongest. In contribution to process and assessment studies in IPCC-AR5 and CMIP5, further analysis of our hindcast data (and near-term prediction data) using MIROC4h and MIROC5 is worthwhile. We note that the initialized hindcasts using MIROC4h have predictive skill inferior to the MIROC5 results and that at this stage, fully significant discussions may not be possible due to the small number of ensembles with limited computational resources.

    DOI: 10.2151/jmsj.2012-A22

  • The Initialization of the MIROC Climate Models with Hydrographic Data Assimilation for Decadal Prediction Reviewed International journal

    Hiroaki Tatebe, Masayoshi Ishii, Takashi Mochizuki, Yoshimitsu Chikamoto, Takashi T. Sakamoto, Yoshiki Komuro, Masato Mori, Sayaka Yasunaka, Masahiro Watanabe, Koji Ogochi, Tatsuo Suzuki, Teruyuki Nishimura, Masahide Kimoto

    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN   90A   275 - 294   2012.2

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    This paper documents the procedure of ocean data assimilation that initializes the climate models MIROC3m, MIROC4h, and MIROC5 for decadal climate predictions following the CMIP5 protocol, and summarizes the performance of the climate models using this data assimilation. Only anomalies of observed ocean hydrographic data are assimilated using the incremental analysis update method in order to prevent model climate drifts during predictions. In the case of MIROC4h, which has an eddy-permitting ocean model, a spatial smoother is used in calculating analysis increments so that oceanic mesoscale eddies cannot be damped by observational constraints and that they are generated and decay physically in response to the assimilated background state. Globally, the decadal-scale variations of ocean temperatures in the assimilation runs are highly correlated with the observations. Variations of surface air temperature over oceans are also consistent with the observations, but this is not the case in some regions over continents. Atmospheric responses to the SST variations corresponding to the Pacific Decadal Oscillations and the Atlantic Multi-decadal Oscillation are better represented in MIROC4h and MIROC5 than in MIROC3m. The high resolution of MIROC4h and new cloud parameterizations in MIROC5 may contribute to this improvement. Root-mean-squared amplitudes of sea surface height variations associated with oceanic eddies (hereafter, eddy activity) are not suppressed undesirably in the MIROC4h assimilation run and these are comparable with those in the uninitialized runs. In the Kuroshio-Oyashio confluence zone, eddy activity is modulated on a decadal timescale. This modulation is reasonably represented in the assimilation run compared with the observations. in the hindcast experiments, significant decadal prediction skills are found for the North Atlantic, the subtropical North Pacific, and the Indian Ocean. The decadal climate predictions are expected to contribute to the IPCC AR5 and political decision-making for the coming decades.

    DOI: 10.2151/jmsj.2012-A14

  • Predictability of a Stepwise Shift in Pacific Climate during the Late 1990s in Hindcast Experiments Using MIROC Reviewed International journal

    Yoshimitsu Chikamoto, Masahide Kimoto, Masayoshi Ishii, Masahiro Watanabe, Toru Nozawa, Takashi Mochizuki, Hiroaki Tatebe, Takashi T. Sakamoto, Yoshiki Komuro, Hideo Shiogama, Masato Mori, Sayaka Yasunaka, Yukiko Imada, Hiroshi Koyama, Masato Nozu, Fei-fei Jin

    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN   90A   1 - 21   2012.2

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    Sea surface temperature (SST) predictability in the Pacific on decadal timescales is examined in hindcast experiments using the coupled atmosphere-ocean model MIROC with low, medium, and high resolutions. In these hindcast experiments, initial conditions are obtained from an anomaly assimilation procedure using the observed oceanic temperature and salinity while prescribing natural and anthropogenic forcing based on the IPCC concentration scenarios. Our hindcast experiments show the predictability of SST in the western subtropical Pacific, the Indian Ocean, and the tropics to the North Atlantic. Previous studies have examined the SST predictability in the Indian Ocean and the Atlantic, but SST predictability in the western subtropical Pacific has not been evaluated. In the western Pacific, the observed SST anomalies in the subtropics of both hemispheres increased rapidly from the early 1990s to the early 2000s. While this SST warming in the western subtropical Pacific is partly explained by global warming signals, the predictions of our model initialized in 1995 or 1996 tend to simulate the pattern of the SST increase and the associated precipitation changes. This large climate change around the late 1990s may be related to phenomena such as the recent increase in the typhoon frequency in Taiwan and the weakened East Asian monsoon reported by recent studies.

    DOI: 10.2151/jmsj.2012-A01

  • Impact of the Assimilation of Sea Ice Concentration Data on an Atmosphere-Ocean-Sea Ice Coupled Simulation of the Arctic Ocean Climate Reviewed International journal

    Takahiro Toyoda, Toshiyuki Awaji, Nozomi Sugiura, Shuhei Masuda, Hiromichi Igarashi, Yuji Sasaki, Yoshihisa Hiyoshi, Yoichi Ishikawa, Takashi Mochizuki, Takashi T. Sakamoto, Hiroaki Tatebe, Yoshiki Komuro, Tatsuo Suzuki, Teruyuki Nishimura, Masato Mori, Yoshimitsu Chikamoto, Sayaka Yasunaka, Yukiko Imada, Miki Arai, Masahiro Watanabe, Hideo Shiogama, Toru Nozawa, Akira Hasegawa, Masayoshi Ishii, Masahide Kimoto

    SOLA   7   37 - 40   2011.7

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    We have investigated the effects of assimilating sea ice concentration (SIC) data on a simulation of Arctic Ocean climate using an atmosphere-ocean-sea ice coupled model. Our results show that the normal overestimation of summertime SIC in the East Siberian Sea and the Beaufort Sea in simulations without sea-ice data input can be greatly reduced by assimilating sea-ice data and that this improvement is also evident in a following hindcast experiment for 3-4 years after the initialization of the assimilation. In the hindcast experiment, enhanced heat storage in both sea ice and in the ocean surface layer plays a central role in improving the accuracy of the sea ice distribution, particularly in summer. Our detailed investigation suggests that the ice-albedo feedback and the feedback associated with the atmospheric pressure pattern generated by the improved estimation of SIC work more effectively to retain the heat signal after initialization for a coupled atmosphere-ocean-sea ice system prediction. In addition, comparison with field observations confirms that the model fails to produce a realistic feedback loop, which is (presumably) due to inadequacies in both the ice-cloud feedback model and the feedback via the Beaufort Gyre circulation. Further development of coupled models is thus required to better define Arctic Ocean climate processes and to improve the accuracy of their predictions.

    DOI: 10.2151/sola.2011-010

  • Pacific decadal oscillation hindcasts relevant to near-term climate prediction Reviewed International journal

    Takashi Mochizuki, Masayoshi Ishii, Masahide Kimoto, Yoshimitsu Chikamoto, Masahiro Watanabe, Toru Nozawa, Takashi T. Sakamoto, Hideo Shiogama, Toshiyuki Awaji, Nozomi Sugiura, Takahiro Toyoda, Sayaka Yasunaka, Hiroaki Tatebe, Masato Mori

    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA   107 ( 5 )   1833 - 1837   2010.2

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    Decadal-scale climate variations over the Pacific Ocean and its surroundings are strongly related to the so-called Pacific decadal oscillation (PDO) which is coherent with wintertime climate over North America and Asian monsoon, and have important impacts on marine ecosystems and fisheries. In a near-term climate prediction covering the period up to 2030, we require knowledge of the future state of internal variations in the climate system such as the PDO as well as the global warming signal. We perform sets of ensemble hindcast and forecast experiments using a coupled atmosphere-ocean climate model to examine the predictability of internal variations on decadal timescales, in addition to the response to external forcing due to changes in concentrations of greenhouse gases and aerosols, volcanic activity, and solar cycle variations. Our results highlight that an initialization of the upper-ocean state using historical observations is effective for successful hindcasts of the PDO and has a great impact on future predictions. Ensemble hindcasts for the 20th century demonstrate a predictive skill in the upper-ocean temperature over almost a decade, particularly around the Kuroshio-Oyashio extension (KOE) and subtropical oceanic frontal regions where the PDO signals are observed strongest. A negative tendency of the predicted PDO phase in the coming decade will enhance the rising trend in surface air-temperature (SAT) over east Asia and over the KOE region, and suppress it along the west coasts of North and South America and over the equatorial Pacific. This suppression will contribute to a slowing down of the global-mean SAT rise.

    DOI: 10.1073/pnas.0906531107

  • Growth and triggering mechanisms of the PNA: A MJO-PNA coherence Reviewed International journal

    Masato Mori, Masahiro Watanabe

    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN   86 ( 1 )   213 - 236   2008.2

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    A prominent mode of low-frequency variability in the northern extratropical winter known as the Pacific/North American (PNA) teleconnection pattern prevails not only on seasonal but also on intraseasonal timescales. In this study, processes governing the intraseasonal PNA are investigated using daily fields during 1957-2002. The results of the vorticity budget analysis illustrate that the positive phase of the PNA tends to grow by linear processes such as the barotropic energy conversion from the zonally asymmetric climatological flow. For the negative phase of the PNA, nonlinear low-frequency vorticity advection is as important as the linear processes.
    Composite life cycle of the PNA shows that at 9 days before the peak a pronounced wave train was observed along the Asian jet stream and it eventually developed to the PNA near the jet exit region. This wave train is found to be excited by divergent winds primarily associated with anomalous convection of the Madden-Julian Oscillation (MJO). Probability density functions of the MJO calculated separately following the polarity of the PNA reveal a phase locking between the PNA and the MJO. When the active (inactive) convection associated with the MJO reaches the Bay of Bengal to the western Pacific, occurrence frequency of the negative (positive) phase of the PNA is the highest. This MJO triggering explains roughly 30% of the total PNA events, suggesting that, even though the PNA may be inherent to the extratropical atmosphere, a specific tropical forcing is of importance to realize the PNA as dominant mode.

    DOI: 10.2151/jmsj.86.213

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Books

  • 北極域の研究―その現状と将来構想

    北極環境研究コンソーシアム長期構想編集委員会 編(Role:Joint author)

    2024.3 

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    Language:Japanese   Book type:Scholarly book

MISC

  • Event Attribution(イベントアトリビューション)

    森 正人, 今田 由紀子, 塩竈 秀夫, 渡部 雅浩

    天気   2013.5

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)  

  • 2018年秋季「極域・寒冷域研究連絡会」の報告 : 北極海の海氷減少の中緯度気候への影響は本当か?

    西井 和晃, 中村 哲, 森 正人

    天気   2019.5

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    Language:Japanese  

  • 研究集会「異常気象と気候システム変動のメカニズムと予測可能性」の報告

    榎本 剛, 水田 亮, 森 正人, 宮坂 貴文, 遠藤 洋和, 松枝 未遠

    天気   2014.4

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    Language:Japanese  

  • 2005年12月の「北極振動」の励起と予測可能性 (2005/06年 日本の寒冬・豪雪) -- (寒冬・豪雪の長期予報及び予測可能性)

    森 正人, 小山 博司, 渡部 雅浩

    気象研究ノ-ト   2007.11

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    Language:Japanese  

Professional Memberships

Committee Memberships

  • 気象庁異常気象分析作業部会   委員   Domestic

    2017.10 - Present   

  • 日本気象学会第40 期役員選挙管理委員会   委員   Domestic

    2017.9 - 2018.4   

Academic Activities

  • The Scientific Online Letters on the Atmosphere (SOLA) International contribution

    Role(s): Peer review

    2022.6 - Present

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    Type:Peer review 

  • 第7回国際北極研究シンポジウム(ISAR-7)組織委員会 委員 International contribution

    Role(s): Planning, management, etc.

    The Seventh International Symposium on Arctic Research (ISAR-7)  ( Japan ) 2020.9 - 2023.3

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    Type:Competition, symposium, etc. 

  • 日本気象学会2019 年度春季大会 専門分科会 世話人

    日本気象学会2019 年度春季大会 専門分科会「東アジアで近年発生する極端現象に対する地球温暖化の寄与とその将来予測」  ( Japan ) 2019.10

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    Type:Competition, symposium, etc. 

  • 日本気象学会2017 年度秋季大会 専門分科会 世話人

    日本気象学会2017 年度秋季大会 専門分科会「大規模アンサンブル気候実験を用いた新しい研究の展開」  ( Japan ) 2017.10

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    Type:Competition, symposium, etc. 

  • 日本地球惑星科学連合2017 年大会 代表コンビーナ International contribution

    日本地球惑星科学連合2017 年大会「北極域の科学」  ( Japan ) 2017.5

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    Type:Competition, symposium, etc. 

  • 日本地球惑星科学連合2016 年大会 共同コンビーナ International contribution

    日本地球惑星科学連合2016 年大会「北極域の科学」  ( Japan ) 2016.5

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    Type:Competition, symposium, etc. 

  • 日本地球惑星科学連合2013 年大会 共同コンビーナ International contribution

    日本地球惑星科学連合2013 年大会「熱帯太平洋におけるマルチスケール大気海洋相互作用現象」  ( Japan ) 2013.5

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    Type:Competition, symposium, etc. 

  • 日本地球惑星科学連合2012 年大会 共同コンビーナ International contribution

    日本地球惑星科学連合2012 年大会「熱帯太平洋におけるマルチスケール大気海洋相互作用現象」  ( Japan ) 2012.5

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Research Projects

  • Extratropical climate variability and change bi-directionally interacting with the tropics and polar regions

    Grant number:24H02229  2024.4 - 2029.3

    Japan Society for the Promotion of Science・Ministry of Education, Culture, Sports, Science and Technology  Grants-in-Aid for Scientific Research  Grant-in-Aid for Transformative Research Areas (A)

    時長 宏樹, 小川 史明, 山本 絢子, 森 正人, 望月 崇, 谷本 陽一

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    Authorship:Coinvestigator(s)  Grant type:Scientific research funding

    本研究では、全球的な視点から、熱帯・極域と双方向作用する中緯度気候変動の実態を解明し、その将来変化を不確実性も含め評価することを目的とする。大気海洋結合モデル相互比較プロジェクトのマルチモデル解析、大気大循環モデルの大規模アンサンブル数値実験、および大気海洋結合モデルのペースメーカー実験等を用いて、経年から十年規模の自然変動と地球温暖化による気候変化の影響を解明し、大気-海洋相互作用や熱帯・中緯度・極域間の遠隔作用に関する物理プロセス理解の深化を目指す。

    CiNii Research

  • 文部科学省「気候変動予測先端研究プログラム」気候変動予測と気候予測シミュレーション技術の高度化(全球気候モデル)

    2022.5 - 2027.3

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    Authorship:Collaborating Investigator(s) (not designated on Grant-in-Aid) 

  • 大気渦状擾乱の極性別の振舞いを評価可能な斬新な診断法による新しい大気循環力学

    Grant number:22H01292  2022.4 - 2025.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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    Authorship:Coinvestigator(s)  Grant type:Scientific research funding

  • 北極-中緯度連に果たす大気-海洋-海氷相互作用機構の解明

    Grant number:22H01299  2022.4 - 2025.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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    Authorship:Principal investigator  Grant type:Scientific research funding

  • 木下基礎科学研究基金助成事業

    2021

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    Grant type:Donation

  • 文部科学省「北極域研究加速プロジェクト(ArCSⅡ)」気象気候の遠隔影響と予測可能性

    2020.6 - 2025.3

  • 気候変動影響評価のための日本域の異常天候ストーリーラインの構築

    Grant number:2-1904  2019.4 - 2022.3

    環境再生保全機構  環境研究総合推進費  環境研究総合推進費(環境省)

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    Authorship:Coinvestigator(s)  Grant type:Contract research

  • Climate variability and predictability in the extratropics

    Grant number:19H05703  2019 - 2023

    Japan Society for the Promotion of Science・Ministry of Education, Culture, Sports, Science and Technology  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research on Innovative Areas

    望月 崇, 森 正人, 今田 由紀子, 宮川 知己, 小坂 優

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    Authorship:Coinvestigator(s)  Grant type:Scientific research funding

    日本の地球温暖化予測研究グループとの連携の下,海洋の気候学的能動性を踏まえた中長期変動物理と予測可能性の視点から,中緯度気候について包括的な理解を目指す。そのために,温暖化予測に関わる気候シミュレーションデータを横断的に精査するとともに,機動性が高いさまざまな気候シミュレーションを併用する。高解像度や観測データとの融合という特色ある気候シミュレーションデータを活用し,変わりゆく気候のなかで中緯度気候や海洋の気候学的能動性に関係する変動物理や中長期変化傾向の解明に向けて,遠隔影響の効果も含めたグローバルな視点から取り組む。

    CiNii Research

  • 北極海氷の減少が如何にして東アジアの異常寒波を形成・増幅させるのか?

    Grant number:19H01964  2019 - 2021

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    森 正人, 西井 和晃, 小坂 優

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    Authorship:Principal investigator  Grant type:Scientific research funding

    海氷面積の急速な縮小を伴う北極域の加速度的な温暖化とは対照的に、冬季ユーラシア大陸の中緯度域では近年、異常寒波や厳冬が頻発し、北極域とは逆に寒冷化が進んでいる。観測データの解析や大気モデルを用いた感度実験により、当該地域に低温偏差をもたらす大気内部モードの発生確率が海氷減少に呼応して増加していることが明らかになってきた。しかし、海氷から大気への影響だけでなく、大気から海氷への影響も考慮した包括的なメカニズムの解明が求められている。本研究では、最新の大気海洋結合モデルによる大規模アンサンブルシミュレーションから、大気内部モードの形成・維持メカニズムやその励起・増幅機構を明らかにする。

    CiNii Research

  • 平成30年7月豪雨による災害の総合研究

    Grant number:18K19951  2018

    Japan Society for the Promotion of Science・Ministry of Education, Culture, Sports, Science and Technology  Grants-in-Aid for Scientific Research  Grant-in-Aid for Special Purposes

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    Grant type:Scientific research funding

  • 文部科学省「統合的気候モデル高度化研究プログラム」全球規模の気候変動予測と基盤的モデル開発

    2017.4 - 2022.3

  • Potential contribution of interbasin interaction to the western Pacific climate variability and tropical cyclone activity on subdecadal to decadal timescales

    Grant number:17K05661  2017.4 - 2021.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

    Mochizuki Takashi

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    Authorship:Coinvestigator(s)  Grant type:Scientific research funding

    We tried to enhance our knowledge of decadal variations in the western Pacific climate and tropical cyclone activity, focusing on interbasin interactions in the climate system. We have found a subdecadal variation that has been distinctively observed in the 2000s over the tropical Pacific, possibly related to the potential chance of heavy rainfall near Japan. By performing partial data assimilation of a global climate model, we have demonstrated that ocean temperature anomalies in the tropical and north Atlantic Oceans contribute to the distinctive fluctuations observed in the 2000s as above, while the direct contribution to modulation of the tropical cyclone activity is not significantly detected. In our decadal hindcasts with initialization, the climate model predominantly simulates a different type of fluctuations in any decade, and the resultant low predictability of the subdecadal variation in the 2000s can work to modulate the predictive skills at a lead time of several years.

    CiNii Research

  • 独立行政法人科学技術振興機構「戦略的国際科学技術協力推進事業」 JPI Climate and Belmont Forum “Climate Predictability and Inter-regional Linkages (気候予測可能性と地域間連関)” International coauthorship

    2016.9 - 2020.3

  • 文部科学省「北極域研究推進プロジェクト(ArCS)」北極気候変動予測研究

    2015.9 - 2020.3

  • 北極海海氷の減少が偏西風の蛇行をもたらすメカニズムの解明

    Grant number:15K17758  2015.4 - 2017.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Young Scientists (B)

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    Authorship:Principal investigator  Grant type:Scientific research funding

  • 文部科学省「気候変動リスク情報創生プログラム」直面する地球環境変動の予測と診断

    2012.4 - 2017.3

  • 文部科学省「21世紀気候変動予測革新プログラム」高解像度気候モデルによる近未来気候変動予測に関する研究

    2007.4 - 2012.3

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Social Activities

  • 北極圏の温暖化による遠隔気候影響

    日本気象学会 第56回夏季大学  オンライン  2022.8

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    Audience:General, Scientific, Company, Civic organization, Governmental agency

    Type:Lecture

  • 小学生用SDGs副読本「南極・北極から地球の未来を考える」

    公益財団法人 日本極地研究振興会  2021.3

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    Audience:Infants, Schoolchildren, Junior students, High school students

    Type:Other

  • 「南極・北極から学ぶ地球の未来」

    公益財団法人 日本極地研究振興会  2020.4

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    Audience:Infants, Schoolchildren, Junior students, High school students

    Type:Other

  • 中学生用ESD(Education for sustainable development)副読本「南極・北極から地球の未来を考える」

    公益財団法人 日本極地研究振興会  2020.4

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    Audience:Infants, Schoolchildren, Junior students, High school students

    Type:Other

  • 北極温暖化で変わる!?異常気象のリスク

    南極&北極の魅力講演会  東京  2020.2

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    Audience:General, Scientific, Company, Civic organization, Governmental agency

    Type:Lecture

  • 北極海氷減少が異常気象のリスクを変えるのか?

    2019年度北極域研究推進プロジェクト公開講演会『北極研究から見えてきたもの』  東京大学本郷キャンパス  2019.12

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    Audience:General, Scientific, Company, Civic organization, Governmental agency

    Type:Lecture

  • クイズ!先端研の研究を学ぼう「先端研公開講座きしょうがく」

    東京大学先端科学技術研究センター  東京大学先端科学技術研究センター  2018.6

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    Audience:General, Scientific, Company, Civic organization, Governmental agency

    Type:Other

  • 異常気象とイベントアトリビューション

    第8回温暖化リスクメディアフォーラム〜温暖化適応研究の新潮流〜  東京  2015.12

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    Audience:General, Scientific, Company, Civic organization, Governmental agency

    Type:Lecture

  • 地球温暖化は異常気象のリスクを変えているのか?~温暖化の寄与を推定する~

    平成27年度気候変動リスク情報創生プログラム公開シンポジウム  一橋大学  2015.10

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    Audience:General, Scientific, Company, Civic organization, Governmental agency

    Type:Lecture

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Media Coverage

  • 中高緯度の海が偏西風の蛇行を強める Internet

    東京大学 海洋アライアンス  https://www.oa.u-tokyo.ac.jp/column/trivia/0058/index.html  2024.4

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    Author:Other 

  • 九大など、“偏西風蛇行の増幅”仕組み解明 大気・海洋の熱が影響” Newspaper, magazine

    日刊工業新聞  2024.3

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    九大など、“偏西風蛇行の増幅”仕組み解明 大気・海洋の熱が影響”

  • 異常気象と地球温暖化の脅威 Newspaper, magazine

    Newton 別冊「天気と気象」  2023.4

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    異常気象と地球温暖化の脅威

  • 寒波と温暖化 10年に一度の最強寒波に温暖化が関係? TV or radio program

    TBSサンデーモーニング(風をよむ)  2023.1

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    寒波と温暖化 10年に一度の最強寒波に温暖化が関係?

  • 地球温暖化と災害 Newspaper, magazine

    Newton 別冊「地球温暖化の教科書」  2022.5

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    地球温暖化と災害

  • 異常気象と地球温暖化の脅威 Newspaper, magazine

    Newton 別冊「ゼロからわかる天気と気象」  2021.4

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    異常気象と地球温暖化の脅威

  • 異常気象と地球温暖化の脅威 Newspaper, magazine

    Newton 別冊「天気と気象の教科書」  2019.4

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    異常気象と地球温暖化の脅威

  • ユーラシア大陸寒冷化 北極海の海氷減原因 Newspaper, magazine

    宮崎日日新聞  2019.1

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    ユーラシア大陸寒冷化 北極海の海氷減原因

  • Melting sea ice makes northern winters more severe https://www.nature.com/articles/d41586-019-00132-x Newspaper, magazine

    Nature  2019.1

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    Melting sea ice makes northern winters more severe
    https://www.nature.com/articles/d41586-019-00132-x

  • 地球温暖化で北極海の海氷が減り、冬の中央ユーラシアが寒くなってきた https://scienceportal.jst.go.jp/news/newsflash_review/newsflash/2019/01/20190123_01.html Internet

    Science Portal  2019.1

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    地球温暖化で北極海の海氷が減り、冬の中央ユーラシアが寒くなってきた
    https://scienceportal.jst.go.jp/news/newsflash_review/newsflash/2019/01/20190123_01.html

  • 豪雨被害、本県も可能性 Newspaper, magazine

    宮崎日日新聞  2018.7

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    豪雨被害、本県も可能性

  • 減る北極氷 日本に寒風 Newspaper, magazine

    日本経済新聞  2017.1

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    減る北極氷 日本に寒風

  • 北極海の海氷減少と日本の寒冬 TV or radio program

    気象情報(NHK総合),首都圏ニュース845(NHK総合)  2016.12

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    北極海の海氷減少と日本の寒冬

  • 異常気象と地球温暖化の脅威 Newspaper, magazine

    Newton 9月号 24-53  2016.9

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    異常気象と地球温暖化の脅威

  • 温暖化で大型台風3倍に Newspaper, magazine

    朝日小学生新聞  2016.2

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    温暖化で大型台風3倍に

  • 教えて!お天気キャスター 地球温暖化でどうなる異常気象 TV or radio program

    NHK総合(取材協力)  2015.12

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    教えて!お天気キャスター 地球温暖化でどうなる異常気象

  • 温暖化でも ドカ雪 Newspaper, magazine

    毎日新聞  2015.12

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    温暖化でも ドカ雪

  • ユーラシア大陸:厳冬は地球温暖化の影響 Newspaper, magazine

    毎日新聞  2014.10

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    ユーラシア大陸:厳冬は地球温暖化の影響

  • Global warming ‘will make our winters colder Newspaper, magazine

    The Independent  2014.10

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    Global warming ‘will make our winters colder

  • Global warming has doubled risk of harsh winters in Eurasia, research finds Newspaper, magazine

    The Guardian  2014.10

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    Global warming has doubled risk of harsh winters in Eurasia, research finds

  • Arctic sea ice loss responsible for Eurasia's deep chill http://news.sciencemag.org/asia/2014/10/arctic-sea-ice-loss-responsible-eurasias-deep-chill Newspaper, magazine

    Science  2014.10

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    Arctic sea ice loss responsible for Eurasia's deep chill
    http://news.sciencemag.org/asia/2014/10/arctic-sea-ice-loss-responsible-eurasias-deep-chill

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