Updated on 2025/01/30

写真a

 
NOZAWA Toru
 
Organization
Faculty of Environmental, Life, Natural Science and Technology Professor
Position
Professor
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Degree

  • Doctor of Science ( 1997.1   Kyoto University )

Research Interests

  • global warming

  • 気候変化

  • climate change

  • 地球温暖化

Research Areas

  • Natural Science / Atmospheric and hydrospheric sciences

  • Environmental Science/Agriculture Science / Environmental dynamic analysis

Education

  • Kyoto University   大学院理学研究科   地球物理学専攻博士課程

    1993.4 - 1996.7

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  • Kyoto University   大学院理学研究科   地球物理学専攻修士課程

    1991.4 - 1993.3

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    Country: Japan

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  • Kyoto University   理学部  

    1987.4 - 1991.3

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    Country: Japan

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Research History

  • Okayama University   学術研究院環境生命自然科学学域   Professor

    2023.4

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  • Okayama University   学術研究院自然科学学域   Professor

    2021.4 - 2023.4

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  • Okayama University   The Graduate School of Natural Science and Technology   Professor

    2013.4 - 2021.3

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  • National Institute for Environmental Studies   地球環境研究センター   Head

    2011.4 - 2013.3

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  • National Institute for Environmental Studies   大気圏環境研究領域   Head

    2006.4 - 2011.3

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Professional Memberships

 

Papers

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

    Masayoshi ISHII, Hirotaka KAMAHORI, Hisayuki KUBOTA, Masumi ZAIKI, Ryo MIZUTA, Hiroaki KAWASE, Masaya NOSAKA, Hiromasa YOSHIMURA, Naga OSHIMA, Eiki SHINDO, Hiroshi KOYAMA, Masato MORI, Shoji HIRAHARA, Yukiko IMADA, Kohei YOSHIDA, Toru NOZAWA, Tetsuya TAKEMI, Takashi MAKI, Akio NISHIMURA

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

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    Publishing type:Research paper (scientific journal)   Publisher:Meteorological Society of Japan  

    DOI: 10.2151/jmsj.2024-010

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  • The Importance of Ocean Dynamical Feedback for Understanding the Impact of Mid-High-Latitude Warming on Tropical Precipitation Change Reviewed

    Masakazu Yoshimori, Ayako Abe-Ouchi, Hiroaki Tatebe, Toru Nozawa, Akira Oka

    JOURNAL OF CLIMATE   31 ( 6 )   2417 - 2434   2018.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER METEOROLOGICAL SOC  

    It has been shown that asymmetric warming between the Northern and Southern Hemisphere extratropics induces a meridional displacement of tropical precipitation. This shift is believed to be due to the extra energy transported from the differentially heated hemisphere through changes in the Hadley circulation. Generally, the column-integrated energy flux in the mean meridional overturning circulation follows the direction of the upper, relatively dry branch, and tropical precipitation tends to be intensified in the hemisphere with greater warming. This framework was originally applied to simulations that did not include ocean dynamical feedback, but was recently extended to take the ocean heat transport change into account. In the current study, an atmosphere-ocean general circulation model applied with a regional nudging technique is used to investigate the impact of extratropical warming on tropical precipitation change under realistic future climate projections. It is shown that warming at latitudes poleward of 40 degrees causes the northward displacement of tropical precipitation from October to January. Warming at latitudes poleward of 60 degrees alone has a much smaller effect. This change in the tropical precipitation is largely explained by the atmospheric moisture transport caused by changes in the atmospheric circulation. The larger change in ocean heat transport near the equator, relative to the atmosphere, is consistent with the extended energy framework. The current study provides a complementary dynamical framework that highlights the importance of midlatitude atmospheric eddies and equatorial ocean upwelling, where the atmospheric eddy feedback modifies the Hadley circulation resulting in the northward migration of precipitation and the ocean dynamical feedback damps the northward migration from the equator.

    DOI: 10.1175/JCLI-D-17-0402.1

    Web of Science

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  • Effect of retreating sea ice on Arctic cloud cover in simulated recent global warming Reviewed

    Manabu Abe, Toru Nozawa, Tomoo Ogura, Kumiko Takata

    ATMOSPHERIC CHEMISTRY AND PHYSICS   16 ( 22 )   14343 - 14356   2016.11

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:COPERNICUS GESELLSCHAFT MBH  

    This study investigates the effect of sea ice reduction on Arctic cloud cover in historical simulations with the coupled atmosphere-ocean general circulation model MIROC5. Arctic sea ice has been substantially retreating since the 1980s, particularly in September, under simulated global warming conditions. The simulated sea ice reduction is consistent with satellite observations. On the other hand, Arctic cloud cover has been increasing in October, with about a 1-month lag behind the sea ice reduction. The delayed response leads to extensive sea ice reductions because the heat and moisture fluxes from the underlying open ocean into the atmosphere are enhanced. Sensitivity experiments with the atmospheric part of MIROC5 clearly show that sea ice reduction causes increases in cloud cover. Arctic cloud cover increases primarily in the lower troposphere, but it decreases in the near-surface layers just above the ocean; predominant temperature rises in these near-surface layers cause drying (i.e., decreases in relative humidity), despite increasing moisture flux. Cloud radiative forcing due to increases in cloud cover in autumn brings an increase in the surface downward longwave radiation (DLR) by approximately 40-60% compared to changes in clear-sky surface DLR in fall. These results suggest that an increase in Arctic cloud cover as a result of reduced sea ice coverage may bring further sea ice retreat and enhance the feedback processes of Arctic warming.

    DOI: 10.5194/acp-16-14343-2016

    Web of Science

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  • Asymmetric impact of the physiological effect of carbon dioxide on hydrological responses to instantaneous negative and positive CO2 forcing Reviewed

    Manabu Abe, Hideo Shiogama, Tokuta Yokohata, Seita Emori, Toru Nozawa

    CLIMATE DYNAMICS   45 ( 7-8 )   2181 - 2192   2015.10

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

    We conducted sensitivity experiments using a coupled atmosphere-ocean general circulation model to examine the asymmetry between the hydrological responses to instantaneous positive and negative CO2 forcing and the impact of the CO2 physiological effects (CDPEs) on these responses. This study focuses on the fast response occurring on time scales shorter than 1 year after imposing CO2 forcing. Experiments investigating the CO2 physiological effect show that the fast response of precipitation to positive CO2 forcing is a decrease in the global and annual mean, whereas that of negative forcing is an increase the global and annual mean precipitation. The fast global precipitation response to negative forcing is stronger than the response to positive forcing. In contrast, the experiments without the CDPE reveal similar magnitudes of the fast global precipitation responses to negative and positive CO2 forcing. Significant differences in the magnitudes of the fast precipitation response due to the CDPE are found in tropical regions such as the Amazon Basin, the Maritime Continents, and tropical Africa, where C3-type plants are common. The stomatal conductance of plant leaves is decreased by both positive and negative CO2 forcing, which suppress the transpiration from the leaves. Consequently, the CDPE enhances the asymmetry of the fast precipitation responses to positive and negative CO2 forcing. The asymmetric impact of CDPE requires a careful evaluation of future hydrological changes which is constrained by paleoclimate evidence.

    DOI: 10.1007/s00382-014-2465-1

    Web of Science

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  • Temperature scaling pattern dependence on representative concentration pathway emission scenarios A Letter (vol 112, pg 535, 2012) Reviewed

    Yasuhiro Ishizaki, Hideo Shiogama, Seita Emori, Tokuta Yokohata, Toru Nozawa, Tomoo Ogura, Manabu Abe, Masakazu Yoshimori, Kiyoshi Takahashi

    CLIMATIC CHANGE   125 ( 2 )   277 - 277   2014.7

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MISC

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Research Projects

  • 積雪が稀な地域での大雪発生状況の把握と現在及び将来の大雪発生ポテンシャルの評価

    Grant number:19H01377  2019.04 - 2023.03

    日本学術振興会  科学研究費助成事業  基盤研究(B)

    川瀬 宏明, 野沢 徹, 大庭 雅道, 西井 和晃

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    Grant amount:\16770000 ( Direct expense: \12900000 、 Indirect expense:\3870000 )

    本課題は雪の少ない本州の太平洋側などを対象に、退蔵されたままの過去の積雪データを救出し、過去50年間の積雪分布図及び大雪の起こりやすさを指標化した大雪発生ポテンシャルマップを作成することを目的とする、また、数値シミュレーションや機械学習を用いて稀な大雪を引き起こす気象場を明らかにする。
    本年度は昨年度に引き続き、関東から九州にかけての区内観測データのデジタル化を進め、予定していたデジタル化はほぼ終了した。デジタル化した区内観測データを用いて、関東地方、東海地方、及び中国地方における過去の極端な大雪の事例を抽出し、その時に降雪分布及び大気場の影響を調べた。関東地方の大雪はこれまでも指摘されている通り、南岸低気圧によってもたらされたが、大雪の発生するパターンは大きく分けて3つ(南部沿岸部、東部、内陸部)あることが分かった。
    気象庁55年長期再解析データを基に1958年から2020年までを5km格子で計算したデータを区内観測データと比較したところ、積雪・降雪の統計値の再現性が良いことが分かった。また、関東の大雪について長期変化を調べると、降雪量は減少傾向であることが分かった。一方で、降水量は逆に増加トレンドを示していたため、区内観測点が多く分布する低標高地域では、気温上昇による降雪から降雨への変化の影響が大きく降雪量が減少したと考えられる。
    1958年以降の南岸低気圧の大雪を、自己組織化マップを用いて分析したところ、南岸低気圧の頻度は後半年の方が増加し、南岸低気圧にともなう降水量も増加していることが分かった。一方で、南岸低気圧パターンの降雪量は関東、東海、瀬戸内のいずれの地域でも減少した。

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  • Recent surface darkening and abrupt melting of Greenland ice sheet (SIGMA2)

    Grant number:16H01772  2016.04 - 2020.03

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

    Aoki Teruo

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    Grant amount:\41080000 ( Direct expense: \31600000 、 Indirect expense:\9480000 )

    In order to clarify the recent surface melting of the Greenland ice sheet, in-situ field observations, satellite remote sensing and numerical modelling were conducted. In the field observations, existing automatic weather station observations were continued and the data were published. Ice core samples were analyzed to characterize water vapor and mineral dust transport. In satellite remote sensing, we developed an algorithm to retrieve the snow and ice physical parameters using a non-spherical snow particle shape model and quantified the causes of ice sheet surface darkening. In numerical modelling, a regional meteorological model including the detailed processes of light-absorbing aerosols (LAA) was developed. A regional meteorological model including snow metamorphism was used to simulate the time and spatial variation of ice sheet surface melting. In addition, the radiative forcing due to LAA in the atmosphere and snow/ice was estimated by an earth system model.

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  • Numerical modeling studies on the long-term climate variability aimed at detecting anthropogenic signals on the climate change

    Grant number:18310016  2006 - 2008

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

    NOZAWA Toru, NAGASHIMA Tatsuya, SHIOGAMA Hideo

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    Grant amount:\18040000 ( Direct expense: \15700000 、 Indirect expense:\2340000 )

    人間活動に伴う気候変化シグナルの検出に資するために、長期内部変動である気候の揺らぎに対して外的な気候変動要因が及ぼす影響について調べた。温室効果ガスの増加など人為的な気候変動要因のみ考慮した場合や、太陽変動など自然的な気候変動要因のみ考慮した場合など、仮想的な数値シミュレーション結果を統計的に比較解析した結果、気候の揺らぎは外的な気候変動要因による著しい変調を受けないと考えられることが示唆された。

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  • 長期気候変動の機構解明

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    Grant type:Competitive

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  • Analysis of long-term climate change

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    Grant type:Competitive

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Class subject in charge

  • Introduction to Earth and Planetary Atmospheric Sciences (2024academic year) Second semester  - 月5~6

  • Introduction to Earth and Planetary Atmospheric Sciences (2024academic year) Second semester  - 火5~6

  • Advanced Seminar on Earth and Planetary Sciences (2024academic year) Year-round  - その他

  • Environmental Earth Sciences (2024academic year) Prophase  - その他

  • Directed Reading in Earth Science 2 (2024academic year) Fourth semester  - 火3~4

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