エアロゾルの気候影響評価
キーワード：エアロゾル, 大気放射, 放射強制, 大気大循環モデル, 雲・エアロゾル相互作用, 気候変動予測
1997.04.

短寿命気候強制因子による気候変動・環境影響に対応する緩和策推進のための研究
2021.04～2026.03, 代表者：竹村俊彦, 九州大学, 独立行政法人環境再生保全機構
大気中のPM2.5などの微粒子（エアロゾル）や、光化学オキシダントであるオゾンなどの微量気体は、大気汚染物質であると同時に気候変動を引き起こす物質であり、短寿命気候強制因子 (short-lived climate forcers (SLCFs)) と呼ばれている。このプロジェクトでは、排出源および大気中の時空間分布が偏在しているSLCFsの地域ごと及び組成ごとの気候変動・環境影響を定量的に評価し、同時に影響緩和へ向けた排出量削減シナリオを策定するための研究を推進する。.

短寿命気候強制因子による気候変動・環境影響に対応する適応・緩和策推進のための調査研究
2020.04～2021.03, 代表者：竹村俊彦, 九州大学, 独立行政法人環境再生保全機構
排出源および大気中の時空間分布が偏在している短寿命気候強制因子 (SLCFs) の地域規模での気候変動および環境影響を定量的に評価し、同時に影響緩和へ向けたシナリオを策定するための研究を戦略的研究開発（Ⅰ）にて実施することを目指して、必要な検討・現状分析および事前準備を行う。.

階層的数値モデル群による短寿命気候強制因子の組成別・地域別定量的気候影響評価
2019.04～2024.03, 代表者：竹村俊彦, 九州大学, 独立行政法人日本学術振興会
大気中のPM2.5などの微粒子（エアロゾル）や、光化学オキシダントであるオゾンなどの微量気体は、大気汚染物質であると同時に気候変動を引き起こす物質であり、短寿命気候強制因子と呼ばれている。それらの気温や降水量などへの影響について、自ら開発を進めてきた気候モデルを用いて、組成ごと・地域ごとに定量的に評価する研究を推進する。気候モデルにおいて不確実性の高いエアロゾルに依存する雲・降水過程の精緻化を図りつつ、また、近年顕在化している極端な気温や降水などの災害に対する短寿命気候強制因子の影響の定量的理解も目指す。.

気候モデルに適用する新しい雲・降水成長スキームの開発
2015.04～2017.03, 代表者：竹村俊彦, 九州大学応用力学研究所, 九州大学
本研究課題では、気候モデルにおける雲粒・氷晶から降水・降雪への成長タイムスケールを適切に表現できる、新しい雲・降水スキームの開発を行う。新しい手法を用いた人工衛星データの解析を綿密に行い、それを参照しながら様々なスキームを試行して、最適パラメタリゼーションを決定する。雲・降水プロセスは気候モデルにおける最大の不確実要素であるため、本研究課題の研究成果は、次世代の気候変動予測シミュレーションに活用され、政策的および社会的に求められている、より精度の高い地球温暖化予測・地球環境予測に大きく寄与することが期待できる。.

エアロゾル地上リモートセンシング観測網による数値モデルの気候変動予測の高度化
2015.04～2020.03, 代表者：竹村俊彦, 九州大学応用力学研究所, 九州大学
本研究課題の研究グループが20年近くにわたり自ら展開してきた地上リモートセンシング観測網SKYNETおよびAD-Netから得られるデータを活用し、数値モデルによるエアロゾルの気候に対する影響の定量的評価を高精度化する。具体的には、１）データ処理手法を統一化し、長期多地点での観測データの標準化を図る。２）両観測網データを複合利用することで解析アルゴリズムを高度化し、長期多地点でのエアロゾルの量および特性の経年変動を高精度で見積もる。３）高度化した観測データを検証材料および同化データとして使用することにより、気候モデルによるエアロゾルの気候影響評価を高精度化する。４）国際的なエアロゾルモデル相互比較プロジェクト等を通じて、IPCC第6次評価報告書へ寄与する。.

数値モデルによる気候・環境変動評価と影響評価
2014.06～2019.03, 代表者：竹村俊彦, 九州大学応用力学研究所, 九州大学
エアロゾル・化学気候モデルを用いて、short-lived climate pollutants (SLCP)の排出量インベントリ・シナリオを用いて、SLCPの濃度変化に伴う現在および将来の気候変動・健康影響・農作物収量変化の評価を行う。その計算結果を解析することにより、温室効果とSLCPの両者を考慮した気候変動緩和のための最適削減経路を提示するための科学的根拠資料を創生する。.

数値モデルによる大気エアロゾルの環境負荷に関する評価および予測の高精度化
2011.02～2014.03, 代表者：竹村俊彦, 九州大学応用力学研究所, 九州大学
特にエアロゾルと雲の関係を表現するモデルを精緻化し、気候変動評価の高精度化を図る。また、データ同化手法を用いたエアロゾル分布週間予測システムを開発する。.

数値モデルを用いた大気エアロゾルの気候に対する影響の予測
2009.04～2011.03, 代表者：竹村俊彦, 九州大学応用力学研究所, 九州大学
エアロゾルの分布および気候に対する影響を、現在から数十年～百年スケールで予測する。.

４次元データ同化手法を用いた全球エアロゾルモデルによる気候影響評価
2009.04～2011.03, 代表者：竹村俊彦, 九州大学応用力学研究所, 九州大学
数値モデルと観測データとを融合して時間変化する大気の状態を高精度で推定する「データ同化」という手法を用いて、エアロゾルの気候に対する影響を評価する際の大きな不確定要素の1つであるエアロゾル排出量の時空間分布に関して、高精度な推定を行う。また、その結果として得られる、従来の研究よりも信頼度の高いことが期待されるエアロゾルの気候に対する影響の評価を行う。.

大気エアロゾル予報モデルの開発
2006.04～2009.03, 代表者：竹村俊彦, 九州大学応用力学研究所, 九州大学
全球エアロゾル輸送・放射モデルSPRINTARSをベースとして全球エアロゾル分布予報モデルを構築し、数日先までの予報を１日１回程度計算してweb等で公開する。.

気象モデルによるエアロゾルの気候影響研究
2002.04～2007.03, 代表者：竹村俊彦, 九州大学応用力学研究所, 九州大学
全球エアロゾル輸送・放射モデルSPRINTARSを用いて、エアロゾルによる気候変動影響の定量的評価を統合的に行う。.

全球エアロゾル輸送・放射モデルを用いたエアロゾルの気象場に対する影響に関する研究
2003.04～2004.10, 代表者：竹村俊彦, 九州大学応用力学研究所, 九州大学
全球エアロゾル輸送・放射モデルSPRINTARSを用いて、エアロゾル直接・間接効果による気象場の変化を解析する。.

Composition Air Quality Climate Interactions Initiative (CACTI)
2021.10, 代表者：Stephanie Fiedler, GEOMAR Helmholtz Centre for Ocean Research Kiel, GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany)
The overall goal of CACTI is to quantify and advance the scientific understanding of the global and regional forcing, climate and air quality responses, and Earth System feedbacks due to atmospheric composition and Short-Lived Climate Forcer (SLCF) emission changes..

Aerosol Model Intercomparison Project (AeroCom)
2003.06, 代表者：Michael Schulz, Stefan Kinne, Laboratoire des Sciences du Climat et de l'Environnement, Max Plank Institute for Meteorology, Laboratoire des Sciences du Climat et de l'Environnement (France)
The AeroCom project is an open international initiative of scientists interested in the advancement of the understanding of the global aerosol and its impact on climate. A large number of observations (including MODIS, POLDER, MISR, AVHHR, SEAWIFS, TOMS, AERONET and surface concentrations) and results from more than 14 global models have been assembled to document and compare state of the art modeling of the global aerosol..

エアロゾルモニタリングシステム開発に関する研究
2014.06～2017.03, 代表者：竹村俊彦, 沖理子, 眞木貴史, 大原利眞, 九州大学, 宇宙航空研究開発機構, 気象研究所, 国立環境研究所, 九州大学, 宇宙航空研究開発機構, 気象研究所, 国立環境研究所
MRI及び九大は、EarthCARE、GCOM-C、GOSAT、次世代ひまわりデータの同化手法の研究を行い、自己が開発したエアロゾル予測システムを改良・運用する。NIESは、エアロゾル排出起源データベースを作成し、衛星や地上観測データによるエアロゾル予測モデルの検証を通じNIESが開発したエアロゾル予測システムを改良・運用する。JAXAは、MRI、九大及びNIESが改良したエアロゾル予測システムの予測結果をユーザへ配布する提供システムの初期検討を行う。.

地球規模の気候・環境変動予測に関する研究（HPCI戦略プログラム分野3）
2011.04～2016.03, 代表者：木本昌秀, 東京大学大気海洋研究所気候システム研究系, 東京大学
毎日の天気や長期予報、あるいは今世紀末の地球温暖化の影響など、全地球規模の気候計算は、さまざまな時間スケールを扱います。計算期間が長くなると計算量も膨大になるため、現在では、明日の天気を計算するときも全球大気モデルでは、雷雲のような一つ一つの雲は扱わず、多数の雲の集団効果を半経験的に推定して計算する方法が採られています。個々の雲を扱うような計算をしていては明日の天気予報に間に合わないからです。この研究では、近い将来このような計算上の制限が緩和されたとき、どのような成果がもたらされるかを、先んじて研究しようとしています。膨大な数の積乱雲からなる台風は、地球温暖化の景況を受けてどのように変容するでしょうか？現在は予報できない、赤道を1ヵ月以上かけて一周するような巨大なクモのかたまりが予測できれば熱帯の天気予報に革命が起こるのではないでしょうか？あるいは、空間的な細かさだけでなく、気候システム中でのさまざまな物質の循環や、化学生物学的な過程を取り入れて、気温や降水量だけでなく、将来の二酸化炭素量や大気汚染の予測は可能にならないでしょうか？従来予測の延長にとどまらず、京コンピュータの画期的な能力を借りて、気候シミュレーションの新しい可能性を探ります。.

大気環境物質のためのシームレス同化システム構築とその応用（気候変動適応研究推進プログラム）
2014.04～2015.03, 代表者：中島映至, 東京大学大気海洋研究所, 東京大学
次世代の全球大気モデルである正20面体格子非静力学モデル（NICAM）と領域モデルを利用して、二酸化炭素と大気汚染物質の両方を同化し、発生源を推定（逆問題）するシステムを構築する。このシステムを関東平野領域に適用して、温暖化・全球大気汚染・都市化の複合影響によって変化するメガシティー環境に社会が適応するための施策案を、国や自治体と協力して作成する。.

直面する地球環境変動の予測と診断（気候変動リスク情報創生プログラム）
2012.04～2017.03, 代表者：木本昌秀, 東京大学大気海洋研究所気候システム研究系, 東京大学
様々な季節から十年までの時間スケールにおいて、観測データを用いて検証可能な気候変動予測システムを構築し、信頼性の高い気候変動予測情報を提供することを目指す。.

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（21世紀気候変動予測革新プログラム）
2007.04～2012.03, 代表者：木本昌秀, 東京大学気候システム研究センター, 東京大学
大気海洋結合気候モデルを高精度・高解像度化して、人為要因による2030年程度までの近未来の気候変化の予測実験を行う。これまでにない高解像度の実験により、温暖化の社会影響評価・政策決定に資する定量情報の提供を図り、地球温暖化問題に対する国際的な取り組みの進展に貢献することを目指す。.

地球システム統合モデルによる長期気候変動予測実験（21世紀気候変動予測革新プログラム）
2007.04～2012.03, 代表者：時岡達志, 海洋研究開発機構, 海洋研究開発機構
地球システム統合モデルを使用して、西暦2300年までの地球温暖化予測実験を行い、CO2安定化シナリオの下での、長期的な地球環境の変化を予測する。また、大気中のCO2濃度を安定化させる上で許容される人為起源CO2排出量を評価する。地球環境変化予測の結果を用いて、予測の不確定性の評価・低減のための実験や、自然災害分野への影響評価を行う。.

高分解能大気海洋モデルを用いた地球温暖化予測に関する研究（人・自然・地球共生プロジェクト）
2002.04～2007.03, 代表者：住明正, 東京大学気候システム研究センター, 東京大学
東京大学気候システム研究センター・国立環境研究所・地球環境フロンティア研究センターの研究者の総力を結集して、高分解能大気海洋結合モデルMIROC（大気：水平解像度約120km (T106), 鉛直50層; 海洋：水平1/4度(経度)ｘ1/6度(緯度), 鉛直45層)を開発し、地球温暖化予測を行い、現在の知見で最も確からしい温暖化に関する予測情報を提供し、温暖化対策や適応策などの政策決定に寄与するとともに、他国のモデルと比較検討することを通して地球温暖化予測の国際標準を作ることによって国際的な枠組み作りの基盤となることを目標とする。.

地球環境変化予測のための地球システム統合モデルの開発（人・自然・地球共生プロジェクト）
2002.04～2007.03, 代表者：松野太郎, 地球環境フロンティア研究センター, 地球環境フロンティア研究センター
地球環境全体の変化、すなわち気候・大気・海洋の組成、陸・海の生態系が相互に影響を与えつつ一体となって変化して行くのをシミュレートできる地球環境（地球システム）の統合モデルを開発する事およびそれを用いて炭素循環のフィードバックを含んだ地球温暖化予測を行う事。.

アジア域の広域大気汚染による大気粒子環境の変調（戦略的創造研究推進事業）
1999.09～2004.06, 代表者：中島映至, 東京大学気候システム研究センター, 東京大学
アジア域の広域大気汚染によるエアロゾルの増加に伴って、同地域の放射エネルギー収支と雲・降水場がどのように変調するのかを明らかにする。そのために、（1）エアロゾル、雲粒、霧粒までの雲のライフサイクルに関わる全粒径分布の形成機構と（2）粒子系の光学特性パラメーターと大気力学的、化学的パラメーターとの間の依存性に関する研究を行う。本研究を通して、温暖化予測や広域汚染の気候影響における国際的議論での強い足場になるような知見を得ることとする。.

主要著書

主要原著論文

1.	Yuki Kusakabe, Toshihiko Takemura, Formation of the North Atlantic Warming Hole by reducing anthropogenic sulphate aerosols, Scientific Reports, 10.1038/s41598-022-27315-3, 13, 1, 2023.01.
2.	Toshihiko Takemura, Return to different climate states by reducing sulphate aerosols under future CO2 concentrations, Scientific Reports, 10.1038/s41598-020-78805-1, 10, 1, 2020.12, [URL], It is generally believed that anthropogenic aerosols cool the atmosphere; therefore, they offset the global warming resulting from greenhouse gases to some extent. Reduction in sulphate, a primary anthropogenic aerosol, is necessary for mitigating air pollution, which causes atmospheric warming. Here, the changes in the surface air temperature under various anthropogenic emission amounts of sulphur dioxide (SO2), which is a precursor of sulphate aerosol, are simulated under both present and doubled carbon dioxide (CO2) concentrations with a climate model. No previous studies have conducted explicit experiments to estimate the temperature changes due to individual short-lived climate forcers (SLCFs) in different climate states with atmosphere–ocean coupled models. The simulation results clearly show that reducing SO2 emissions at high CO2 concentrations will significantly enhance atmospheric warming in comparison with that under the present CO2 concentration. In the high latitudes of the Northern Hemisphere, the temperature change that will occur when fuel SO2 emissions reach zero under a doubled CO2 concentration will be approximately 1.0 °C, while this value will be approximately 0.5 °C under the present state. This considerable difference can affect the discussion of the 1.5 °C/2 °C target in the Paris Agreement..
3.	Toshihiko Takemura, Kentaroh Suzuki, Weak global warming mitigation by reducing black carbon emissions, Scientific Reports, 10.1038/s41598-019-41181-6, 9, 1, 4419, 2019.12, [URL], © 2019, The Author(s). Reducing black carbon (BC), i.e. soot, in the atmosphere is a potential mitigation measure for climate change before revealing the effect of reducing anthropogenic carbon dioxide (CO 2 ) because BC with shorter lifetime than CO 2 absorbs solar and infrared radiation. BC has a strong positive radiative forcing in the atmosphere, as indicated in many previous studies. Here, we show that the decline in surface air temperatures with reduced BC emissions is weaker than would be expected from the magnitude of its instantaneous radiative forcing at the top of the atmosphere (TOA). Climate simulations show that the global mean change in surface air temperature per unit of instantaneous radiative forcing of BC at the TOA is about one-eighth that of sulphate aerosols, which cool the climate through scattering solar radiation, without absorption. This is attributed to the positive radiation budget of BC being largely compensated for by rapid atmospheric adjustment, whereas the radiative imbalance due to sulphate aerosols drives a slow response of climate over a long timescale. Regional climate responses to short-lived species are shown to exhibit even more complex characteristics due to their heterogeneous spatial distributions, requiring further analysis in future studies..
4.	Toshihiko Takemura, Distributions and climate effects of atmospheric aerosols from the preindustrial era to 2100 along Representative Concentration Pathways (RCPs) simulated using the global aerosol model SPRINTARS, Atmospheric Chemistry and Physics, 10.5194/acp-12-11555-2012, 12, 23, 11555-11572, 2012.12, [URL], Global distributions and associated climate effects of atmospheric aerosols were simulated using a global aerosol climate model, SPRINTARS, from 1850 to the present day and projected forward to 2100. Aerosol emission inventories used by the Coupled Model Intercomparison Project Phase 5 (CMIP5) were applied to this study. Scenarios based on the Representative Concentration Pathways (RCPs) were used for the future projection. Aerosol loading in the atmosphere has already peaked and is now reducing in Europe and North America. However, in Asia where rapid economic growth is ongoing, aerosol loading is estimated to reach a maximum in the first half of this century. Atmospheric aerosols originating from the burning of biomass have maintained high loadings throughout the 21st century in Africa, according to the RCPs. Evolution of the adjusted forcing by direct and indirect aerosol effects over time generally correspond to the aerosol loading. The probable future pathways of global mean forcing differ based on the aerosol direct effect for different RCPs. Because aerosol forcing will be close to the preindustrial level by the end of the 21st century for all RCPs despite the continuous increases in greenhouse gases, global warming will be accelerated with reduced aerosol negative forcing..
5.	Toshihiko Takemura, Hisashi Nakamura, Teruyuki Nakajima, Tracing airborne particles after Japan's nuclear plant explosion, Eos, 10.1029/2011EO450002, 92, 45, 397-398, 2011.11, [URL], The powerful Tohoku earthquake and consequent tsunami that occurred off the east coast of Japan on 11 March 2011 devastated dozens of coastal cities and towns, causing the loss of more than 15,000 lives and leaving close to 4000 people still missing. Although nuclear reactors at the Fukushima Daiichi Nuclear Power Plant, located on the Pacific coast, stopped their operation automatically upon the occurrence of the Mw 9.0 quake [Showstack, 2011], the cooling system for nuclear fuel broke down. From 12 to 16 March, vapor and hydrogen blasts destroyed the buildings that had contained the reactors, resulting in the release into the atmosphere of radioactive materials such as sulfur-35, iodine-131, cesium-134, and cesium-137, which collectively can cause harmful health effects such as tissue damage and increased risk of cancer (particularly in children), depending on dose. Most of those materials emitted from the power plant rained out onto the grounds within its vicinity and forced tens of thousands within a 20-kilometer radius to evacuate (residents to the northwest of the site within about 40 kilometers also were moved from their homes). Some of the radioactive materials were transported and then detected at such distant locations as North America and Europe, although the level of radiation dose was sufficiently low not to affect human health in any significant manner..
6.	Toshihiko Takemura, Tomoe Uchida, Global Climate Modeling of Regional Changes in Cloud, Precipitation, and Radiation Budget Due to the Aerosol Semi-Direct Effect of Black Carbon, SOLA, 10.2151/sola.2011-046, 7, 181-184, 2011.11, [URL], The aerosol semi-direct effect is generally explained as follows: aerosols, such as black carbon (BC) and mineral dust, absorb solar radiation, which warms and stabilizes the atmosphere, resulting in reduced cloudiness and cloud formation. However, the present study suggests that BC can intensify atmospheric instability and thus increase cloud water and precipitation if the BC is concentrated near the surface. Simulations using a global aerosol climate model, based on a general circulation model, show decreased cloud water over biomass-burning regions where BC is emitted to the free troposphere through the boundary layer. In contrast, increased cloud water is indicated over East and South Asia where BC from urban and industrial activities is concentrated near the surface. While the global mean change in the radiation budget at the top of the atmosphere due to the semi-direct effect of BC is estimated to be as small as +0.06 W m(-2), regional changes in cloud water, precipitation, and shortwave radiation are suggested to be large enough to modify meteorological conditions in urban and biomass-burning regions..
7.	Toshihiko Takemura, Hisashi Nakamura, Masayuki Takigawa, Hiroaki Kondo, Takehiko Satomura, Takafumi Miyasaka, Teruyuki Nakajima, A Numerical Simulation of Global Transport of Atmospheric Particles Emitted from the Fukushima Daiichi Nuclear Power Plant, SOLA, 10.2151/sola.2011-026, 7, 101-104, 2011.07, [URL], The powerful tsunami generated by the massive earthquake that occurred east of Japan on March 11, 2011 caused serious damages of the Fukushima Daiichi Nuclear Power Plant on its cooling facilities for nuclear reactors. Hydrogen and vapor blasts that occurred until March 15 outside of the reactors led to the emission of radioactive materials into the air. Here we show a numerical simulation for the long-range transport from the plant to the U. S. and even Europe with a global aerosol transport model SPRINTARS. Large-scale updraft organized by a low-pressure system traveling across Japan from March 14 to 15 was found effective in lifting the particles from the surface layer to the level of a westerly jet stream that could carry the particles across the Pacific within 3 to 4 days. Their simulated concentration rapidly decreases to the order of 10(-8) of its initial level, consistent with the level detected in California on March 18. The simulation also reproduces the subsequent trans-Atlantic transport of those particles by a poleward-deflected jet stream, first toward Iceland and then southward to continental Europe as actually observed..
8.	Toshihiko Takemura, Mio Egashira, Kanako Matsuzawa, H. Ichijo, Ryota O'ishi, Ayako Abe-Ouchi, A simulation of the global distribution and radiative forcing of soil dust aerosols at the Last Glacial Maximum, Atmospheric Chemistry and Physics, 10.5194/acp-9-3061-2009, 9, 9, 3061-3073, 2009.05, [URL], In this study an integrated simulation of the global distribution and the radiative forcing of soil dust aerosols at the Last Glacial Maximum (LGM) is performed with an aerosol climate model, SPRINTARS. It is compared with another simulation for the present climate condition. The global total emission flux of soil dust aerosols at the LGM is simulated to be about 2.4 times as large as that in the present climate, and the simulated deposition flux is in general agreement with estimations from ice core and marine sediment samplings though it appears to be underestimated over the Antarctic. The calculated direct radiative forcings of soil dust aerosols at the LGM is close to zero at the tropopause and -0.4 W m(-2) at the surface. These radiative forcings are about twice as large as those in the present climate. SPRINTARS also includes the microphysical parameterizations of the cloud-aerosol interaction both for liquid water and ice crystals, which affect the radiation budget. The positive radiative forcing from the indirect effect of soil dust aerosols is mainly caused by their properties to act as ice nuclei. This effect is simulated to be smaller (-0.9 W m(-2)) at the LGM than in the present. It is suggested that atmospheric dust might contribute to the cold climate during the glacial periods both through the direct and indirect effects, relative to the interglacial periods..
9.	Toshihiko Takemura, Yoram J. Kaufman, Lorraine A. Remer, Teruyuki Nakajima, Two competing pathways of aerosol effects on cloud and precipitation formation, Geophysical Research Letters, 10.1029/2006GL028349, 34, 4, L04802-L04802, L04802, 2007.02, [URL], Aerosols may influence cloud formation through two pathways: One is the effect on cloud microphysics by forming smaller and more numerous cloud droplets reducing precipitation and consequently enhancing cloud lifetime. The second is referred to as the aerosol dynamic-hydrological effect in which the aerosol direct, semi-direct, and indirect effects can modulate atmospheric radiation, which perturbs atmospheric circulation, leading to redistributions of clouds and precipitation. Here this study examines climate sensitivities using a general circulation model coupled with an aerosol transport-radiation model. The model is run first with prescribed meteorology in order to isolate the cloud microphysical effect. It is run in a separate experiment with internally generated meteorology that includes dynamic-hydrological effect as the aerosols modify clouds and interact with the radiation. We find in some regions that the dynamic-hydrological effect in the free model runs counteracts the microphysical effects seen in the prescribed runs..
10.	Toshihiko Takemura, Yoko Tsushima, Tokuta Yokohata, Toru Nozawa, Tatsuya Nagashima, Teruyuki Nakajima, Time evolutions of various radiative forcings for the past 150 years estimated by a general circulation model, Geophysical Research Letters, 10.1029/2006GL026666, 33, 19, L19705-L19705-5, L19705, 2006.10, [URL], Time series of the instantaneous radiative forcings for main anthropogenic and natural forcing agents from the year 1850 to 2000 are evaluated at the Earth's surface as well as at the tropopause with an atmospheric general circulation model. This evaluation corresponds to a simulation of 20th century climate with a synthetic coupled atmosphere-ocean general circulation model. The evaluation indicates that the positive radiative forcing at the tropopause rapidly increases from 1910 to 1950 and after 1970 principally due to long-lived greenhouse gases, while the negative radiative forcing at the surface sharply increases between 1955 and 1965 mainly due to the aerosol direct and indirect effects. This study suggests that a simultaneous analysis of changing rates of the radiative forcing both at the tropopause and surface can explain tendencies of changes in the surface air temperature..
11.	Toshihiko Takemura, Toru Nozawa, Seita Emori, Takashi Y. Nakajima, Teruyuki Nakajima, Simulation of climate response to aerosol direct and indirect effects with aerosol transport-radiation model, Journal of Geophysical Research Atmospheres, 10.1029/2004JD005029, 110, D2, D02202, 2005.01, [URL], [ 1] With a global aerosol transport-radiation model coupled to a general circulation model, changes in the meteorological parameters of clouds, precipitation, and temperature caused by the direct and indirect effects of aerosols are simulated, and its radiative forcing are calculated. A microphysical parameterization diagnosing the cloud droplet number concentration based on the Kohler theory is introduced into the model, which depends not only on the aerosol particle number concentration but also on the updraft velocity, size distributions, and chemical properties of each aerosol species and saturation condition of the water vapor. The simulated cloud droplet effective radius, cloud radiative forcing, and precipitation rate, which relate to the aerosol indirect effect, are in reasonable agreement with satellite observations. The model results indicate that a decrease in the cloud droplet effective radius by anthropogenic aerosols occurs globally, while changes in the cloud water and precipitation are strongly affected by a variation of the dynamical hydrological cycle with a temperature change by the aerosol direct and first indirect effects rather than the second indirect effect itself. However, the cloud water can increase and the precipitation can simultaneously decrease in regions where a large amount of anthropogenic aerosols and cloud water exist, which is a strong signal of the second indirect effect. The global mean radiative forcings of the direct and indirect effects at the tropopause by anthropogenic aerosols are calculated to be -0.1 and -0.9 W m(-2), respectively. It is suggested that aerosol particles approximately reduce 40% of the increase in the surface air temperature by anthropogenic greenhouse gases on the global mean..
12.	Toshihiko Takemura, Teruyuki Nakajima, Akiko Higurashi, Sachio Ohta, Nobuo Sugimoto, Aerosol distributions and radiative forcing over the Asian Pacific region simulated by Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS), Journal of Geophysical Research Atmospheres, 10.1029/2002JD003210, 108, D23, 8659, 8659, 2003.08, [URL], A three-dimensional aerosol transport-radiation model coupled with a general circulation model, Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS), simulates atmospheric aerosol distributions and optical properties. The simulated results are compared with aerosol sampling and optical observations from ground, aircraft, and satellite acquired by intensive observation campaigns over east Asia in spring 2001. Temporal variations of the aerosol concentrations, optical thickness, and Angstrom exponent are in good agreement between the simulation and observations. The midrange values of the Angstrom exponent, even at the Asian dust storm events over the outflow regions, suggest that the contribution of the anthropogenic aerosol, such as carbonaceous and sulfate, to the total optical thickness is of an order comparable to that of the Asian dust. The radiative forcing by the aerosol direct and indirect effects is also calculated. The negative direct radiative forcing is simulated to be over -10 W m(-2) at the tropopause in the air mass during the large-scale dust storm, to which both anthropogenic aerosols and Asian dust contribute almost equivalently. The direct radiative forcing, however, largely depends on the cloud water content and the vertical profiles of aerosol and cloud. The simulation shows that not only sulfate and sea salt aerosols but also black carbon and soil dust aerosols, which absorb solar and thermal radiation, make strong negative radiative forcing by the direct effect at the surface, which may exceed the positive forcing by anthropogenic greenhouse gases over the east Asian region..
13.	T Takemura, Uno, I, T Nakajima, A Higurashi, Sano, I, Modeling study of long-range transport of Asian dust and anthropogenic aerosols from East Asia, Geophysical Research Letters, 10.1029/2002GL016251, 29, 24, 2158, 2002.12, [URL], [1] A three-dimensional aerosol transport-radiation model, SPRINTARS, successfully simulates the long-range transport of the large-scale Asian dust storms from East Asia to North America which crossed the North Pacific Ocean during the springtime of 2001 and 2002. It is found from the calculated dust optical thickness that 10 to 20% of the Asian dust around Japan reached North America. The simulation also reveals the importance of the contribution of anthropogenic aerosols, which are carbonaceous and sulfate aerosols emitted from the industrialized areas in East Asia, to air turbidity during the dust storms. The contribution of the anthropogenic aerosol to the total optical thickness is simulated to be of a comparable order to that of the Asian dust, which is consistent with the observed values of the particle size index from the satellite and ground-based sun/sky photometry..
14.	Toshihiko Takemura, Teruyuki Nakajima, Oleg Dubovik, Brent N. Holben, Stefan Kinne, Single-scattering albedo and radiative forcing of various aerosol species with a global three-dimensional model, Journal of Climate, 10.1175/1520-0442(2002)0152.0.CO;2, 15, 4, 333-352, 2002.02, [URL], Global distributions of the aerosol optical thickness, Angstromngstrom exponent, and single-scattering albedo are simulated using an aerosol transport model coupled with an atmospheric general circulation model. All the main tropospheric aerosols are treated, that is, carbonaceous (organic and black carbons), sulfate, soil dust, and sea salt aerosols. The simulated total aerosol optical thickness, Angstromngstrom exponent, and single-scattering albedo for mixtures of four aerosol species are compared with observed values from both optical ground-based measurements and satellite remote sensing retrievals at dozens of locations including seasonal variations. The mean difference between the simulation and observations is found to be less than 30% for the optical thickness and less than 0.05 for the single-scattering albedo in most regions. The simulated single-scattering albedo over the Saharan region is, however, substantially smaller than the observation, though the standard optical constant of soil dust is used in this study. The radiative forcing by the direct effect of the main tropospheric aerosols is then estimated. The global annual mean values of the total direct radiative forcing of anthropogenic carbonaceous plus sulfate aerosols are calculated to be -0.19 and -0.75 W m(-2) under whole-sky and clear-sky conditions at the tropopause, respectively..
15.	Toshihiko Takemura, Teruyuki Nakajima, Toru Nozawa, Kazuma Aoki, Simulation of future aerosol distribution, radiative forcing, and long-range transport in East Asia, Journal of the Meteorological Society of Japan, 10.2151/jmsj.79.1139, 79, 6, 1139-1155, 2001.12, [URL], Distributions of aerosol concentrations, optical properties, and wet deposition fluxes are simulated for the next fifty years using an aerosol transport model coupled with an atmospheric general circulation model. Treated species are sulfur dioxide, and all the main tropospheric aerosols, i.e., carbonaceous (black and organic carbons), sulfate, soil dust, and sea salt. We especially pay attention to distributions of anthropogenic carbonaceous aerosols, sulfate aerosols, and sulfur dioxide. The simulation uses the Special Report on Emissions Scenarios (SRES) of the Intergovernmental Panel on Climate Change (IPCC) as the future emission scenarios of anthropogenic pollutants. Simulated results suggest that carbonaceous aerosols continue to increase over industrial and densely populated regions for the next five decades, whereas sulfate aerosols decrease around Europe and North America. The aerosol single scattering albedo in the future is, therefore, calculated to become small gradually in the mid- and high-latitudes of the Northern Hemisphere. Sulfate aerosols and sulfur wet deposition fluxes are, on the other hand, simulated to increase only over East Asia. Black carbon and sulfate aerosols around Japan in 2050 are simulated to be two or three times as large as those in 2000 with one of the SIZES scenarios. Hence this suggests that pollutants originating from the East Asian continent can seriously affect the atmospheric quality in Japan in the next several decades..
16.	Toshihiko Takemura, Hajime Okamoto, Yoshihiro Maruyama, Atusi Numaguti, Akiko Higurashi, Teruyuki Nakajima, Global three-dimensional simulation of aerosol optical thickness distribution of various origins, Journal of Geophysical Research Atmospheres, 10.1029/2000JD900265, 105, 14, 17853-17873, 2000.07, [URL], A global three-dimensional model that can treat transportation of various species of aerosols in the atmosphere is developed using a framework of an atmospheric general circulation model (AGCM). Main aerosols in the troposphere, i.e., soil dust, carbonaceous (organic and black carbon), sulfate, and sea-salt aerosols, are introduced into this model. Prior to the model calculations the meteorological parameters are calculated by the AGCM with the nudging technique using reanalysis data. To evaluate aerosol effects on the climate system and to compare simulated results with observations, the optical thickness and Angstrom exponent are also calculated taking into account the size distribution and composition. The model results are validated by both measured surface aerosol concentrations and retrieved aerosol optical parameters from National Oceanic and Atmospheric Administration/Advanced Very High Resolution Radiometer. A general agreement is found between the simulated result and the observation globally and seasonally. One of the significant results is that the simulated relative contribution of anthropogenic carbonaceous aerosols to the total optical thickness is comparable to that of sulfate aerosols at midlatitudes of the Northern Hemisphere, which agrees with recent observations. This result leads to a conclusion that the radiative effect evaluation of aerosols on the climate system is necessary to be modified because optical properties of carbonaceous aerosols are different from those of sulfate aerosols. The other finding is that the seasonal shift off the west coast of North Africa observed by satellites, i.e., the latitude of the maximum optical thickness moves seasonally, is also reproduced in consideration of a mixed state of soil dust and carbonaceous aerosols. Copyright 2000 by the American Geophysical Union..

主要総説, 論評, 解説, 書評, 報告書等

主要学会発表等

1.

竹村俊彦, 大気エアロゾル（微粒子）予測, 2007.04 地球規模での大気中の微粒子（エアロゾル）の分布を計算する数値モデル SPRINTARS を用いて、1週間先までの大気中のエアロゾル分布を予測するシステムである。1日1回運用され、ホームページ上（http://sprintars.net/forecastj.html）では、全球およびアジア域のエアロゾル分布予測の動画を閲覧できる他、日本各地のエアロゾル濃度は4段階に分類することにより、一般にも理解しやすい表現を採っている。アジア大陸での急速な経済発展に伴う日本への越境大気汚染の増大が懸念されており、本システムが日々の社会活動にとって有益な情報を作成することが期待される。, [URL].

2.

竹村俊彦, 中島映至, 岡本創, 丸山祥宏, 沼口敦, 五藤大輔, SPRINTARS, 2001.10 気候システムに対するエアロゾルの影響及び大気汚染の状況をシミュレートするのを目的として、SPRINTARS (Spectral Radiation-Transport Model for Aerosol Species) は開発されました。 SPRINTARS は東京大学気候システム研究センター・国立環境研究所・地球環境フロンティア研究センターが共有している大気大循環モデル (CCSR/NIES/FRCGC AGCM) をベースとした全球３次元エアロゾル輸送・放射モデルです。取り扱われているエアロゾル種及び前駆体は、対流圏の主要エアロゾル及びその関連気体です。モデル内では、エアロゾルの発生、移流、拡散、除去（雨滴との衝突による除去、雲水への取り込みのよる除去、乾性沈着、重力落下）といった輸送過程を計算しています。特定期間のシミュレーションをするために、風・気温・比湿といった気象場は再解析データを使用してナッジングすることも可能です。放射過程は、各エアロゾルで異なる各波長の複素屈折率、粒径分布、吸湿成長を考慮して計算しています。また、エアロゾルによる雲粒径の変化（第1種間接効果）や降水量の変化（第2種間接効果）も考慮されています。海洋モデル若しくは簡易海洋モデルと結合することにより、フィードバックを含めたエアロゾルによる気候変動をシミュレートすることも可能です。 http://www.sprintars.net/.

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