気候システムセミナー
国内外の研究者および大気海洋研究所メンバーによる研究発表を通じて、
気候モデリング、気候変動論などの知識の向上や
最新動向の把握を図るとともに、学生は研究の進め方、
まとめ方や発表の仕方を学ぶ
日時:金曜日 13:30-15:00
場所:東京大学柏キャンパス 総合研究棟270室
(*変更の場合もありますので、詳細は下記の予定をご確認ください)
今後の予定
青: 気候システムセミナー ;
緑: それ以外の内部向け関連情報
(2週間以上先の予定は変更になる可能性がありますので御了承下さい)
2024年10月29日(火) 15:00-16:30
松岸修平(大気海洋研究所特任研究員)
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Title: TBD
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Time: 15:00 - 16:30 on Oct. 29, 2024.
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Place: General Research Bldg. 2F room 270
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Abstract: TBD
2024年10月22日(火) 13:30-15:00
Prof. Samar Khatiwala (Waseda University)
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Title: Efficient spin-up of Earth System Models using sequence acceleration
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Time: 13:30 - 15:00 on Oct. 22, 2024.
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Place: General Research Bldg. 2F room 270
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Abstract:
The ocean and land carbon cycles plays a critical role in the climate system and are key components of the Earth System Models (ESMs) used to project future changes in the environment. However, their slow adjustment time also hinders effective use of ESMs because of the enormous computational resources required to integrate them to a pre-industrial quasi-equilibrium, a prerequisite for performing any simulations with these models. Here, a novel solution to this ``spin-up'' problem is shown to accelerate the equilibration of state-of-the-art marine and land biogeochemical models typical of those embedded in ESMs by over an order of magnitude. Based on a ``sequence acceleration'' method originally developed in the context of electronic structure problems, the new technique can be applied in a ``black box'' fashion to any existing model. Preliminary results suggest that the approach can also be applied to ocean physical model. The ability to efficiently spin-up ESMs would enable for the first time a quantification of major parametric uncertainties in these models, lead to more accurate estimates of metrics such as climate sensitivity, and allow increased model resolution beyond what is currently feasible.
2024年10月21日(月) 13:00-14:30
Jun Ying (大気海洋研究所客員研究員、State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography)
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Title: Effects of present-day SST biases on the projections of the
tropical Pacific SST warming pattern
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Time: 13:30 - 15:00 on Oct. 21, 2024.
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Place: General Research Bldg. 2F room 270
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Abstract:
Reliable projections of the tropical Pacific SST warming (TPSW) pattern
are key to understanding how the climate will change in response to
global warming. Most climate models that participate the phase five or
six of the CMIP project an El Nino-like warming pattern with a weakened
zonal SST gradient, yet such results are always questioned given that
there are various robust common biases when simulating the present-day
climate. In this talk, we will focus on how the two robust present-day
SST biases―the excessive cold tongue bias within the tropical Pacific
and the cold SST bias in the nearby tropical north Atlantic―affect the
projections of the future TPSW patterns in climate models. The emergent
constraints on the projected TPSW patterns by these two biases both
yield a more El Nino-like warming pattern with more weakened zonal SST
gradient than the original projections.
2024年10月9日(水) 10:00-11:30
横山千恵 (大気海洋研究所)
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Title: 衛星搭載降水レーダ観測による梅雨期の降水特性およびその将来変化予測
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Time: 10:00 - 11:30 on Oct. 9, 2024.
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Place: General Research Bldg. 2F room 270(*気候コロキウムと合同開催)
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Abstract:
雲降水システムに伴う非断熱加熱は、地球のエネルギー収支の重要な要素であると共に、様々な気象現象において重要な役割を果たしている。そのため、雲降水システムの実態解明は気候・気象システムの理解向上に不可欠である。同時に、雨がいかに降るかは我々の生活に直結する重要な情報でもある。発表者はこれまでに、衛星観測データを主に用いた解析から全球の降水特性や大規模場との関係に関する研究を行ってきた。本発表ではその中から、衛星搭載降水レーダ観測が捉えた梅雨期の雨の降り方に関する研究、及び一連の研究から得られた知見に基づいてマルチ気候モデル群の大規模場予測から推定された梅雨期降水特性の将来変化予測について紹介する。特に、その予測不確実性をもたらす大規模場について議論する。
2024年10月7日(月) 9:00〜17:00
修士論文に向けた中間発表会
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場所: 本郷キャンパス理学部1号館105号室(*本郷の大気海洋グループに合流して開催)
2024年8月28日(水) 15:30-16:30
Matt Luongo (Scripps Institution of Oceanography)
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Title: Subsurface Adjustment and Heat Transport Response of the Tropical Pacific to Hemispheric Energy Forcing
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Time: 15:30 - 16:30 on Aug. 28, 2024.
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Place: General Research Bldg. 2F room 270
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Abstract:
Changes in cross-equatorial ocean heat transport (OHT) damp hemispheric asymmetries in anomalous extratropical radiative forcing. Prior studies have suggested that these OHT changes occur due to wind-driven changes in the Indo-Pacific’s shallow subtropical cells (STCs) and buoyancy-driven changes in the deep Atlantic meridional overturning circulation. Here, I introduce a method of overriding surface ocean wind stress in a coupled global climate model (CGCM) to linearly partition the ocean’s response to anomalous extratropical forcing into surface buoyancy-driven and surface momentum-driven responses. In contrast with prior expectations, buoyancy-driven changes in the STCs are the primary driver of cross-equatorial heat transport in the Indo-Pacific’s response to Northern Hemisphere aerosol-like cooling. This buoyancy forced STC response arises from extratropical density perturbations that are amplified by the low cloud feedback in the Northeast Pacific marine stratocumulus regime.
While prior studies have explored the important role of surface ocean-atmosphere pathways in connecting the extratropics and tropics, I mechanistically explore the subsurface teleconnection (the so-called “oceanic tunnel”) further by using an ocean-only general circulation model forced by subtropical SST anomalies. Cooling in the Northeast Pacific low cloud deck dynamically adjusts the subtropical thermocline through baroclinic wave activity; within ten years the equatorial Pacific features a shoaled thermocline and La Nia-like cooling. This dynamically driven hemispheric temperature asymmetry drives an equatorially asymmetric subtropical cell adjustment, which transports heat to the cooled hemisphere and qualitatively matches our CGCM results. This overturning is a result of a basin-scale thermal wind response. I find similar equatorial responses when forcing is applied in the Northwest Pacific or the Southeast Pacific, highlighting the importance of wave activity for understanding this adjustment. These results provide a clearer understanding of how the tropical ocean adjusts to hemispheric energy forcing, which has important implications for climate sensitivity, tropical basin interactions, and historical observations of the tropical Pacific.
2024年7月25日(木) 13:30-15:00
Prof. Yi Huang (McGill University)
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Title: Dissecting climate and climate models with the aid of radiative kernels
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Time: 13:30 - 15:00 on Jul. 25, 2024.
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Place: General Research Bldg. 2F room 270
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Abstract:
Radiation is a crucial shaping factor of the Earth climate. Based on the global reanalysis data (ERA5), we have produced a new set of radiative kernels that can be used for diagnosing the radiation budgets at the Top-of-Atmosphere (TOA), surface and inside the atmosphere. In this talk, I will exemplify the use of the radiative kernels in different applications. The first case is an analysis of the "radiator fin" effect of the Arctic in the warming climate. This effect refers to a distinct positive trend of the Earth thermal radiation in the Arctic, which has been observed by the satellites in the past two decades. This effect acts to radiate excess heating accumulating in the climate system to the space during global warming. Using the aid of the band-by-band radiative kernels, we find that compared with other regions such as the tropics, the prominent thermal radiation trend in the Arctic results from a stronger surface and atmospheric warming and a less offsetting greenhouse effect of water vapor. The second case is a critical examination of the Global Climate Models (GCMs). Given the importance of the radiation budget, GCMs are often validated with regard to their simulated TOA radiation fluxes. Here we use the radiative kernels to diagnose the radiation biases in the CMIP6 GCMs. We find that many of them have a cold air temperature bias and a moist tropospheric humidity bias, which lead to considerable TOA radiation biases but are compensated by cloud-induced biases. These findings disclose that seemingly good radiation simulations can be due to compensating errors. This possibility can and should be checked with kernels during GCM development.
2024年7月24日(水) 10:00-11:30
高橋千陽(大気海洋研究所)
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Title: イベントアトリビューション迅速化のための新手法
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Time: 10:00 - 11:30 on Jul. 24, 2024.
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Place: General Research Bldg. 2F room 270(*気候コロキウムと合同開催)
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Abstract:
この10年ほど地球温暖化の加速とともに、全球的に熱波や豪雨が頻発しており、極端気象に対する人為的気候変動の影響を見積もるイベントアトリビューション(EA)の迅速化が求められている。従来のEAは、全球モデルや領域気候モデルによるダウンスケーリングによる大規模アンサンブル実験を実施した後で行うため、公表までに時間を要した。そこで、既存のデータのみを用いて、統計的にかつ迅速に気候変化影響を推定する新EA手法を開発した。日本の気象現象は、熱帯-中緯度域の海面水温偏差とそれに伴う大気循環場に影響を受ける事が知られているが、新手法は極端イベント発生時の海洋背景場の影響が考慮されている事が特徴である。発表では、新手法と日本の極端高温イベントへの適用例について紹介する。
2024年7月16日(火) 10:00-11:30
Prof. Graeme Stephens (Jet Propulsion Laboratory)
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Title: Tropical Deep Convection, Cloud Feedbacks and Climate Sensitivity
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Time: 10:00 - 11:30 on Jul. 16, 2024.
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Place: General Research Bldg. 2F room 270
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Abstract:
The lecture is concerned with how the diabatically-forced overturning circulations of the atmosphere, established by the deep convection within the tropical trough zone (TTZ), first introduced by Riehl and Simpson (1979), fundamentally shape the distributions of tropical and sub-tropical cloudiness and the changes to cloudiness as Earth warms. The talk first draws on analysis of a range of observations to understand the connections between the energetics of the TTZ, convection and clouds. These observations reveal a tight coupling of the two main components of the diabatic heating, the cloud component of radiative heating, shaped mostly by high clouds formed by deep convection, and the latent heating associated with the precipitation. Interannual variability of the TTZ reveal a marked variation that connects the depth of the tropical troposphere, the depth of convection, the thickness of high clouds and the TOA radiative imbalance. The study the examines connections between this convective zone and cloud changes further afield in the context of CMIP6 model experiments of climate warming. The warming realized in the CMIP6 SSP5-8.5 scenario multi-model experiments, for example, produces an enhanced Hadley circulation with increased heating in the zone of tropical deep convection and increased radiative colling and subsidence in the sub-tropical regions that then impacts low cloud changes and in turn the model warming response through low cloud feedbacks. The pattern of warming produced by models, also influenced by convection in the tropical region, also has a profound influence on the projected global warming.
2024年5月29日(水) 15:00-16:30
古関俊也(Bjerknes Centre for Climate Research)
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Title: Evaluating fine-scale ESMs for Southeast Asian Climate and Extreme
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Time: 15:00 - 16:30 on May 29, 2024.
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Place: General Research Bldg. 2F room 270
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Abstract:
Even state-of-the-art CMIP-class Earth system models (ESMs) still exhibit biases in simulating realistic climate state and these biases are source of uncertainties in climate prediction and projection. One of possible solutions could be a refinement of model’s resolution like High-ResMIP. Towards this direction, NextGEMS project (EU Horizon 2020) is developing European “storm-resolving” ESMs whose resolution is a range of 10km to a few km (atmosphere and ocean) globally.
This very fine resolution allows us to investigate climate, air-sea interaction, and extreme weather in marginal oceanic areas where common CMIP6 might have difficulty to resolve properly. This study assesses how 10km-resolution ESMs from NextGEMS project and other fine-resolution ESM can reproduce the climate and some extreme weather (wet and dry) in Southeast Asia that is related strongly to monsoon system, comparing to observation and some of CMIP6 ESMs.
In the seminar, I will focus more on winter monsoon season (Dec-Jan-Feb) and show some preliminary results of this verification.
(*セミナーは日本語で開催)
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問い合わせ先: 岡 顕(akira(at)aori.u-tokyo.ac.jp)、横山千恵(chie(at)aori.u-tokyo.ac.jp)
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