気候システムセミナー

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

• Title:TBD
• Time: 13:30-15:00 on Apr. 26, 2016.
• Place: General Research Bldg. 2F room 270.
• Abstract: TBD

• Title: The onset and withdrawal dates of rainy seasons over the eastern Indochina Peninsula and their relationship with ENSO
• Time: 15:00 - 16:30 on Feb. 5, 2016.
• Place: General Research Bldg. 2F room 270.
• Abstract: The onset dates of rainy season over the eastern Indochina Peninsula (8.5-23.5N, 100-110E) are objectively determined for individual years from 1958-2007 using the empirical orthogonal function (EOF) analysis. Two rainy seasons are determined by EOF1 and EOF2: the major summer rainy season (SRS) over most locations, and the autumn rainy season (ARS) occurring only along the easternmost coast of the Indochina Peninsula (ECI). Examination of the precursory signals associated with the early/late onsets of both SRS and ARS suggests that ENSO has a significant impact on their year-to-year variations. In La Nina years, the subsequent SRS tend to have early onsets. In contrast, advanced ARS onset generally occurs during an El Nino developing autumn with robust precursory signals in SST are observed only from mid-summer (July-August). However, no coherent correlation is found between the late onset and La Nina. Next, a significant delay in the withdrawal of the ARS (ARSW) along the ECI is detected since 1993. During 1979-92, the mean ARSW date was in early December, which is three pentads earlier than that during 1993-2006. The late ARSW in the recent epoch is characterized by the intensification and delayed equatorward retreat of the tropical easterlies, in response to the significant warm sea surface temperature (SST) in the western Pacific and cold SST in the central-eastern Pacific. Additionally, a distinct increase in the number of tropical cyclones (TC) passing through the southern South China Sea in 1993-2006 compared with 1979-92, which is related to a strengthening and more westward-extended sub-tropical high and a significant SST warming in the tropical western Pacific. These conditions may be attributed to a mean state change in the Pacific basin since the mid-to-late 1990s characterized by a grand La Nina-like pattern, which also results in the simultaneous advance of the Asian summer monsoon onset.

• Title: 集中豪雨に関する事例解析的・統計解析的研究
• Time: 13:30 - 15:00 on Feb. 5, 2016.
• Place: General Research Bldg. 2F room 270.
• Abstract: 現在，小職は気象研究所予報研究部において，集中豪雨の機構解明に関する研究に取り組んでいる． 従来からよく行われている事例解析に加えて，統計的な解析によるアプローチも試みている． 事例解析的研究として，2010年10月に発生した奄美豪雨の事例解析を行ったTsuguti and Kato (2014, JMSJ) を紹介する． 本研究では，豪雨を引き起こす主要因である大気下層の暖湿気塊に着目して解析を行った． その結果，元々は停滞前線の北側にあった乾燥した空気塊が， 奄美大島に近づくにつれて暖かい海面から多量の潜熱フラックスを受け取ることで， 十分に湿った空気塊へと変質(気塊変質)していたことが明らかになった． 時間が許せば，本事例以外にも，最近取り組んでいるいくつかの事例解析 (2013年8月の秋田・岩手県の大雨，平成27年9月関東・東北豪雨)について紹介する． 統計解析的研究として，津口・加藤 (2014, 天気)を紹介する． 本研究では，1995〜2009年の4〜11月に発生した集中豪雨事例を客観的に抽出し， それらの地域・季節特性を明らかにした． また，集中豪雨をもたらす総観規模擾乱，集中豪雨をもたらす降水系の形状に関する統計解析を行った． 後半では，最近取り組んでいるJRA-55を用いた 集中豪雨が発生する総観〜メソαスケールの環境場の統計解析について紹介する．

• 場所: 総合研究棟　4センター共用2階会議室 270

• Title: Impact of the Quasi-Biennial Oscillation on prediction of the Madden-Julian Oscillation
• Time: 13:30 - 15:00 on Nov. 30, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: The Madden-Julian Oscillation (MJO) during boreal winter is observed to be stronger during the easterly phase of the Quasi-Biennial Oscillation (QBO) than during the westerly phase, with the QBO at 50 hPa leading enhanced MJO activity by about one month. Using 30 years of retrospective forecasts from the POAMA coupled model forecast system, we show that this strengthened MJO activity during the easterly QBO phase translates to improved prediction of the MJO and its convective anomalies across the tropical Indo-Pacific region over the first month of the forecast. Although it is as yet unclear as to whether there is an impact of the QBO on the MJO during the forecast beyond simply being initialized with stronger MJO events during the easterly phase, the QBO appears to be an untapped source of subseasonal predictability that can provide a window of opportunity for improved prediction of global climate.

• Title: Seasonal Variation of Subtropical Precipitation and Hadley Circulation Associated with the Southern Annular Mode
• Time: 13:30 - 15:00 on Nov. 10, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: High-polarity SAM results in increased precipitation in high southern latitudes and decreased precipitation in midlatitudes as a result of the poleward shift of the midlatitude storm track. In addition, during summer, high SAM also results in increased rainfall in the subtropics and an expanded Hadley Circulation, but this subtropcial response is absent during winter. This seasonal variation of the response of subtropical precipitation and Hadley Circulation to the SAM is shown to be consistent with the seasonal variation of the eddy-induced divergent meridional circulation in the subtropics. The weak SAM-induced divergent meridional circulation in the subtropics during winter is attributed to the presence of the distinct wintertime subtropical jet: the anomalous equatorward propagating eddies that emanate from the higher mid-latitudes associated with the SAM break on both sides of the subtropical jet. A distinctive subtropical jet is less prominent during summer, so anomalous eddy activity produces a more narrowly confined region of momentum flux divergence in the subtropics, hence a stronger induced anomalous meridional circulation.

• Title: Untangling microphysical impacts on moist convection applying piggybacking methodology
• Time: 10:30 - 12:00 on Nov. 10, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: Formation and growth of cloud and precipitation particles (“cloud microphysics”) affect cloud dynamics and such macroscopic cloud field properties as the mean surface rainfall, cloud cover, and liquid/ice water paths. Traditional approaches to investigate the impacts rely on parallel simulations with different microphysical schemes or with different scheme parameters. Such methodologies are not reliable because of the natural variability of a cloud field that is affected by the feedback between cloud microphysics and dynamics. A novel modeling methodology, microphysical piggybacking, was developed to assess the impact of cloud microphysics on cloud dynamics and to separate purely microphysical effects from the impact on the dynamics. The main idea is to use two sets of thermodynamic variables driven by two microphysical schemes (or by the same scheme with different parameters), with one set coupled to the dynamics and driving the simulation, and the other set piggybacking the simulation, that is, responding to the simulated flow but not affecting it. We will discuss application of this methodology to cloud field simulations of shallow and deep convection. We will show that the methodology allows assessing the impact of cloud microphysics on cloud field properties with unprecedented accuracy. By switching the sets (i.e., the set driving the simulation becomes the piggybacking one, and vice versa), the impact on cloud dynamics can be isolated from purely microphysical effects. Applying single-moment and double-moment bulk microphysics, we will show that the new methodology documents a rather small indirect aerosol impact on convective dynamics for the case of scattered unorganized deep convection, but a significant microphysical effect.

• Title: Towards global large eddy simulation: super-parameterization revisited
• Time: 13:30 - 15:00 on Nov. 9, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: This talk will present the case for a global large eddy simulation model applying the super-parameterization (SP) methodology on massively parallel computers. I proposed SP about 15 years ago to improve representation of deep convection and accompanying cloud processes in large-scale models of weather and climate. The main idea behind SP is to embed---in all columns of the large-scale model with a horizontal gridlength of the order of 100 km---copies of a two-dimensional nonhydrostatic convection-permitting small-scale model with about 1 km horizontal gridlength and periodic lateral boundary conditions, and to couple them with the outer model. This methodology can be expanded by applying a high-spatial-resolution three-dimensional SP model, essentially a large-eddy simulation model, and by embedding its copies in all columns of a large-scale model with the horizontal gridlength in the range of 10 to 50~km. The outer model will then simulate processes down to the mesoscale (e.g., organized convection) and small-scale processes (e.g., boundary layer turbulence, convective drafts) will be simulated by LES models. Although significantly more expensive than the traditional SP, the SP LES is ideally suited to take advantage of parallel computers (e.g., applying GPU technology) because of the minimal communication between LES models when each processor runs a single LES model. Additional benefits of such a methodology will be discussed, and a simple computational example will be presented.

• Title:A Modeling Study on Coupling between Westerly Wind Events and ENSO (西風イベントとENSOの結合に関するモデル研究)
• Time: 14:00-16:00 on Oct. 16, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: 西風イベント(WWE)は西部・中央熱帯太平洋において強い海上の西風偏差が数日から数週間持続する現象であり，エルニーニョ現象のきっかけとなることがある．WWEとエルニーニョ・南方振動(ENSO)との関係は観測および数値実験によって調査されてきた．WWEに対する熱帯海面水温(SST)の応答は背景場や年々変動の摂動に依存することが示されてきたが，大気海洋結合モデルの背景場のバイアスが結合系の季節性の役割の評価を困難にしている．また，簡素なモデルによってWWEがENSOの多様性をもたらしうることが示されているが，手法やモデルパラメータへの依存性は明らかでない．本研究では，WWEに対する大気海洋結合系の応答のWWE発生の時期および経度への依存性と，WWEとENSOの結合系におけるWWEの背景場依存性がENSOに果たす役割を数値モデルによって調査した． まず，大気海洋結合大循環モデルMIROC5.2を用いた初期値アンサンブル実験により，様々な時期および経度に与えられる理想化された単一のWWEに対する結合系の変動を調べた．MIROC5.2の熱帯降水と温度躍層は観測される季節性をよく再現する．実験の結果，WWEに対する結合系応答は温度躍層と大気循環(特にITCZ)の両方の季節性に強く依存するためにWWEに伴う熱帯太平洋の昇温は様々であった．5月に与えるWWEがITCZの南下を伴うことによって東部赤道太平洋で効率的な昇温をもたらすことが分かった．この結果と観測データを組み合わせて，熱帯太平洋の昇温に効果的なWWE発生の時期および経度の組み合わせを示した． 次に，再解析データを用いてWWEの背景場および年々変動への依存性を調査した．WWEはSSTが28.5℃を超える暖水域上(特に暖水域東端付近)で発生し，Nio4領域でのSST偏差が正の場合により発生しやすいことを示した．WWEの反対符号の現象である東風イベント(EWE)との比較を行ったところ，その発生条件はWWEとよく似ていることと，両イベントに対して中心経度から60度以上西に離れた対流偏差が東西風の強化に貢献していることが示された．一方，発生機構の非対称性がEWEの発生頻度を相対的に小さくする．WWEの観測的特徴に基づき，簡素な大気海洋結合モデルにWWEをパラメタライズし，WWEの背景場および年々変動への依存性がモデル内の年々変動へ与えるインパクトを調査した．規則的なENSOを表現するモデルにおいて，WWEを西太平洋にランダムに与えることで不規則かつ異なる空間構造をもつENSO(中央太平洋および東部太平洋型エルニーニョ)が得られることを確認した．WWEの背景場依存性は，Nio4 SST偏差に依存する発生頻度と，太平洋暖水域の拡大に依存発生経度に分けられるが，それらがENSOの多様性に対して異なる働きをすることを，大気海洋結合の強さを変えた複数の実験によって示した．

• 場所: 総合研究棟　4センター共用2階会議室 270

• Title: How much rainfall extremes associated with Typhoon Morakot (2009) can be attributable to anthropogenic influences?
• Time: 10:30 - 12:00 on Oct. 8, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: More than 2000 mm rainfall occurred over southern Taiwan when a category 1 Typhoon Morakot passed through Taiwan in early August 2009. Entire village and hundred of people were buried by massive mudslides induced by record-breaking precipitation. Whether the past anthropogenic warming played a significant role in such extreme event remained very controversial. On one hand, people argue it's nearly impossible to attribute an individual extreme event to global warming. On the other hand, the increase of heavy rainfall is consistent with the expected effects of climate change on tropical cyclone. To diagnose possible anthropogenic contributions to the odds of such heavy rainfall associated with Typhoon Morakot, we adapt an existing event attribution framework of modeling a "world that was" and comparing it to a modeled "world that might have been" but in the absence of historical anthropogenic drivers of climate. One limitation for applying such approach to high-impact weather system is that it requires models capable of capturing the essential processes lead to the studied extremes. Using a cloud system resolving model that can properly simulate the complicated interactions between tropical cyclone, large-scale background, topography, we first perform the ensemble "world that was" simulations using high resolution ECMWF YOTC analysis. We then re-simulate, having adjusted the analysis to "world that might have been conditions" by removing the regional atmospheric and oceanic forcing due to human influences estimated from the CMIP5 model ensemble mean conditions between all forcing and natural forcing only historical runs. Thus our findings are highly conditional on the driving analysis and adjustments therein, but the setup allows us to elucidate possible contribution of anthropogenic forcing to changes in the likelihood of heavy rainfall associated Typhoon Morakot in early August 2009.

• Title: Weakened El Nino Predictability in the Early 21st Century
• Time: 13:30 - 15:00 on Oct. 7, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: Predictive skill for El Nino in the tropical eastern Pacific declined sharply in the early 21st century relative to what was achieved in the late 20th century despite ongoing improvements of forecast systems and initial conditions. This decline in skill coincided with a reduction of El Nino variability in the eastern Pacific together with a shift in Pacific climate to a stronger Walker circulation that has previously been associated with the hiatus in global warming. Using seasonal forecast sensitivity experiments, we show that the shift to a stronger Walker circulation at the end of the 20th century acted to weaken the ocean-atmosphere feedbacks that amplify El Nino thus resulting in weaker variability that is less predictable. Anticipating future changes in El Nino predictability is an outstanding challenge because prediction of decadal variations of Pacific climate has not been demonstrated and no consensus has yet emerged about impacts of anthropogenic climate change on El Nino variability

• Title: Intraseasonal variability in the Indian Ocean and Maritime Continent
• Time: 13:30 - 15:00 on Oct. 2, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: The dynamics and predictability of the tropical intraseasonal variability (TIV) is discussed based on the following analyses. A composite of low-troposphere moisture (qL) budget is performed based on 22 MJO events with strong magnitude and clear propagation in Nov.-April, 1982-2011. The evolution of the MJO budget within 25-90 day filtered band is analyzed in four stages: suppressed, cloud developing, convective, and decaying, reference to equatorial Indian Ocean (EIO, 30-60E, 10S-10N) that correspond to phases 567, 81, 2, and 34, respectively according to RMM indices. In the 1st stage, qL over EIO moistens primarily due to surface evaporation/shallow convection, and followed by horizontal zonal advection by divergent easterlies in response to EIO cooling/Maritime Continent (MC) heating. In the 2nd stage, qL over EIO approaches maximum with moistening and drying tendencies to its east and west and the MC enters the suppressed stage. The MC cooling induces easterlies over EIO advecting moisture westward, and convection developing over western IO causes decreasing q. In the 3rd stage, MJO convection resides over EIO and MC is in the suppressed phase. Zonal advection by convergent flow over EIO causes advective drying over WIO and moistening over MC, and deep convection causes drying over EIO. In the 4th stage, MJO convection moves from IO to MC, zonal advection by westerly over EIO causes a wide spread drying in qL. A similar analysis is performed for the two MJOs over the IO during Dynamics of the MJO (DYNAMO). While the overall results are consistent with the 22-event composite, the two MJOs exhibit different budget balances in pre-moistening stage from the suppressed phase to cloud developing phase when low-frequency vertical motion is downward in MJO1 but upward in MJO2. The corresponding drying and moistening are balanced by negative Q2 (re-evaporation in non-raining cloud) in MJO1 and positive Q2 in MJO2. The advection by high-frequency disturbance acts as a diffusion process. The above analysis is utilized for a modeling analysis using the Model for Prediction Across Scales (MPAS). The MPAS is collaboratively developed, primarily by NCAR and LANL/DOE based on global nonhydrostatic framework using Voronoi Meshes. The MPAS reasonably simulates the overall evolution of the moisture field of the two MJOs but with less organized cloud clusters and weaker propagation. The performance warrants a further application of the model to study the issues like initiation and propagation processes of the MJOs.

• Title:
  (1) 13:30-14:50 岡崎淳史「水同位体大気陸面結合モデルの開発および気候プロキシとの比較」
  (2) 15:00-16:20 魏忠旺 「Study on atmosphere and terrestrial water and energy circulation processes by using stable water isotopes」
  
• Time: 13:30-16:20 on Sep. 28, 2015.
• Place: General Research Bldg. 2F room 270.

• Title: Sub-regional variation in convection responsible for East Asia summer monsoon precipitation
• Time: 13:30 - 15:00 on Aug. 25, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: In this study, the spatial and diurnal variation of storm height in the East Asia summer monsoon region is examined using 13-year Tropical Rainfall Measuring Mission Precipitation Radar data. Precipitating storms are classified as shallow (<5km), intermediate (5-10km), and deep (>10km) depending the height. Although the shallow storm is basically the most frequent, four different regimes are identified to characterize the region: the continental (CT) shallow regime over inland China with elevated terrain, the CT deep over the Chinese Plain, the coastal (CS) intermediate over the East China Sea and South Sea of Korea, and the CS shallow over the south coastal area of Japan. This study has also analyzed quantitative contribution of shallow, middle, and deep rain to total summer rainfall and the diurnal variability. Despite of more frequent occurrence of the shallow convection, surface rain rate is mostly contributed by intermediate convection. The bimodal morning and late evening peaks in the two CT regimes are contributed to the increased intermediate and deep storms, respectively. Over the two coastal sea regimes, the rainfall and all three kinds of storms simultaneously increase in the morning. Due to the continental-scale land-sea contrast, the large-scale atmospheric circulation that is favorable for invigorating cloud and precipitation processes with increased shallow and intermediate storms in the morning. Given the primary role of intermediate (less deeper) convection to total rainfall accumulation, this study highlights that the monsoon precipitation has distinctive sub-regional variation over Korea, Japan, and China, thereby providing unique differences in the rainfall amount, intensity, and the diurnal mechanism.

• Title: EnKF Assimilation of GOES-R and Himawari-8 All-sky Infrared Brightness Temperature for the Analysis and Forecast of Tropical Cyclones (台風の予測向上に向けた、EnKFを用いたGOES-RおよびHimawari-8の赤外輝度温度同化)
• Time: 10:30 - 12:00 on Jul. 23, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: An ensemble-based data assimilation system is used to assess the impact of assimilating satellite infrared radiance data in both clear and cloudy skies on the forecast of tropical cyclones. The current study builds on recent improvements in tropical cyclone forecasts via assimilation of high-resolution ground-based and airborne Doppler radar observations that are available around coastlines or for select Atlantic basin storms within reach of reconnaissance aircraft. The new generation geostationary satellite infrared radiance data, including those from the Advanced Himawari-8 Imager (AHI) on the Geostationary Meteorological Satellite that launched in October 2014 and the Advanced Baseline Imager (ABI) on the Geosynchronous Operational Environmental Satellite (GOES) that will be launched in 2016, have or will have near global coverage at all times with high spatial and temporal resolution. GOES-ABI and GMS-AHI will provide two times higher spatial and temporal resolution radiance data than the satellites currently in orbit. Both contain 10 infrared channels with 2 km x 2 km spatial resolution with images produced every 15 minutes. The assimilation of such high-resolution satellite observations in both clear and cloudy skies is challenging given their strong non-linear relationships to the underlying model fields, the general lack of effective quality control on them, the need to apply bias corrections to them, and the necessity of data synthesizing and thinning for their application to regional scale numerical weather prediction. These difficulties are especially relevant to the cloudy radiances. For the current study we couple the Community Radiative Transfer Model (CRTM) to the ensemble Kalman filter (EnKF) data assimilation system developed at Penn State University (PSU) and built around the Weather Research and Forecasting model (WRF). This new framework, together with our assimilation strategies that include superobbing and effective data quality control, enables us to directly assimilate multiple channel brightness temperatures with high temporal and spatial resolution into the EnKF. The impact of assimilating brightness temperatures from these new advanced imagers is assessed through both examining the dynamical covariance between the satellite radiances and the state variables estimated from an ensemble and performing extensive observing system simulation experiments (OSSEs) for Hurricane Karl (2010). Preliminary experiments show promising improvements in hurricane initialization and forecasting via assimilation of these next generation brightness temperatures. Ongoing research also explores the effectiveness of using the successive covariance localization (SCL) technique of Zhang et al. (2009 MWR), the impact of assimilation window length and the observation density, observational error covariance. We will be also exploring the impact of assimilating the satellite radiance in comparison to (and in addition to) other in-situ and remotely sensed observations.
  アンサンブルカルマンフィルターを用いた全空における赤外輝度温度の同化が、 台風の予測・解析に対してどの程度貢献するかについての発表を行う。特に、新 世代の衛星である2014年10月に打ち上がったHimawari-8および2016年3月に打ち 上げ予定のGOES-Rの影響について調査した。これら新世代の衛星は半球規模の撮 影範囲と高い解像度を持っており、赤外画像データは毎10~15分、解像度2kmで利 用可能である。これら全空の赤外輝度温度のデータ同化は、その強い非線形性の 対処、効果的なクオリティコントロール、バイアス補正、データ抽出などが必要 とされ、非常に困難であった。 本研究ではCommunity Radiative Transfer Model (CRTM) をPSU WRF-EnKFシステ ムにカップリングし、全空の赤外輝度温度観測データを直接同化した影響につい て調査している。本システムは新世代の衛星による高解像度の観測データを複数 チャンネル同化することができ、新たな衛星の高い機能をよく引き出すことが可 能となった。これら観測データを同化したインパクトについて、共分散構造の解 析と、observing system simulation experiments (OSSEs) のフレームワークを 用いて示す。再現された台風は、目の雲域や風速場の非軸対象構造の特徴を捉え るなど、赤外輝度温度同化の有用性が端的に示された。

• Title: Estimating relative importance of weather and climate modes for Antarctic sea ice variability
• Time: 15:00 - 16:30 on Jul. 13, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: Cross-spectral analysis shows that geopotential height and Antarctic sea ice extent are most coherent at periods between about 20 and 40 days. One of the most dominant meteorological variabilities in this period range is associated with Rossby waves that are excited by weather dynamics, orography, and heat sources. Rossby waves explain 50-70 percent of intraseasonal variability of Antarctic sea ice during the ice maximum season. These Rossby waves are not correlated with the El Nio Southern Oscillation (ENSO) nor the Southern Annular Mode (SAM), which have received much attention for explaining Antarctic sea ice variability. Lag regression analysis shows that Rossby waves move slowly eastward following the background flow. The southerly (northerly) wind anomalies push sea ice northward (southward) and provide cold (warm) advection. On longer time scales, ENSO and SAM become important for sea ice, but Rossby modes also share comparable variance on longer time scales. If we remove the influence of the most important climate mode from the sea ice extent time series for a region, the positive sea ice trends become insignificant at 95 %. Therefore, the positive trend may be explained by superposition of anthropogenic forcing and natural variability in Indian Ocean, where the most important climate mode (SAM) has a human-induced trend. On the other hand, the ice trend might be produced purely by natural variability in the Ross Sea, where the most important atmospheric variability (ENSO) does not have a significant trend. This is possible if ice responds as a low-pass filter of meteorology.

• Title: ENSO/Annual Cycle interactions and their impact on Indo-Pacific climate
• Time: 16:00 - 17:30 on Jun. 18, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: Nonlinear interactions between the El Nio-Southern Oscillation (ENSO) and the Western Pacific warm pool annual cycle generate an atmospheric combination mode (C-mode) of atmospheric circulation variability. We demonstrate that C-mode dynamics are responsible for the development of an anomalous low-level North-West Pacific anticyclone (NWP-AC) during El Nio events. The NWP-AC is embedded in a large-scale meridionally anti-symmetric Indo-Pacific atmospheric circulation response and has been shown to exhibit large impacts on the Asian Monsoon system. In contrast to previous studies, we find the role of air-sea coupling in the Indian Ocean and North-West Pacific only of secondary importance for the NWP-AC genesis. Moreover, the NWP-AC is clearly marked in the frequency domain by near-annual combination tones, which have been overlooked in previous Indo-Pacific climate studies. Furthermore, we hypothesize a positive feedback loop involving the anomalous low-level NWP-AC through El Nio and C-mode interactions: the development of the NWP-AC as a result of the C-mode acts to rapidly terminate El Nio events. The subsequent phase shift from retreating El Nio conditions towards a developing La Nia phase terminates the low-level cyclonic circulation response in the Central Pacific and thus indirectly enhances the NWP-AC and allows it to persist until boreal summer. Anomalous local circulation features in the Indo-Pacific (such as the NWP-AC) can be considered a superposition of the quasi-symmetric linear ENSO response and the meridionally anti-symmetric annual cycle modulated ENSO response (C-mode). We emphasize that it is not adequate to assess ENSO impacts by considering only interannual timescales. C-mode dynamics are an essential (extended) part of ENSO and result in a wide range of deterministic high-frequency variability. A general framework for this frequency cascade will be discussed.

• Title: Development of the aerosol assimilation system for the NICAM-Chem
• Time: 13:30 - 15:00 on Jun. 5, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: The aerosol optical properties simulated by the NICAM-Chem are evaluated using the space-based and ground-based observations. For each aerosol species, the mean AOT is within the range of the AeroCom models. For the 3-year mean AODs and AEs for all sites show the correlations between model and AERONET of 0.753 and 0.735, respectively, and 82.1% of the modeled AODs agree within a factor of two with the retrieved AODs. The primary model deficiency is an underestimation of fine mode aerosol AOD and a corresponding underestimation of AE over pollution region. The effects of cloud on aerosol model evaluation are also considered with the MODIS cloud observations. The differences between clear-sky and all-sky AODs are larger over polluted regions. The aerosol assimilation system for the NICAM-Chem is further developed to improve the model performances. Assimilation leads to significantly positive effect on the simulated AOD field, improving agreement with all of the 12 AERONET sites over the Eastern Asia based on both the correlation coefficient and the root mean square difference (assimilation efficiency). Meanwhile, better agreement of the ngstrm Exponent (AE) field is achieved for 8 of the 12 sites due to the assimilation of AOD only.

• Title: 高解像度非静力学モデルを用いた熱帯低気圧の温暖化による構造変化に関する研究
• Time: 10:30-12:00 on May. 8, 2015.
• Place: General Research Bldg. 2F room 270.

• Title: "What causes Dansgaard- Oeschger (and H) events?"
• Time: 13:30 - 14:30 on Apr. 30, 2015.
• Place: General Research Bldg. 2F room 270.

• Title: Cloud microphysics and climate: Use of satellite observations for advancing climate modeling
• Time: 13:30 - 15:00 on Apr. 24, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: Cloud microphysics is a key component in global climate models and is also an important pathway through which atmospheric aerosols influence the cloud and climate. This so-called aerosol indirect effect is one of the most uncertain factors in climate projection. Recent progresses in satellite observations and numerical modeling offer a unique opportunity to study cloud microphysics and its implication for global climate. In this talk, I would like to highlight recent studies by myself and colleagues who have used satellite observations to obtain new insight into microphysical processes of warm clouds on the global scale and have exploited the observation-based information to evaluate the process representations in climate models. This “process-oriented” approach for model evaluation was applied to some of the CMIP5 climate models as well as to cloud-resolving models to identify their key biases in representation of cloud microphysics. This approach was also combined with a theoretical analysis based on a simple one-dimensional model to attribute the global model biases to uncertain parameters in formulation of the parameterization. The analyses offer a novel way to constrain some of the uncertain parameters, which have often been regarded as “tunable knobs” in climate models. The implication of such a process-based model constraint for climate projection will also be discussed to expose a new challenge for climate modeling.

• Title: Modeling Microclimates and Projecting Climate Change in Hawaii
• Time: 13:30 - 15:00 on Apr. 10, 2015.
• Place: General Research Bldg. 2F room 270.
• Abstract: Hawaii is located in a dominant trade wind meteorological regime. The trade wind regime covers a very significant fraction of the globe, but few people live in this zone. The densely populated Hawaiian islands are a notable exception. While Hawaii is known for its pleasant weather, climate variations and climate change can present significant challenges to the residents. Sea level rise, beach erosion and threats to coral health are all familiar issues for the State. On the terrestrial side as well there are significant concerns including impacts of droughts on fresh water resources and impacts of global warming on plant and wildlife habitat. In this talk I will present some results from an ongoing initiative to project future climate changes in Hawaii using very fine resolution regional models. The interaction of the large scale flow with the very steep and fine scale topography on the main Hawaiian islands presents particular challenges, and I will discuss the current state of our simulations and our plans for future work at IPRC.

• 2014年度
• 2013年度
• 2012年度
• 2011年度
• 2010年度
• 2009年度
• 2008年度
• 2007年度
• 2006年度
• 講演資料（所内限定）