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: Retrieving Aerosol Optical Thickness and Altitude of Asian Dust from AIRS IR Hyperspectral Measurments
• Time: 13:30-15:00 on Mar. 28, 2013.
• Place: General Research Bldg. 2F room 270.
• Abstract: Aerosol optical thickness (AOT) and effective height (zdust) of Asian dust were retrieThe potential applicability of IR hyperspectral measurements to dust monitoring, that was demonstrated and substantiated by the ANN results, brings in a possibility of developing a physical retrieval algorithm for Asian dust. In doing so, the fast Radiative Transfer for Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder (RTTOV) model (version 9.3) was implemented with an updated dust-size distribution and surface emissivity for better simulating the dust effect on top of atmosphere radiances. Also included were the refractive indices giving better Asian-dust simulation results, in comparison to AIRS-measured TBs. Adopting a one-dimensional variational (1DVAR) approach embedded with the implemented RTTOV model, a physical model has been developed for retrievals of Asian dust AOT and effective height. Results show that AIRS-derived IR AOTs are well correlated with the MODIS visible (VIS) AOTs, with correlation coefficients of 0.77-0.96. Effective dust heights also agree well with dust heights derived from CALIPSO backscattered reflectivity profiles. In conclusion, AOT and the effective height of Asian dust can be retrieved from IR hyperspectral measurements with accuracies comparable to MODIS AOT and CALIPSO dust height. Since those parameters can be retrieved on a two-dimensional basis in both day and night, IR hyperspectral sounder measurements can significantly improve dust forecasting through dust monitoring and data assimilation.

• Title: How well can we tell about the past and future climate using climate models?
• Time: 14:00-16:00 on Mar 14, 2013.
• Place: General Research Bldg. 2F room 270.
• Title of talk:
  Modelling the Last Deglaciation: How well can we simulate the past climates? (Paul Valdes, Bristol University, UK)
  Development of an earth system model of intermediate complexity and modeling the glacial climates (Andrey Ganopolski, PIK, Potsdam, Germany)
  Climate Risk Management in the Anthopocene (Klaus Keller, Penn-State University, USA)
  

• Title:
  (1) 北米の陸域水循環における10年規模の予測可能性(近本喜光)
  (2) アリューシャン低気圧の変動に対する北太平洋海洋生態系の10年規模応答と予測可能性(近本めぐみ)
• Place: General Research Bldg. 2F room 270.
• Time: 15:30-17:30 on Mar 8, 2013.
• Abstract:
  (1)北米の陸域水循環における10年規模の予測可能性について、NCAR の地球システ ムモデル (CESM)をもちいて調べた。北米における降水と土壌水分に対して主成 分解析を行ったところ、モデルは主要な変動モードとして、南北対称なシーソー パ ターンを示した。このうち、降水変動はホワイトノイズとして振る舞うもの の、土壌水分には10年規模の低周波変動が卓越していた。モデルのコント ロー ルランをもとに、200年間の予測実験を行ったところ、降水変動の予測可能性は1 年未満であるのに対し、土壌水分の予測可能性は深さに依存 し、全水分貯蔵量 には最大で10年規模の予測可能性があった。これらのことは、たとえ陸域の降水 量が予測できないとしても、土壌水分には10年規 模の予測可能性があることを 示唆している。さらに、CESMを用いることで、北米における土壌水分の10年規模 の予測が森林火災のリスク評価に適 応できることを本研究は示唆する。
  (2)北西太平洋海域は栄養塩が豊富で、植物プランクトンの生産性が高く、世界3大 漁場の一つとして知られている。一方で、北太平洋は、冬期にアリュー シャン 低気圧が発達し、1年以内の短周期大気擾乱が卓越する海域でもある。本研究 は、この短い時間スケールのアリューシャン低気圧の変動に対し、 北太平洋の 海洋生態系がどのように応答し、また予測可能性があるのかについて、地球シス テムモデルCESMを用いて調べた。500年のコントロー ルランでは、アリューシャ ン低気圧の変化に対し、海洋表層栄養塩や植物プランクトンの生物量は2~4年程 度の相関が見られた。アリューシャン低気 圧の発達（弱化）は、エクマン湧昇 の増加（減少）を伴うが、これらの変動は1年程度で、海洋生態系の長期変動を 説明できない。一方、海洋表層の東 西流は、大気擾乱に伴い、2、3年程度変動 が持続する。これらの結果は、短い時間スケールの大気擾乱に対し、海洋循環場 と栄養塩などのトレーサー が数年規模のメモリをもつことを示している。今回 の発表では、CESMの結果および観測データとのモデル評価を紹介する。

• Title: Statistical Evidence for the Natural Variation of the Central Pacific El Nino
• Time: 15:00-16:30 on Feb. 1, 2013.
• Place: General Research Bldg. 2F room 270.
• Abstract: Extensive studies claimed that the central equatorial Pacific (CP) El Nino has occurred more frequently and strongly than the eastern equatorial Pacific El Nino in recent years. To explain this phenomenon, spatial patterns and principal component time series from several sea surface temperature (SST) data sets in the tropical Pacific are analyzed for the period of 1951-2010. Cyclostationary empirical orthogonal function analysis separates two modes of SST variability, which explain about 50% and 10% of the total SST variability, respectively. Their spatial and temporal patterns are similar among the different SST data sets. The first mode captures the typical El Nino pattern, while the second mode is a dipole pattern in the tropical Pacific. The two modes are, by definition, uncorrelated over the analysis period but are in phase since the late 1990s; superposition of the two modes results in a significant warming in the CP region, which is a potential explanation for a more frequent occurrence of the CP El Nino in the recent decades. Similar analysis is conducted based on the 500 year data from the Geophysical Fluid Dynamics Laboratory Climate Model version 2.1 under the preindustrial condition. The result is generally consistent with the observations yielding occasional in-phase relationship between the two modes. Thus, it cannot be ruled out that a more frequent occurrence of the CP El Nino in recent years is a natural feature of the equatorial climate system. Our new results on ENSO properties in MRI-CGCM3 will be also presented.

• 場所: 総合研究棟　4センター共用2階会議室 270

• Title: The CALIPSO Mission: What we are learning from global active profiling of aerosols and clouds
• Time: 13:30-15:00 on Nov 30, 2012.
• Place: General Research Bldg. 2F room 270.
• Abstract: The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission was developed as a joint project between NASA and the French space agency CNES to provide active lidar profiling of aerosols and clouds. The satellite also carries a multichannel infrared radiometer, allowing synergistic lidar-infrared cloud retrievals. Launched in April 2006, CALIPSO has now acquired more than 6 years of global observations. Observing aerosols and clouds with high vertical resolution, from the marine boundary layer to the stratosphere, CALIPSO is providing a new view of the global atmosphere. This talk will review some of the results coming from CALIPSO.

• (1) 13:30-15:00 Dr. Hugh Morrison
  Title: Impact of cloud microphysics on moist deep convection
  (2) 15:15-16:45 Prof. Greg Tripoli
  Title: An Alternative Formulation of Inertial Available Kinetic Energy for Application to Tropical Cyclones
• Time: 15:15-16:45 on Nov 26, 2012.
• Place: seminar room 219 (another AORI building)
  
• Abstract
  (1) Dr. Morrison's talk :
  With increasing use of high resolution (convection-permitting) models for numerical weather prediction and climate simulation, microphysics has moved to the forefront in terms of physical parameterizations. This is because without the use of traditional convection parameterizations in these models, microphysics is directly coupled to the convective dynamics. An overview of current approaches for representing microphysics will be given, as well as recent efforts to improve parameterizations. Impacts of microphysics in "cloud-resolving" model simulations of deep convection will be described. These sensitivities will be also be compared to sensitivities arising from other key aspects, such as horizontal grid resolution.
  (2) Prof. Tripoli's talk:
  The impact of outflow-level inertial stability on deep convection has been a subject of interest for several decades Kuo (1954), Arakawa and Schubert (1974), Emanuel (1979), Nehrkorn (1986), Seman (1994). These studies showed that the strength that a mescoscale circulation supporting convection can attain is tied to the outflow resistance, which is largely regulated by inertial stability. The formulation of IAKE proposed by Mecikalski, and Tripoli (1998), was designed to quantify the impact of outflow-level inertial stability on convection intensity. For instance, positive IAKE implies that the sheer between outflow momentum (carried up in the updraft from below) and environmental momentum is inertially unstable and energy is released as outflow expands actually helping grow the whole mesoscale circulation. There has also been a number of studies, beginning with Emanuel and Rotunno (1986), Merrill and Velden (1996), Rappin, Morgan, and Tripoli (2010) showing that the outflow resistance has a major impact on tropical cyclone genesis and strength. In fact, Emanuel and Rotunno showed that the work performed by the Carnot engine of a tropical cyclone, is used for two purposes: (1) to fight surface friction and (2) to perform work against outflow resistance. IAKE then, quantifies the work needed to building outflow, and so directly impacts the ability of a TC to grow or maintain intensity. Sears and Velden (2011) applied the IAKE concept to convection within a tropical cyclone and successfully improved the prediction of TC genesis. The ideas of Mecikalski and Tripoli, however, were designed for individual cumulus featuring a single updraft stream having outflow of the genesis stage, they are not as typical of a maturing stage of a TC, where convection forms in mesoscale bands or an eyewall. Moreover, the long lifetimes of a TC allow the TC to significantly alter its own outflow environment out to large distances. In this talk, a new alternate formulation of an IAKE diagnostic parameter is presented that is more adequately designed for the tropical cyclone problem.

• Title: Development of the synthetic GPM simulator: construction of GV-constrainted CRM database
• Time: 13:30-15:00 on Nov 22, 2012.
• Place: General Research Bldg. 2F room 270.
• Abstract: The next-generation Global Precipitation Measurement (GPM) mission will offer a global view of precipitation systems and enable accurate measurement of frozen precipitation and light rainfall as well as tropical rainfall. We developed the synthetic GPM Simulator that integrates in-situ observations, a cloud-resolving simulation, and satellite simulators to synergistically support development of the GPM precipitation algorithms. This presentation introduces overall results of cloud resolving simulations to construct the testbed database for three field campaigns of the ground validation (GV) program: C3VP, LPVEx and MC3E. Inland snowstorm, synoptic-scale mixed-phase stratiform rain and meso-scale convective systems with high rainfall rate are focused on for particular precipitation events during these field campaigns.

• Title: Evaluation of Surface Flux Parameterizations with Long-Term ARM Observations
• Time: 13:30-15:00 on Nov 14, 2012.
• Place: General Research Bldg. 2F room 270.
• Abstract: Surface momentum, sensible heat and latent heat fluxes are critical for atmospheric processes such as clouds and precipitation, and are parameterized in a variety of models ranging from cloud-resolving models to large scale weather and climate models. However, direct evaluation of the parameterization schemes for these surface fluxes is rare due to limited observations. This study takes advantage of the long-term observations of surface fluxes collected at the Southern Great Plains site by the Department of Energy Atmospheric Radiation Measurement program to evaluate the six surface flux parameterization schemes commonly used in the Weather Research and Forecasting (WRF) model and three US global climate models (GCMs). The unprecedented 7 year long measurements by the Eddy Correlation (EC) and Energy Balance Bowen Ratio (EBBR) methods permit statistical evaluation of all the six parameterizations under a variety of stability conditions, diurnal cycles and seasonal variations. The statistical analyses show that the momentum flux parameterization agrees best with the EC observations, followed by latent heat flux, sensible heat flux, and evaporation ratio/Bowen ratio. The overall performance of the parameterizations depends on atmospheric stability, best under neutral stratification and deteriorating toward both more stable and more unstable conditions. Further diagnostic analysis reveals that in addition to the parameterization schemes themselves, the discrepancies between observed and parameterized sensible and latent heat fluxes may stem from inadequate use of input variables such as surface temperature, moisture availability and roughness length. The results demonstrate the need for improving land-surface models and measurements of surface properties that permits evaluation of full land surface models.

• Title:北極圏における陸域水循環過程の解明に向けた陸面モデルの高度化に関する研究
• Time: 16:30-18:00 on Nov. 2, 2012.
• Place: General Research Bldg. 2F room 270.

• Title:Dust optical properties over the Sahara and Asia inferred from Moderate Resolution Imaging Spectroradiometer
• Time: 14:30-16:00 on Nov. 2, 2012.
• Place: General Research Bldg. 2F room 270.
• Abstract: There is a great deal of uncertainty surrounding the role of mineral dust aerosols in the earth’s climate system. One reason for this uncertainty is that the optical properties of mineral dust, such as its single scattering albedo (the ratio of scattering to total extinction), are poorly understood because ground observations are limited to several locations and the satellite standard products are not available due to the excessively bright surface of the desert in the visible wavelength. We develop a method to estimate the spatial distributions of the aerosol single scattering albedo (ω0) and optical depth (τa), with daily 1 degree latitude and 1 degree longitude resolution, using data from Moderate Resolution Imaging Spectroradiometer (MODIS), as well as model simulations of radiative transfer. This approach is based on the “critical surface reflectance” method developed in the literature, which estimates ω0 from the top of the atmospheric radiance. We confirm that the uncertainties in our estimation of ω0 and τa are suitably minor and that the characteristic spatial distributions estimated over the Sahara and Asia are significant. The results for the Sahara indicate good correlation between ω0 and the surface reflectance and between ω0 and τa. Therefore, ω0 is determined mainly by the mineral composition of surface dust and/or the optical depth of airborne dust in the Sahara. On the other hand, the relationships between ω0, τa, and the surface reflectance are less clear in Asia than in the Sahara, and the values of ω0 are smaller than those in the Sahara. The regions with small ω0 values are consistent with the regions where coal-burning smoke and carbonaceous aerosols are thought to be transported, as reported in previous studies. Because the coal-burning and carbonaceous aerosols are known to be more absorptive and have smaller ω0 values than dust aerosols, our results indicate that the dust aerosols in Asia are contaminated by these anthropogenic aerosols. The spatial distribution of dust optical properties obtained in our work could be useful in understanding the roles of dust aerosols in the earth’s climate system, most likely through future collaboration with regional and global modelling studies.

• Title: New developments in ice sheet and glacier modeling
• Time: 14:45-16:15 on Oct 12, 2012.
• Place: General Research Bldg. 2F room 270.
• Abstract: Glaciers and ice sheets generally constitute shallow systems of coupled ice flow and thermal properties with complex boundary conditions at the free surface and the ice base. Numerical models of glaciers and ice sheets must solve a system of non-linear differential equations which is ill conditioned. The shallowness makes the response of vertical components of the flow very sensitive to perturbations in the horizontal components of the flow. The thermomechanical coupling through temperature dependent viscosity and advective heat transport, and the free surface increase the tendency to instabilities. To keep computational expenses reasonable, various approximations based on the shallowness of the ice mass have been applied. Recent developments attempt to introduce more elaborate schemes to include more physics, such as full Stokes flow, polythermal conditions, and its corresponding higher order equations, and more elaborate boundary conditions, such as sliding. In this talk, I present two examples of recent implementations of new schemes. A novel enthalpy scheme for polythermal ice sheets was implemented in the PISM ice sheet model and applied to Greenland. Full Stokes ice flow and a novel scheme for mass conservation and surface evolution in a glacier model have been applied to Alpine glaciers for various climatic scenarios.

• Title: Modeling study of the changes in summer precipitation characteristics over East Asia
• Time: 13:00-14:30 on Oct 12, 2012.
• Place: General Research Bldg. 2F room 270.
• Abstract: In this study, the East Asian summer monsoon (EASM) precipitation characteristic is investigated by using the high-resolution global downscaled dataset and uncoupled global circulation model (GCM) experiments with prescribed historical sea surface temperature (SST). From the global downscaled dataset, the tropics-related EASM precipitation is analyzed that can be divided into the TP and the IO related modes. In mid-1990s, these modes behave in opposite directions. TP mode increases rainfall of southern China and decreases precipitation over Korea-Japan regions. IO mode enhances rainfall over southern China and Korea-Japan regions. As combined effect of these two modes, the southern China area shows monotonic increase of rainfall, whereas Korea-Japan region shows compensated small variability. From uncoupled GCM experiments, it is shown that the IO and WP have opposite sensitivity of SST on EASM precipitation. IO and WP SST tend to increase and decrease EASM rainfall patterns, respectively. Effects of the local SST on the EASM are also investigated. The local SST warming increases the convective precipitation and does not have effects on the large-scale rainfall component. Consequently, the total amount of the precipitation and the CRR are increased by the local SST warming. It indicates that the local SST is important factor which can affect the changes of the EASM precipitation characteristics as much as the remote tropical ocean SSTs. The atmospheric internal forcing is defined as a difference between the global downscaled dataset and the uncoupled GCM experiment which is forced by historical SSTs. The precipitation variability of Northeast Asia shows relationship with the SST forcing and the atmospheric internal forcing. But, rainfall variability of the southern China region is mostly explained by the atmospheric internal forcing term.

• 場所: 総合研究棟　4センター共用2階会議室 270

• Title:火星大気大循環モデルを用いたダストストームの発生環境と時間発展に関する研究
• Time: 15:00-17:00 on Sep. 20, 2012.
• Place: General Research Bldg. 2F room 270.

• Title: 気象災害と損害保険
• Place: General Research Bldg. 2F room 270.
• Time: 13:30-15:00 on Jun 8, 2012.
• Abstract: 台風は日本に大きな被害をもたらす自然災害である。損害保険会社は企業向け・ 個人向けに、台風による損害をカバーする保険(火災保険など)を広く提供してい る。継続的な保険提供の為に、保険会社では過去の台風損害を精緻に分析するこ とで、持続可能な保険料(掛け金)を算出・利用している。 一方、IPCC・SREXでも指摘されているように、温暖化に伴う台風強度の増加が懸 念されている。この台風の将来変化は保険会社の経営に大きな影響を与える可能 性があるが、従来の手法(過去の統計解析)ではその影響を推定することは困難で ある。そこで、東京海上研究所では東京大学・名古屋大学と共同で、GCMの将来 予測結果を活用し温暖化後の台風リスクを推定する研究を行っている。本講演で は、自然災害が損害保険会社の経営に与える影響と、東京海上研究所が実施して いる温暖化台風リスク研究の取組み、そして昨年度から実施している気象庁・季 節予報データの解析結果について紹介する。

• Title: Ensemble-based Data Assimilation with the Weather Research and Forecasting (WRF) Model __Studies for Improving Tropical Cyclone Forecasts
• Time: 15:00-16:30 on Jun 5, 2012.
• Abstract: Data assimilation and predictability studies on Tropical Cyclones with a particular focus on intensity forecasts are performed with the newly-developed Local Ensemble Transform Kalman Filter (LETKF) system with the WRF model. Taking advantage of intensive observations of the internationally collaborated T-PARC (THORPEX Pacific Asian Regional Campaign) project, we focus on Typhoon Sinlaku (2008) which intensified rapidly before making landfall to Taiwan. This study includes a number of data assimilation experiments and sensitivity analysis which quantifies impacts of observations on forecasts. Recent achievements include higher-resolution data assimilation with two-way nested domains as well as improved forecasts due to including SST uncertainties in ensemble-based data assimilation.

• (1) 14:00-15:30 岡島秀樹（東京大学 大気海洋研究所）
  南極オゾン層回復が南大洋CO2吸収に及ぼす影響(Stratospheric ozone recovery and the scenario dependent Southern Ocean CO2 uptake)
  (2) 15:30-17:00 山崎邦子（東京大学 大気海洋研究所）
  Obtaining diverse behaviors in a climate model without the use of flux adjustments
• Place: General Research Bldg. 2F room 270.
• Time: 14:00-17:00 on May 25, 2012.
Abstract:
(1)To investigate the possible impact of stratospheric ozone depletion/recovery on the climate around the Antarctica, numerical experiments are carried out by using the state-of-the-art Earth System Model, with and without the atmospheric climate-chemistry feedback, under the various future warming scenarios. We will show preliminary results indicating the ozone depletion/recovery is more (less) effective under the moderate (drastic) warming scenarios. 温室効果ガス増加に伴う地表気温・海面温度の上昇は、全球で一様ではなく、Ice-Albedoフィードバックの働く極地方で顕著とされるが、ここ数十年の観測では、北極は大幅に昇温しているのに対して、南極はあまり昇温していない(IPCC 2007)。その理由として、南極オゾンホール発達に伴う極渦強化が、対流圏の極方向への熱輸送を妨げることが考えられるが(Thompson and Solomon 2002)、今後規制によりオゾン層が回復すると、極渦弱化に伴い南極も急激に昇温し、さらには南大洋のCO2吸収が加速されると懸念されている(Le Quere et al. 2007, Son et al. 2008, Lenton et al. 2009)。 炭素循環を含んだ地球システムモデルにCMIP5プロトコルに基づく温暖化シナリオを与えて実験したところ、RCP4.5シナリオ下ではオゾン層回復による極渦弱化の効果が顕れ、南極昇温および南大洋CO2吸収が加速された。一方、RCP8.5シナリオ下では温暖化による西風強化の効果が強く、オゾン層回復による極渦弱化は顕著ではない。一連の結果から、南極オゾンホール変化による周辺気候への影響は、温暖化シナリオに依存することが示唆された。
(2)Efforts have been made in past research to attain a wide range of atmosphere and ocean model behaviors by varying the parameters in model physics in perturbed physics ensembles (PPE). No PPE experiment, however, has been successful, to our knowledge, in obtaining a large spread of ocean model behavior compared to that exhibited in the ensemble of structurally different models (multi model ensemble), e.g. the CMIP3 ensemble. In this work we randomly vary model parameters of a coupled GCM within plausible ranges elicited from model developers in a space-filling latin-hypercube design containing 10,000 parameter combinations. The ensemble is run over the distributed computing platform of climateprediction.net under fixed pre-industrial forcing without flux adjustment. Furthermore, we resample a second, 20,000 member ensemble of perturbations conditioned on the diagnosed fluxes from the first ensemble to not drift significantly away from a realistic initial base state, a key step since we are not using flux adjustment. The conditioned ensemble is also run under the same fixed pre-industrial forcing as the first. The members of the conditioned ensemble attain the distribution of radiative fluxes very similar to those predicted. The radiatively balanced models within the conditioned ensemble show reasonably realistic regional control base climates in the atmosphere with deviations from observational data similar to those found in the CMIP3 ensemble, although there is a global mean bias. The range of predicted equilibrium climate sensitivities of the conditioned ensemble is substantially smaller than that obtained with flux adjustment (Stainforth et al. 2005), but still larger than the range in the CMIP3 ensemble (Solomon et al. 2007). The Atlantic Meridional Overturning Circulation (AMOC) exhibits a spread in strength as wide as that found in the CMIP3 ensemble. The conditioned ensemble is thus expected to have a wide range of change in the AMOC strength when it is run under enhanced CO2 conditions (Gregory et al. 2005). We conclude that flux adjustment is not a pre-requisite for obtaining a broad spread of behavior in a perturbed physics ensemble.

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