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アプリケーションラボ（APL）

セミナーのお知らせ

第38回 APL Open Forum

日時：
2017年12月22日（金） 15：45～17：15
場所：
交流棟2F 小会議室1+2
発表者1：
土井　威志
タイトル：
One hundred parallel worlds in seasonal prediction
概要
This study explores impacts of the ensemble size on the skill of seasonal climate prediction. We have evaluated differences in deterministic and probabilistic skill scores between two extremes (12 and 106) of ensemble outputs derived from a dynamical seasonal prediction system. A 100-ensemble retrospective seasonal forecast experiment has never been tried so far. One good news is that the prediction skill of El Niño/Southern Oscillation (ENSO) does not change significantly in the larger ensemble, indicating that the ensemble size of 10-members, used in most of the operational systems, is adequate for maintaining present level of ENSO prediction. Another good news is that some improvement is seen in the probabilistic prediction skills of extreme climate events in the extratropics. Even if running a 100-ensemble prediction system is quite costly, improved probabilistic prediction of disastrous extreme events may be useful for minimizing risks of possible human and economic losses.
発表者2：
山崎　哲
タイトル：
Using the Ensemble Forecast Sensitivity to Observations (EFSO) technique for global observing system experiments (OSEs)
概要
A global atmospheric data assimilation system called ALEDAS comprised of AFES (Atmospheric GCM) and LETKF (an ensemble Kalman Filter) has been developed, generated an experimental global ensemble reanalysis, and used to conduct several OSE studies to assess impacts of special observations obtained during some observational campaigns, especially on the Arctic and subtropical oceans. We have also performed some weather predictability studies by using the ensemble reanalysis and/or the OSE reanalyses as initial values for AFES. Recently, a diagnostic technique called Ensemble Forecast Sensitivity to Observations (EFSO) which can quantify how much each observation has improved or degraded the forecast without a data denial OSE experiment (in offline) has been implemented into ALEDAS. In my presentation, estimation by EFSO is compared with actual data denial experiments and whether the estimation can be helpful for our future global OSE studies is discussed.

第37回 APL Open Forum

日時：
2017年12月1日（金） 15：45～17：15
場所：
交流棟2F 小会議室1+2
発表者1：
野中　正見
タイトル：
Wind-driven and intrinsic interannual variability in the Kuroshio Extension jet and its eddy activities
概要
Given the possible importance of variability in the western boundary currents and associated eddy activities on oceanic physical states and ecosystem, it is important to understand dynamics of interannual to decadal variability in the western boundary currents. In the western boundary regions, it has been known that oceanic internal dynamics can induce interannual intrinsic variability under atmospheric forcing without interannual variability. In the present study, to investigate intrinsic interannual variability in the western boundary currents under realistic interannually varying forcing, we have conducted eddy-resolving quasi-global OGCM ensemble experiments for 35 years. Five ensemble members with slightly different initial conditions show substantial spread in their interannual variability under the identical atmospheric reanalysis fields. Even on interannual time scale, intrinsic variability (and thus uncertainty) is similar to or larger than the wind-driven variability in the western boundary current regions. Also, it is found that in the Kuroshio Extension region, part of interannual variability in eddy activity can be wind-driven and propagates westward associated with current speed anomalies. Further, potential predictability in eddy activity is shown to be increasing eastward along the Kuroshio Extension.
発表者2：
Ingo Richter
タイトル：
Contributions of internal atmospheric processes and remote forcing to equatorial Atlantic variability
概要
The tropical Atlantic is characterized by pronounced variability on interannual to decadal time scales that has been shown to affect rainfall over the Sahel region and South America, and to influence El-Niño-Southern Oscillation and global temperature trends. Thus prediction of tropical Atlantic variability is of great importance but current state-of-the-art dynamical prediction systems continue to be matched or even outperformed by persistence and statistical forecasts. This is particularly obvious in the equatorial Atlantic. The present study examines the role of internal atmospheric variability and remote forcing in equatorial Atlantic variability using the SINTEX-F GCM. In the control experiment, SST are strongly restored to observed SST for the period 1982-2014, while in the sensitivity experiments the SST are restored to observed annual climatology in three selected regions: the tropical Pacific, the tropical Atlantic, and the global oceans. Results suggest that a substantial portion of tropical Atlantic wind variability is due to internal atmospheric processes and therefore not predictable. The remaining surface wind variability, in both the equatorial and northern tropical Atlantic, appears to be remotely influenced. This suggests a diminished role for local coupled feedbacks like the Bjerknes feedback. On the other hand, it leaves open the possibility of more skillful tropical Atlantic prediction if remote SSTs and their influence on the Atlantic can be predicted more accurately.

APL ゲストセミナー

日時：
2017年11月17日（金） 15：30～17：00
場所：
横浜研究所 交流棟　2階　小会議室
発表者1：
Prof. Francois Engelbrecht (CSIR Natural Resources and the Environment, South Africa)
タイトル：
Climate change and habitability in southern Africa - insights from CSIR climate change projections
発表者2：
Dr. Johan Malherbe (CSIR Natural Resources and the Environment, South Africa)
タイトル：
The 2015/16 drought in the Kruger National Park in the context of ENSO, decadal variability and anthropogenic climate forcing
発表者3：
Dr. Asmerom Beraki (CSIR Natural Resources and the Environment, South Africa)
タイトル：
The role of SH Mid-latitude and polar climate dynamics on Southern Africa climate variability from Earth System Model

第36回 APL Open Forum

日時：
2017年10月27日（金） 15:45～17:15
場所：
交流棟2F 小会議室1+2
発表者1：
Eda Chang
タイトル：
Potential impact of ocean circulation on the declining Japanese eel catch
概要：
The potential impact of ocean circulation on the declining Japanese eel catch in the Western North Pacific is examined based on a three-dimensional particle-tracking method, in which v-larvae are programmed to swim horizontally and vertically, in addition to movements carried passively by ocean currents. Observed Japanese eel catch is descending year by year. Human activities are considered to be one of the leading factors responsible for the decrease in eel catch. In our simulation, virtue larvae (v-larvae) dispersion towards North East Asia descends in recent two decades, indicating ocean circulation also plays an important role influencing the eel larvae migration. In recent years, instead of entering Kuroshio and moving towards North East Asia as in the 1990s’, v-larvae tend to migrate southward due to the weakening of westward NEC and strengthening of subsurface southward flow near spawning ground. The changing of ocean circulation in western Pacific is caused by the weakening of subtropical and tropical wind stress curl in past two decades. Under the changing climate, change of atmospheric condition influences the ocean circulation, then further impact on the Japanese eel larvae migration.
発表者2：
石津　美穂
タイトル：
Ocean acidification trends in coastal waters in Japan
概要：
Long-term pH trends in coastal waters in Japan were examined by using water quality measurements in public waters from 1978 to 2009 at 1258 monitoring sites, archived by Regional Development Bureau of Ministry of Land, Infrastructure, Transport and Tourism under Ministry of the Environment, in the monitoring program following the Water Pollution Control Law. Long-term pH trends averaged at the whole of monitoring sites showed the tendency to acidify; 72% and 28% of the monitoring sites showed the trends to acidify and alkaline, respectively. The average of pH trends was -0.0015 yr-1, which is comparable to that in the open ocean. Distinct trends to acidify with statistically significance were detected at 96% of monitoring sites. No latitudinal and longitudinal patterns of the trends were found, but our data indicated the general tendency in coastal waters in Japan that ocean acidification has certainly progressed even if coastal waters are influenced by multiple processes of coastal biogeochemistry as well as the impact of uptake of anthropogenic CO2.

第35回 APL Open Forum

日時：
2017年9月29日（金） 15:45～17:15
場所：
交流棟2F 小会議室1+2
発表者1：
古惠　亮
タイトル：
Coastal currents along the west and south coasts of Autralia
概要：
A recent analysis of the volume budget of the surface coastal current (the Leeuwin Current) along the west coast of Australia revealed a large downwelling from the surface current. As an extension to this work, I’ll show two recent results. First I’ll show a result of a similar analysis of the coastal current system along the south coast of Australia and then a preliminary analysis of the diapycnic/isopycnic fluxes in the Leeuwin Current in an eddy-resolving model, OFES.
発表者2：
日原　勉
タイトル：
Ocean data assimilation experiments using high resolution satellite sea surface temperature around Japan
概要：
The Japan Aerospace Exploration Agency (JAXA) operates the several earth observation satellites, and provides satellite sea surface temperature (SST) data. Satellite capability to detect SST fields is advancing in recent years. However, satellite SST data include some missing depending on the type of satellites and sensors, and don’t provide information on vertical oceanic conditions. This study aims at constructing a temporally and spatially uniform ocean dataset, using a data assimilation method which combines the satellite SST and the ocean model data. Our target area is south of Japan where the Kuroshio flows. The data assimilation technique and ocean model used for the present study are the Local Ensemble Transform Kalman Filter (LETKF) and the Stony Brook Parallel Ocean Model (sbPOM), respectively. We assimilate the observation data including four satellite SST products: Himawari-8/AHI and GCOM-W/AMSR2 provided by JAXA and Terra, Aqua/MODIS provided by National Aeronautics and Space Administration. It is important to apply the bias correction to the observation data prior to data assimilation in order to obtain better assimilation results. To check biases, we compared the satellite SST data with in situ SST data obtained around Japan (120-150˚E, 25-40˚N) for one year period (from May 2016 to April 2017). Analysis showed that the difference between Himawari/AHI SST and in situ SST clearly changed seasonally (maximum: 0.6˚C in September, minimum: -0.2˚C in February), which was not seen in the other satellite SST products. We validated results of several assimilation experiments focusing on effects of the satellite SST data assimilation. Validation using data of buoys moored off a south coast of Japan showed that accuracy of the analysis data improved when we corrected the bias of the satellite SST. Furthermore, it was found that impacts of the satellite SST assimilation on the analysis data profoundly depend on characteristics of the satellite SST products.

APL ゲストセミナー

日時：
2017年9月22日（金） 14:00～15:30
場所：
横浜研究所 交流棟　2階　小会議室
発表者：
Dr. Adrian Tompkins (ICTP, Italy)
タイトル：
Automated forecast calibration; convective organization in radiative convective equilibrium; and malaria early warning systems
概要：
Part 1: A Monte Carlo Markov Chain constrained genetic algorithm technique is presented to automate the calibration of numerical models. I will show some preliminary results using the classic Lorenz system for a 3 parameter system and a disease model for a 22 parameter system and discuss issues with deterministic prediction versus climate calibration.

Part 2: Convective organization has the potential to be a strong negative feedback on climate, but the mechanisms for organization are still poorly understood. We show how updraft entrainment is a critical (and often overlooked) process in the organization of convection, irrespective of the role of diabatic processes. A theory is presented for determining whether organization will occur or not (testing of the theory is currently underway).

Part 3: Malaria is an impact of climate. A new numerical model for malaria is briefly presented, along with some examples of its use in research in both the early warning and climate change context.

第34回 APL Open Forum

日時：
2017年8月25日（金） 15:45～17:15
場所：
交流棟2F 小会議室1+2
発表者1：
池田　隆美
タイトル：
Predicting Malaria Outbreak in Limpopo using Machine Learning Methods
概要：
Global malaria cases have drastically dropped in recent years, however there is still high incidence in sub-Saharan African countries. South Africa is mostly malaria-free, but northeastern provinces, such as Limpopo, still have seasonal transmission of malaria. Past studies have reported various relationships between malaria and local climatic factors as well as those in neighbouring countries (like Mozambique). The aim of this study is to use machine learning methods to predict malaria outbreak in Limpopo province at a district level. Monthly malaria counts for each district were dichotomized as "outbreak" or "not outbreak" based on median count values as a threshold for each season. Gridded climate data for the study period were extracted from NCEP/DOE Reanalysis II, CMAP, and NOAA, and were used for the learning process through repeated cross-validation. Algorithms ranged from logistic regression to more complex classification methods such as support vector machines, neural networks, and tree models. Bagged and boosted methods were also used, as well as a kappa-weighted ensemble model. All models were thoroughly trained, tested and validated. Models were then compared to obtain the best performing model based on performance measures (e.g. Cohen's kappa statistic). The best model was used to predict whether an outbreak would occur for upcoming malaria seasons. With up to three months of lead time, the predictions can provide an early warning for malaria in Limpopo by supplying adequate time for medical response units to prepare for the outbreak, and as a result, minimize its impact.
発表者2：
J. Venkata Ratnam
タイトル：
Improving SINTEX-F2 forecasts over southern Africa by bias correcting the leading modes of variability
概要：
Analysis of the SINTEX-F2 austral summer forecasts indicates the model to have limited skill in forecasting precipitation over the southern Africa landmass. We tried to improve the precipitation forecasts by bias correcting the leading modes of variability. The bias correction technique is found to be beneficial in improving the October and November initialized austral summer precipitation anomaly forecasts of SINTEX-F2 over the southern Africa landmass.

第33回 APL Open Forum

日時：
2017年7月28日（金） 15:45～17:15
場所：
交流棟2F 小会議室1+2
発表者1：
山本　絢子
タイトル：
The absence of an Atlantic imprint on the multidecadal variability of wintertime European temperature
概要：
Atlantic Multidecadal Oscillation (AMO) is a low frequency fluctuation in sea surface temperature (SST) over the North Atlantic basin with a period of 50 - 80 years, and studies show that Northern Hemisphere climate responds sensitively to this multidecadal variability. It is therefore surprising that an imprint of such variability is conspicuously absent in wintertime western European temperature, despite that Europe’s climate is strongly influenced by its neighbouring ocean, where multidecadal variability in basin-average SST persists in all seasons. In this study, we investigate this missing AMO imprint by using a novel Lagrangian methodology driven by National Centers for Environmental Prediction/National Center for Atmospheric Research 20th-Century Reanalysis. Our result suggests that this missing imprint is attributed to a dynamic anomaly of the atmospheric circulation associated with the difference in the underlying AMO phase, which suppresses the expected fluctuations in air-sea heat flux accumulated along the trajectories travelling to western Europe. Given that AMO is at least partly driven by the Atlantic Meridional Overturning Circulation (AMOC), which is projected to decline under global warming, our result provides an important implication, such that this atmospheric dynamical adjustment to the AMO may provide a possible stabilizing feedback for the slowdown of the AMOC. In this presentation, I will also briefly present the preliminary results of my ongoing project.
発表者2：
小守　信正
タイトル：
Experimental seasonal climate prediction using CFES: Preliminary results
概要：
An experimental seasonal climate prediction system has been developed based on the Coupled atmosphere-ocean general circulation model for the Earth Simulator (CFES). Following the well-established system based on the SINTEX-F model, initial conditions for seasonal climate prediction are constructed by strongly nudging sea surface temperature (SST) to observed one.
The atmospheric component of CFES has the resolution of T119 in the horizontal and 48 sigma-layers in the vertical with the top level placed at about 3 hPa. The oceanic component has a resolution of 1/2 degree in the directions of both longitude and latitude and 54 levels in the vertical. They are coupled every hour.
At this stage, 3-member ensemble 6-month predictions from the 1st day of March, June, September, and December have been conducted from 1983 through 2016, after 32-years of coupled spin-up integration with SST-nudging to the observed climatology. The experimental system exhibits skill in predicting SST variability in the tropical Pacific.

APL ゲストセミナー

日時：
2017年7月13日（木） 14:00～15:00
場所：
横浜研究所 交流棟　2階　小会議室
発表者：
Dr. Chaoxia Yuan (University of Information Science & Technology, Nanjing, China)
タイトル：
Interannual and decadal variations of winter extreme cold days in North China
概要：
-

第32回 APL Open Forumとゲストセミナー

日時：
2017年6月30日（金） 15:15～17:00
場所：
交流棟2F 小会議室1+2
発表者1：
（ゲストスピーカー）：Prof. Kelvin Richards (Director, IPRC)
タイトル：
Viral attacks on plankton blooms
概要：
Viruses attack marine organisms from bacteria to whales. In particular phytoplankton blooms can crash because of viral infection. Here we will explore the interaction between viruses, phytoplankton and zooplankton under bloom conditions using relatively simple models. One aspect under consideration is how viruses and zooplankton can co-exist. We should not forget that interactions take place in a fluid environment. Stirring and mixing is found to have a profound effect on viral epidemics and under certain circumstances can totally suppress the bloom.
発表者2：
馬場　雄也
タイトル：
Response of rainfall to land surface properties under weak wind shear conditions
概要：
Responses of rainfall trends to land surface properties (roughness length and sensible heat flux) under weak wind shear conditions were investigated by numerical simulation and idealized experiments. The results show that total amount, spatial pattern and intensity of rainfall were highly affected by the difference in sensible heat flux rather than the difference in roughness length. The initiation time for occurrence of rainfall became more delayed and the rainfall intensified as the given sensible heat flux decreased. A smaller sensible heat flux and a larger roughness length increased the convective available potential energy before the rainfall occurrence, resulting in stronger initial convection. The initiation processes affected the resulting convective structure, such that initial latent heat release occurred and remained downstream, leading to a widely spread convective structure above the cold pool. Spread and connected convection magnified the upright structure, thereby causing release of much more latent heat for ice water species and thus stronger rainfall intensity.
In addition to the first topic, I would like to show some recent results from analysis on intraseasonal variability simulated by cloud-resolving model based cumulus parameterization.

APL ゲストセミナー

日時：
2017年6月1日（木） 13:30～14:30
場所：
横浜研究所 交流棟　2階　小会議室
発表者：
Dr. Caradee Wright (Specialist Scientist, Environment and Health Research Unit, South African Medical Research Council, Pretoria, South Africa)
タイトル：
Projects in Environment, Climate and Public Health at the South African Medical Research Council and our role in SATREPS iDEWS
概要：
The Medical Research Council (MRC) in South Africa was established in 1969 with the aim to promote the improvement of the health and the quality of life of South Africans through research, development and technology transfer. The Environment and Health Research Unit (EHRU) of the MRC aims to conduct population-based research on environmental risks to human health with special emphasis on those living in poverty. A team of fourteen people work in four programmes: urbanization and urban health; lead poisoning prevention; exposure to environmental pollution and associated risks; and climate change and public health. The SATREP iDEWS project is a key climate-health project in which the EHRU has two tasks. The first is to collect hospital admissions data on infectious diseases diarrhoea and pneumonia for analysis and towards a prediction model to give early warnings to the healthcare sector to improve preparedness. The second is to determine environmental risk factors at household level for diarrhoea and pneumonia, and to estimate prevalence of these two diseases from a community-based household survey. To date, hospital records totalling 44,159 cases for all admissions have been captured for 2002 to 2016 and will now be analysed for diarrhoea and pneumonia in relation to temperature, rainfall and other climate variables. Four field campaigns have been conducted. Data on indoor household temperature, air quality, water and soil quality, socio-demographics, biomedical information, disease and lifestyle data have been collected from 400 households - 100 homes in each of 4 villages in Limpopo Province in the northeast of the country. Preliminary analysis of environmental samples (n=192) suggest that a concerning 94% of all drinking water samples contained coliform bacteria and 49% of samples contained E.coli. Mean indoor household temperature during spring/summer months was 28 °C with maximums in excess of 40 °C. With a wealth of data now available, the SATREPS iDEWS team in Japan and South Africa will commence several collaborative analyses towards the development of the early warning system for diarrhoea and pneumonia prevention.

APL ゲストセミナー

日時：
2017年5月26日（金） 15:00～16:00
場所：
横浜研究所 交流棟　2階　小会議室
発表者：
Prof. Lakshmi Kantha (University of Colorado at Boulder, USA)
タイトル：
Turbulent Mixing in the Oceans and the Atmosphere - Similarities and Differences
概要：
During my professional career, I have had the privilege of studying turbulence and mixing in both the oceans and the atmosphere. This has provided a unique insight into turbulent processes, specifically the similarities and differences between the two media. Unlike the atmosphere, except for a thin upper layer, oceans are opaque to electromagnetic signals and hence it is difficult to visualize turbulent processes in the interior. Only low frequency acoustic waves can be used to probe the interior of the global oceans. On the other hand, radars, sodars and lidars can all be used in the atmosphere. Special radars, such as the MU radar at Shigaraki, Japan, can be used to infer turbulence in the troposphere. During our ShUREX (Shigaraki UAV-Radar Experiment) campaigns in 2015 and 2016, we also discovered that it is possible to visualize layered and turbulent structures in the moist troposphere in unprecedented detail, when the radar is operated in range-imaging mode. The MU radar enabled us to probe interesting turbulent structures in real time using UAVs equipped with turbulence sensors and guided by high resolution radar echoes. I will present some of our findings that highlight some remarkable similarity to oceanic structures.

I will also present some preliminary results from my attempts to update the widely popular Kantha and Clayson (2004) second moment closure model of the upper oceanic mixed layer. This involves incorporating the Craik-Leibovich vortex force terms in second moment equations and doing a better job of modeling free convection. I will also discuss the difficulties involved in dealing with conventional and double-diffusive mixing that can occur together in some regions of the global oceans.

APL ゲストセミナー

日時：
2017年5月24日（水） 13:30～14:30
場所：
横浜研究所 交流棟　2階　小会議室
発表者：
Prof. Rhodora V. Azanza (University of the Philippines)
タイトル：
Researches and other Activities of the University of the Philippines' Marine Science Institute (UP-MSI)
概要：
The country's National Center for Marine Science is the University of the Philippines Marine Science Institute. It is a recognized center of excellence for the advancement, dissemination and application of knowledge in the marine science. Engaged in basic and applied research towards the advancement of tropical marine science, it also provides graduate level training and capacity building in various fields of marine science. Over 10 years strategic integrated Research Education Extension and Development Programs included: 1.) Marine biological Diversity and Tropical Ecosystem: Integrating Science and Management, 2.) Climate Change and Archipelagic Development Adaptive Management, 3.) Marine Biotechnology: Frontier Science and Advanced Applications, and 4.) Archipelagic Oceanography: Integrating Biological, Physical, Chemical and Geological Oceanography.

In the ranks of the MSI faculty are National Scientists, Academicians and Corresponding Members of the National Academy of Science and Technology, and other national and international awardees.

第31回 APL Open Forum

日時：
2017年5月19日（金） 13:45～15:30
場所：
交流棟2F 小会議室1+2
発表者1：
森岡　優志
タイトル：
Decadal climate predictability in the southern Indian Ocean using SINTEX-F2 coupled GCM
概要：
Decadal climate variation in the southern Indian Ocean plays a crucial role in rainfall variability over southern Africa through changes in moisture transport. The rainfall increase over southern Africa has a strong relation with warm sea surface temperature (SST) and high sea level pressure (SLP) anomalies in the Southwest Indian Ocean. Despite many efforts devoted to understanding the physical mechanisms, few studies have examined the decadal climate predictability in the southern Indian Ocean. This study aims at investigating decadal climate predictability in the southern Indian Ocean using a state-of-the-art coupled general circulation model (GCM), called SINTEX-F2. Here we performed 12 ensemble decadal hindcast experiments using different initial conditions with SST-nudging scheme, starting from Mar 1st in each year of 1982-2006.
On decadal timescale, the observed SST anomalies averaged in the Southwest Indian Ocean show positive peak in late 1990s and negative peak in late 2000s. Both positive and negative peaks are well reproduced in the decadal hindcast runs initiated in 1994 and 1999, respectively. Particularly, the decadal hindcast experiments initiated from 1999 successfully capture a distinct phase change from the positive to negative peak. In addition, the spatial patterns of warm SST and high SLP anomalies observed in late 1990s show a clear eastward propagation from the South Atlantic to the southern Indian Ocean along the Antarctic Circumpolar Current. The decadal hindcast experiments initiated in 1994 successfully capture this observed eastward propagation of SST and SLP anomalies from the South Atlantic, indicating an important role of SST anomalies in the South Atlantic. These results suggest that the SINTEX-F2 decadal hindcast experiments, with simple SST-nudging initialization, have reasonable skill in predicting the decadal climate variability of the southern Indian Ocean, important for the southern African climate.
発表者2：
尾形　友道
タイトル：
Effect of Air-Sea coupling on the Frequency Distribution of Intense Tropical Cyclones over the Northwestern Pacific (my past research)
概要：
Climate prediction with the recent supercomputer enables tropical cyclone (TC) simulation with 20km-AGCM (Murakami et al. 2012), and TCs in MRI-AGCM has become more realistic intensity by updated convection scheme. However, extreme TC in 20km-AGCM (category 5：>70m/s) still have northward bias (too little at 10-20N, too much at 20-30N). As possible causes of such bias, one is insufficient atmospheric modeling (Kanada et al. 2013) and the other is lack of air-sea coupling process.
In order to improve the northward TC bias, we developed AOGCM (oceanic component of MRI.COM was coupled to 60km MRI-AGCM3.2) and investigated air-sea coupling effect. In addition, I would like to talk about future research plan at APL.

第30回 APL Open Forum

日時：
2017年4月21日（金） 15:45～17:30
場所：
交流棟2F 小会議室1+2
発表者1：
Kunihiro Aoki
タイトル：
The Reynolds stress derived from axisymmetric eddies
概要：
Mesoscale eddies generated by instability of an oceanic jet causes a horizontal Reynolds stress, which influences temporal evolution of the jet. The Reynolds stress has often been explained in connection with a horizontal shape of an eddy, but the eddies widely populated in the ocean have nearly axisymmetric shape. This study analytically examines a fundamental property of the horizontal Reynolds stress caused by axisymmetric mesoscale eddies that occur with a realistic horizontal distribution of occurrence probability. The axisymmetric eddies are shown to have meridionally divergent and convergent Reynolds stresses in an upstream and a downstream region of the jet, respectively. This horizontal pattern is consistent with the stabilization and destabilization of the jet due to the eddy-mean flow interaction shown in previous numerical experiments. Our Reynolds stress, however, yields dynamic pressure, which has no contribution to dynamics of incompressible fluid such as quasi-geostrophy, but yields ageostrophic circulation over the jet’s region. This suggests that occurrence of the axisymmetric eddies obscures the Reynolds stress that is meaningful for the dynamics in the real ocean. To eliminate contamination by the axisymmetric eddy in the Reynolds stress, we propose a shape-dependent calculus of the Reynolds stress, which may be applicable to studies on parameterization of eddy influences.
発表者2：
Marie-Fanny Racault
タイトル：
Impact of El Niño Variability on Oceanic Phytoplankton
概要：
Oceanic phytoplankton respond rapidly to a complex spectrum of climate-driven perturbations, confounding attempts to isolate the principal causes of observed changes. A dominant mode of variability in the Earth-climate system is that generated by the El Niño phenomenon. Recently, marked variations have been observed in the centroid of anomalous warming in the Equatorial Pacific under El Niño, associated with quite different alterations in environmental and biological properties. Here, using observational and reanalysis datasets, we differentiate the regional physical forcing mechanisms and associated biological impacts caused by two extreme types of El Niño. The regional effects, greatest in the Equatorial Pacific but felt everywhere, can be considerable, and even of opposing signs during Eastern and Central Pacific types of El Niño. Analysis of the dominant mechanisms forcing the biophysical interactions under El Niño variability may provide a useful guide to improve our understanding of projected changes in the marine ecosystem in a warming climate and support development of adaptation and mitigation plans.

APL ゲストセミナー

日時：
2017年4月19日（水） 14:30～15:30
場所：
横浜研究所 交流棟　2階　小会議室
発表者：
Dr. Eric Maisonnave (CERFACS, Toulouse, France)
タイトル：
Measurements of real computational performance of ESMs
概要：
A climate model represents a multitude of processes on a variety of time and space scales; a canonical example of multi-physics multi-scale modeling. The underlying climate system is physically characterized by sensitive dependence on initial conditions, and natural stochastic variability, so very long integrations are needed to extract signals of climate change. Algorithms generally possess weak scaling and can be I/O and/or memory bound. Such weak-scaling, I/O and memory-bound multi-physics codes present particular challenges to computational performance.
Traditional metrics of computational efficiency such as performance counters and scaling curves do not tell us enough about real sustained performance from climate models on different machines. They also do not provide a satisfactory basis for comparative information across models. We introduce a set of metrics that can be used for the study of computational performance of climate (and Earth System) models. These measures do not require specialized software or specific hardware counters, and should be accessible to anyone. They are independent of platform, and underlying parallel programming models. We show how these metrics can be used to measure actually attained performance of Earth system models on different machines, and identify the most fruitful areas of research and development for performance engineering.
We present results for these measures for a diverse suite of models from several modeling centres, and propose to use these measures as a basis for a CPMIP, a computational performance MIP.

APL ゲストセミナー

日時：
2017年3月27日（月） 14:30～15:30
場所：
横浜研究所 交流棟2F　小会議室
発表者：
Dr. Yvan Orsolini (Senior Scientist, Norwegian Institute for Air Research)
タイトル：
Impact of Springtime Snow Over the Himalaya-Tibetan Plateau on the Onset of the Indian Summer Monsoon
概要：
-

APL ゲストセミナー

日時：
2017年3月24日（金） 14:00～16:00
場所：
横浜研究所 交流棟　2階　小会議室
発表者1：
Dr. Netrananda Sahu (Delhi School of Economics)
タイトル：
Impact of ENSO on Rice Yield in Bihar
概要：
-
発表者2：
Dr. H. Annamalai (University of Hawaii)
タイトル：
Extended monsoon episodes over South Asia: Assessing thermodynamic processes in reanalysis ensemble
概要：
During the season (June through September), rainfall associated with the South Asian summer monsoon fluctuates between active (enhanced convection) and break (subdued convection) spells, strengthening and weakening the seasonal-mean monsoon, respectively. Over the Indian subcontinent, the occurrences of extended (events lasting seven days or more) break and active conditions (hereafter referred to as “extended monsoon episodes”) during the peak monsoon phase (July-August) often leads to seasonal-mean droughts and floods, respectively. A question of interest here is: What are the leading dynamical and thermodynamical processes responsible for the break and active conditions to persist for an extended period? Recognizing that monsoon region is data void, particularly in three-dimensional thermodynamical variables, a careful assessment of the processes in a suite of reanalysis products appears reasonable. By applying vertically integrated moist static energy budget analysis, we seek “robustness” in the identified processes across reanalysis ensemble. The over-all hope is that such a process-based diagnostic would lead to objectively validate dynamical models that are being employed for extended-range prediction of monsoon rainfall.

第29回 APL Open Forum

日時：
2017年2月24日（金） 16:00〜17:45
場所：
横浜研究所 情報技術棟4F 会議室403+404
発表者1：
Hideharu Sasaki
タイトル：
Preliminary results from OFES2 at horizontal resolution of 1/10° and 1/30°
概要：
The OFES data from a near-global 1/10° ocean simulation have been widely used to many researchers, and many papers using the data have been published. However, there are some issues in the OFES: no sea-ice model, no tidal mixing, unrealistic Kuroshio path and so on. In order to try improving these issues, I conducted a new 1/10° near-global OFES hindcast simulation (named by OFES2) with a tidal mixing parameterization, sea-ice model, and SST and SSS restoring in marginal seas. The preliminary results from the OFES2 show some improvements, e. g. realistic vertical distribution of salinity in the Indonesian Archipelago region and Arabian Sea. Following the 1/10° OFES2, I conducted 2 year hindcast simulation of the 1/30° OFES2 from 2000 to 2001. The quick look shows rich winter submesoscales in both hemispheres.
発表者2：
Ingo Richter
タイトル：
The influence of tropical Pacific SST variability on local winds and the North Pacific
概要：
The influence of tropical Pacific SST variability on surface winds in the tropics and extra-tropics is investigated by using a set of sensitivity experiments with the SINTEX-F2 coupled model. In the 300-year control simulation (CTL) the model evolves freely. In the 300-year sensitivity test (TP), on the other hand, SSTs in the tropical Pacific (20S-20N) are restored to the monthly climatology of CTL.
Despite the absence of SST anomalies in TP, the experiment displays significant surface wind variability over the tropical Pacific, with variance over the Nino 4 region about 40% of that in CTL. Further to the east the residual variability is even more pronounced, with TP’s values in the far eastern tropical Pacific actually exceeding CTL.
Over the North Pacific, sea-level pressure variability substantially reduces in TP. This reduction is particularly pronounced over the northeastern Pacific, while there is some increase of variability in the western North Pacific around Japan. A spectral analysis of the Pacific Decadal Oscillation (PDO) index indicates that the most substantial drop in variability happens at decadal and longer time scales.
Potential mechanisms will be discussed.

第28回 APL Open Forum

日時：
2017年2月3日（金） 15:45～17:30
場所：
横浜研究所 交流棟2F 小会議室1+2
発表者1：
Masami Nonaka
タイトル：
Seasonality in sea surface salinity and relating sea surface variables
概要：
With accumulation of salinity observational data by Argo floats, it becomes possible to investigate salinity variability on seasonal to interannual time scales. While we know that there is strong seasonality in sea surface temperature (SST), seasonality in sea surface salinity (SSS) is not known well. Based on gridded Argo and other observational data and atmospheric reanalysis data, we examine global distribution of SSS seasonality using 12-month lagged auto-correlation map. In contrast to SST, which shows clear seasonality except for the tropical oceans especially in the Pacific, seasonality of SSS is not clear in large part of the global ocean except for tropics in the eastern Atlantic, the eastern Pacific, and the western Indian Oceans. Meanwhile the distribution depends on data products to some extent. Consistent with the limited seasonality, forcing field for SSS, i.e., precipitation-evaporation, Ekman transport, and geostrophic current advection also show limited seasonality except for the tropical oceans.
発表者2：
Akira Yamazaki
タイトル：
Introduction and recent development of the AFES-LETKF data assimilation system
概要：
We have developed our global data assimilation system called ALEDAS composed of the atmospheric GCM for the Earth Simulator (AFES) and the local ensemble transformed Kalman filter (LETKF). ALEDAS has been generated an experimental ensemble global reanalysis ALERA2 (AFES-LETKF experimental ensemble reanalysis version 2).The ALERA2 dataset has been archived for the period from 2008 to near real time (September 2016 at present) and part of the dataset (2008–2012) is available in the website. Using ALEDAS we have conducted the observing system experiments (OSE) to estimate the impacts of specific observations (especially radiosonde) taken at a region in the globe on reproducibility of various atmospheric phenomena in synoptic to large scales. In the recent studies I have focused on the impacts on predictability of some atmospheric disturbances in extratropical latitudes and propagation processes of the signals or errors by assimilating these observations. In the presentation I will introduce about ALEDAS and the recent OSE studies. In addition, a diagnostic technique, Ensemble Forecast Sensitivity to Observations (EFSO) has been implemented into ALEDAS. The EFSO can quantify how much each observation has improved or degraded the forecast without data denial experiments. Preliminary results using the EFSO also will be introduced in the presentation.

APL ゲストセミナー

日時：
2017年1月18日（水） 14:00～15:00
場所：
横浜研究所 情報技術棟　4階　会議室 403+404
発表者：
Dr. Neville Sweijd (Acting Director, ACCESS, South Africa)
タイトル：
Update on the dynamics of climate variability and diarrhoea and pneumonia incidence in Limpopo Province