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Takahashi K.,Earth Simulator Center | Goto K.,NEC Corp | Fuchigami H.,NEC Informatec Systems LTD | Onishi R.,Earth Simulator Center | And 3 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

Multi-Scale Simulator for the Geoenvironment (MSSG), which is a coupled non-hydrostatic atmosphere-ocean-land model, has been developed in the Earth simulator Center. Outline of MSSG is introduced and its characteristics are presented. In MSSG, Yin-Yang grid system is adopted in order to relax Courant-Friedrichs-Lewy condition on the sphere. Furthermore, the Large-Eddy Simulation model for the turbulent atmospheric boundary layer and cloud micro physics model have been adapted for ultra high resolution simulations of weather/climate system. MSSG was optimized computationally on the Earth Simulator and its dynamical core processes had attained 51.5 Tflops on the Earth Simulator. Results from preliminary validations including forecasting experiments are presented. © 2011 Springer-Verlag Berlin Heidelberg.


Takahashi K.,Earth Simulator Center | Onishi R.,Earth Simulator Center | Sugimura T.,Earth Simulator Center | Baba Y.,Earth Simulator Center | And 2 more authors.
High Performance Computing on Vector Systems 2009 | Year: 2010

Multi-Scale Simulator for the Geoenvironment (MSSG), which is a coupled non-hydrostatic atmosphere-ocean-land model, has been developed in the Earth simulator Center. Outline of MSSG is introduced and characteristics are presented. After optimizing computational performance of MSSG, performance analysis has been performed on the Earth Simulator. As the results of optimization, ultra high performance with MSSG has been achieved. Computational performance of the coupled non-hydrostatic atmosphere-ocean-land model has attained 52-55% of theoretical peak performance. Furthermore, results from preliminary validations including forecasting experiments are presented. © Springer-Verlag Berlin Heidelberg 2010.


Takahashi K.,Earth Simulator Center | Onishi R.,Earth Simulator Center | Baba Y.,Earth Simulator Center | Kida S.,Earth Simulator Center | And 3 more authors.
Journal of Physics: Conference Series | Year: 2013

Mechanisms of interactions among different scale phenomena play important roles for forecasting of weather and climate. Multi-scale Simulator for the Geoenvironment (MSSG), which deals with multi-scale multi-physics phenomena, is a coupled non-hydrostatic atmosphere-ocean model designed to be run efficiently on the Earth Simulator. We present simulation results with the world-highest 1.9km horizontal resolution for the entire globe and regional heavy rain with 1km horizontal resolution and 5m horizontal/vertical resolution for urban area simulation. To gain high performance by exploiting the system capabilities, we propose novel performance evaluation metrics introduced in previous studies that incorporate the effects of the data caching mechanism between CPU and memory. With a useful code optimization guideline based on such metrics, we demonstrate that MSSG can achieve an excellent peak performance ratio of 32.2% on the Earth Simulator with the single-core performance found to be a key to a reduced time-to-solution.


Klein P.,French National Center for Scientific Research | Lapeyre G.,French National Center for Scientific Research | Roullet G.,French National Center for Scientific Research | Le Gentil S.,French National Center for Scientific Research | Sasaki H.,Earth Simulator Center
Geophysical and Astrophysical Fluid Dynamics | Year: 2011

High resolution simulations of ocean turbulence with Rossby number of order one have revealed that upper layer dynamics significantly differs from the interior dynamics. As reported before, upper layer dynamics is characterized with shallow velocity spectrum corresponding to kinetic energy distributed over a spectral range from mesoscales to small scales. This dynamics is driven by small-scale frontogenesis related to surface density anomalies. Interior dynamics is characterized by steeper velocity spectrum and is driven by the potential vorticity anomalies set up by the interior baroclinic instability. Impact of the divergent motions related to surface frontogenesis leads to a warming of the upper layers, a cyclone dominance and a negative skewness of the isopycnal displacements. On the contrary, divergent motions in the interior lead to a cooling of the deeper layers, an anticylone dominance and a positive skewness of the isopycnal displacements. These different ageostrophic processes are consistent with an SQG regime extended to Rossby number of order one on one hand and an interior QG regime extended to Rossby number of order one on the other hand, as proposed by previous studies. Synthesis of these characteristics suggest a connection between upper and deeper layers, induced by the divergent motions, through which small scales near the surface interact with mesoscales in the interior. © 2011 Taylor & Francis.


Ratnam J.V.,Research Institute for Global Change | Ratnam J.V.,Application Laboratory | Behera S.K.,Research Institute for Global Change | Behera S.K.,Application Laboratory | And 5 more authors.
Climate Dynamics | Year: 2012

The main aim of this paper is to evaluate the Advanced Research Weather Research and Forecasting (WRF) regional model in simulating the precipitation over southern Africa during austral summer. The model's ability to reproduce the southern African mean climate and its variability around this mean state was evaluated by using the two-tier approach of specifying sea surface temperature (SST) to WRF and by using the one-tier approach of coupling the WRF with a simple mixed-layer ocean model. The boundary conditions provided by the reanalysis-II data were used for the simulations. Model experiments were conducted for twelve austral summers from DJF1998-99 to DJF2009-10. The experiments using both the two-tier and one-tier approaches simulated the spatial and temporal distributions of the precipitation realistically. However, both experiments simulated negative biases over Mozambique. Furthermore, analysis of the wet and dry spells revealed that the one-tier approach is superior to the two-tier approach. Based on the analysis of the surface temperature and the zonal wind shear it is noted that the simple mixed-layer ocean model coupled to WRF can be effectively used in place of two-tier WRF to simulate the climate of southern Africa. This is an important result because specification of SST at higher temporal resolutions in the subtropics is the most difficult task in the two-tier approach for most regional prediction models. The one-tier approach with the simple mixed-layer model can effectively reduce the complicacy of finding good SST predictions. © 2011 Springer-Verlag.


Ratnam J.V.,Research Institute for Global Change | Ratnam J.V.,Application Laboratory | Behera S.K.,Research Institute for Global Change | Behera S.K.,Application Laboratory | And 6 more authors.
Climate Dynamics | Year: 2012

The winter months from December 2009 to February 2010 witnessed extreme conditions affecting lives of millions of people around the globe. During this winter, the El Niño Modoki in the tropical Pacific was a dominant climatic mode. In this study, exclusive impacts of the El Niño Modoki are evaluated with an Atmospheric General Circulation Model. Sensitivity experiments are conducted by selectively specifying anomalies of the observed sea surface temperature in the tropical Pacific. Observed data are also used in the diagnostics to trace the source of forced Rossby waves. Both the observational results and the model simulated results show that the heating associated with the El Niño Modoki in the central tropical Pacific accounted for most of the anomalous conditions observed over southern parts of North America, Europe and over most countries in the Southern Hemisphere viz. Uruguay. Unlike those, the model-simulated results suggest that the anomalously high precipitation observed over Australia and Florida might be associated with the narrow eastern Pacific heating observed during the season. © 2011 Springer-Verlag.


Lloyd-Hughes B.,University of Reading | Shaffrey L.C.,University of Reading | Vidale P.L.,University of Reading | Vidale P.L.,Earth Simulator Center | Arnell N.W.,University of Reading
International Journal of Climatology | Year: 2013

We compare the characteristics of synthetic European droughts generated by the HiGEM1 coupled climate model run with present day atmospheric composition with observed drought events extracted from the CRU TS3 data set. The results demonstrate consistency in both the rate of drought occurrence and the spatiotemporal structure of the events. Estimates of the probability density functions for event area, duration and severity are shown to be similar with confidence > 90%. Encouragingly, HiGEM is shown to replicate the extreme tails of the observed distributions and thus the most damaging European drought events. The soil moisture state is shown to play an important role in drought development. Once a large-scale drought has been initiated it is found to be 50% more likely to continue if the local soil moisture is below the 40th percentile. In response to increased concentrations of atmospheric CO2, the modelled droughts are found to increase in duration, area and severity. The drought response can be largely attributed to temperature driven changes in relative humidity. © 2012 Royal Meteorological Society.


Matsuoka D.,Earth Simulator Center | Araki F.,Earth Simulator Center | Kida S.,Earth Simulator Center | Sasaki H.,Earth Simulator Center | Taguchi B.,Earth Simulator Center
Proceedings - 2012 SC Companion: High Performance Computing, Networking Storage and Analysis, SCC 2012 | Year: 2012

Ocean currents and vortices play an important role in transferring heat, salt or carbon as well as atmospheric circulation. With advances in supercomputing technology, high-resolution large-scale simulation study has been focused in the field of ocean science. However, it is difficult to intuitively understand characteristic features defined as multivariable hiding in the high-resolution dataset. In order to obtain scientific knowledge from large-scale simulation data, it is important to effectively extract and to efficiently express the characteristic feature. The aim of this study is how to efficiently extract and how to effectively visualize ocean currents which affect the heat transportation. In this research, new multi-dimensional transfer function to emphasis the ocean currents and vortices is proposed. Furthermore, multivariate analyses to extract such features are developed. This presentation describes the methodologies and experimental results of these methods. Evaluation of visualization results and feedback to the parameter optimization will be also reported. © 2012 IEEE.


Taguchi B.,Earth Simulator Center | Qiu B.,University of Hawaii at Manoa | Nonaka M.,Kanagawa Institute of Technology | Sasaki H.,Earth Simulator Center | And 2 more authors.
Ocean Dynamics | Year: 2010

An eddy-resolving multidecadal ocean model hindcast simulation is analyzed to investigate timevarying signals of the two recirculation gyres present respectively to the north and south of the Kuroshio Extension (KE) jet. The northern recirculation gyre (NRG), which has been detected at middepth recently by profiling float and moored current meter observations, is a major focus of the present study. Lowfrequency variations in the intensity of the recirculation gyres are overall highly correlated with decadal variations of the KE jet induced by the basin-wide wind change. Modulation of the simulated mesoscale eddies and its relationship with the time-varying recirculation gyres are also evaluated. The simulated eddy kinetic energy in the upstream KE region is inversely correlated with the intensity of the NRG, consistent with previous observational studies. Eddy influence on the low-frequency modulation of the NRG intensity at middepth is further examined by a composite analysis of turbulent Sverdrup balance, assuming a potential vorticity balance between the mean advection and the convergent eddy fluxes during the different states of the recirculation gyre. The change in the NRG intensity is adequately explained by that inferred by the turbulent Sverdrup balance, suggesting that the eddy feedback triggers the low-frequency modulation of the NRG intensity at middepth. © Springer-Verlag 2010.

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