Shintaro Kawahara

The super‐droplet method for the numerical simulation of clouds and precipitation: a particle‐based and probabilistic microphysics model coupled with a non‐hydrostatic model

A novel, particle-based, probabilistic approach for the simulation of cloud microphysics is proposed, which is named the super-droplet method (SDM). This method enables the accurate simulation of cloud microphysics with a less demanding cost in computation. SDM is applied to a warm-cloud system, which incorporates sedimentation, condensation/evaporation and stochastic coalescence. The methodology to couple super-droplets and a non-hydrostatic model is also developed. It is confirmed that the result of our Monte Carlo scheme for the stochastic coalescence of super-droplets agrees fairly well with the solutions of the stochastic coalescence equation. The behaviour of the model is evaluated using a simple test problem, that of a shallow maritime cumulus formation initiated by a warm bubble. Possible extensions of SDM are briefly discussed. A theoretical analysis suggests that the computational cost of SDM becomes lower than the spectral (bin) method when the number of attributes—the variables that identify the state of each super-droplet—becomes larger than some critical value, which we estimate to be in the range . Copyright

A series of eddy-resolving ocean simulations in the world ocean - OFES (OGCM for the Earth Simulator) project

Ocean general circulation models (OGCMs) have long been used to investigate oceanic circulations and their variation with various spatial and temporal scales. Mesoscale eddies, which diameters are about 100 km, should be resolve in order to reproduce not only basin-scale circulation but also eddy activities and proper path of western boundary currents. They also play an important role to meridional transport of heat and momentum. Recently, an eddy-resolving OGCM simulation with 0.1/spl deg/ horizontal grid spacing in the North Atlantic basin suggests that OGCM should have the grid spacing of the order of 0.1/spl deg/ or finer. Although computational resource was not enough to execute global eddy-resolving simulation, the Earth Simulator (ES) with 40 Tflops peak performance, which currently is the fastest massive parallel computer for general purpose, changed the computational environment. The ES and OGCM highly tuned for the ES provide us the opportunities to execute several decadal integrations of the eddy-resolving OGCM simulation in the global domain. In This work, successful outcomes and advanced visualizations from a series of eddy-resolving simulations in the world ocean: a 50 year spin-up run, hindcast run from 1950 to 2003 and tracer run incorporated with chlorofluorocarbons (CFCs), are reported.

A Global Eddy-Resolving Coupled Physical-Biological Model: Physical Influences on a Marine Ecosystem in the North Pacific

Physical influences on a marine ecosystem in the open ocean are investigated using a simplified four-component ecosystem model embedded in an eddy-resolving ocean general-circulation model (OGCM). The annual cycle of temperature, nitrate, and phytoplankton in the upper ocean is well reproduced with the climatological monthly mean forcing.A comparison with satellite ocean color data shows that the model is capable of a realistic description of the annual mean and regional patterns of surface chlorophyll.Simulated chlorophyll distribution at the surface shows a pattern influenced by the western boundary current (Kuroshio) and meso-scale eddies.Nitrate distribution in the upper ocean in the northwestern Pacific is mainly controlled by physical processes, especially meso-scale variability, including many anticyclonic and cyclonic eddies, fine-scale fronts, and filaments.The warm-core eddy entrains high-nitrate water from the surrounding filaments, creating conditions for the high production in spring.

MovieMaker: a parallel movie-making software for large-scale simulations

We have developed a parallel rendering software for scientific visualization of large-scale, three-dimensional, time development simulations. The goal of this software, MovieMaker, is to generate a movie, or a series of visualization images from one terabyte-scale data set within one night (or less than 12 h). The isorontouring, volume rendering, and streamlines are implemented. MovieMaker is a parallel program for the shared memory architecture with dynamic load balancing and overlapped disk I/O.

Global 7-km mesh nonhydrostatic Model Intercomparison Project for improving TYphoon forecast (TYMIP-G7): Experimental design and preliminary results

Recent advances in high-performance computers facilitate operational numerical weather prediction by global hydrostatic atmospheric models with horizontal resolutions of ∼ 10 km. Given further advances in such computers and the fact that the hydrostatic balance approximation becomes invalid for spatial scales < 10 km, the development of global nonhydrostatic models with high accuracy is urgently required. The Global 7 km mesh nonhydrostatic Model Intercomparison Project for improving TYphoon forecast (TYMIPG7) is designed to understand and statistically quantify the advantages of high-resolution nonhydrostatic global atmospheric models to improve tropical cyclone (TC) prediction. A total of 137 sets of 5-day simulations using three next-generation nonhydrostatic global models with horizontal resolutions of 7 km and a conventional hydrostatic global model with a horizontal resolution of 20 km were run on the Earth Simulator. The three 7 km mesh nonhydrostatic models are the nonhydrostatic global spectral atmospheric Double Fourier Series Model (DFSM), the Multi-Scale Simulator for the Geoenvironment (MSSG) and the Nonhydrostatic ICosahedral Atmospheric Model (NICAM). The 20 km mesh hydrostatic model is the operational Global Spectral Model (GSM) of the Japan Meteorological Agency. Compared with the 20 km mesh GSM, the 7 km mesh models reduce systematic errors in the TC track, intensity and wind radii predictions. The benefits of the multi-model ensemble method were confirmed for the 7 km mesh nonhydrostatic global models. While the three 7 km mesh models reproduce the typical axisymmetric mean inner-core structure, including the primary and secondary circulations, the simulated TC structures and their intensities in each case are very different for each model. In addition, the simulated track is not consistently better than that of the 20 km mesh GSM. These results suggest that the development of more sophisticated initialization techniques and model physics is needed to further improve the TC prediction.

Realistic representation of clouds in Google Earth

We have developed a very simple method to represent cloud realistically with the aid of Google Earth. Two physical quantities computed in the atmospheric simulation model are utilized for the method. Figure 1 shows the display results of applying the proposed method. In this method, the downward shortwave radiation is used for determining the color of clouds and the cloud content for the opacity. These physical quantities are visualized separately by using the volume representation function of VDVGE and exported as content files for Google Earth. PNG images included in each content file are combined as new images with the color based on the downward shortwave radiation and the opacity based on the cloud content.

IMMERSIVE VR VISUALIZATIONS BY VFIVE PART 2: APPLICATIONS

VFIVE is a scientific visualization application for CAVE-type immersive virtual reality systems. The source codes are freely available. VFIVE is used as a research tool in various VR systems. It also lays the groundwork for developments of new visualization software for CAVEs. In this paper, we pick up five CAVE systems in four different institutions in Japan. Applications of VFIVE in each CAVE system are summarized. Special emphases will be placed on scientific and technical achievements made possible by VFIVE.

Real-time 3D visualization of phased array weather radar data via concurrent processing in Science Cloud

With the tremendous development of remote sensing technologies, a large amount of observation data are generated from sensors. Since each sensor generates data periodically, e.g., every minute, a concurrent data processing using a cloud system plays an important role in the modern design process. This paper focuses on concurrent data processing techniques for an X-band phased array weather radar (PAWR) using high-speed network, parallel data processing system, and large-scale storage system. The PAWR at National Institute of Information and Communications Technology (NICT), Japan rotates in 30 sec to capture a 3D structure of rainfalls within 60 km in radius and 15 km in altitude. In this paper, we develop a real-time 3D visualization system of the observation data of the PAWR. Our visualization is carried out from 54 sec to 69 sec (depending on the weather conditions) after every observation period, which is in the same time scale with other conventional 2D visualization of X-band weather radars. In addition, we discuss a combination of cloud ecosystems for the concurrent processing at low cost. The methodology is considered as a pioneering case study to develop of a variety of real-time data processing systems of big data via remote sensing.

Visualization for Eruption Cloud Simulations using MovieMaker

Volume rendering is one of the effective techniques for analysis of simulation results which have complex phenomena like as the volcanic smoke. We visualized the results of eruption cloud simulation using MovieMaker which is the high performance movie making software. Three dimensional structures of eruption cloud were become clear using volume rendering function of MovieMaker. In this work, we will report visualization results of large-scale eruption clouds simulation.

Current status of visualization advancing together with simulation researches on the Earth Simulator

Two kinds of visualization software, MovieMaker and VFIVE, developed at Earth Simulator Center are introduced. MovieMaker is a parallel rendering software for making sequential images from large scale simulation data. VFIVE is a virtual reality visualization software for interactive and immersive visualization in the CAVE system.