Effects
A reasonable simulation of the complex phenomena among the many
interacting processes of the climate change will lead us to comprehend the effects of
natural calamities, the long-term climate changes and other influence of human activities.
NJR Project
As our project to prepare the circumstance of climate change modeling on the
high performance computers, we have developed a platform of the NJR:Parallel Global
Climate Change Model with the high spatial resolution and the coupled multi-physics
models in flexible and transportable manners. The model is well parallelized through
both the domain decomposition and concurrent data-transfer, using message passing or
High Performance Fortran. Moreover, the model can be transported to various types of
highperformance computers and can be optimized for different machine architectures.
Climate System Model
The parallel atmospheric model was developed with referencing the
model, AGCM, originally developed at Center for Climate System Research of University of
Tokyo. The atmospheric model uses the spectral method with semi-implicit time integration.
The model consists of a dynamics module based on primitive equation, and column physics
modules consisting of parameterization of various processes for the simulation of the
atmosphere. The oceanic model was parallelized by referencing the Princeton Ocean Model,
POM and modified to allow a general parallel interface, "Coupler," between ocean and
atmosphere. The oceanic model adopts finite-difference method with the split explicit
time integration and the calculation is proceeded with the two paths, barotropic and
baroclinic mode. The baroclinic mode is calculated by using long time interval and the
barotropic mode is calculated by short time interval. The oceanic model is being extended
to include the sea ice model. The climate system model binds together atmospheric model,
oceanic model, sea ice model, and land surface processes. In future, atmospheric chemistry
model and ocean biogeochemistry model will be incorporated into the system. The
calculation is designed to assure the conservation of key physical quantities taking
account of the different mesh sizes and domains.
Parallelization
As for parallelism within the atmospheric model, the domain
decomposition is adopted for dividing the space along latitudes and processors are
deployed to the subdomains in user's manner. Each subdomain consists of a number of
columns having full vertical extent for the physical process. The data transfer is only
executed when the data are transposed through message passing MPI between FFT and Legendre
transformation. For the ocean model the space is also decomposed one-dimensionally and
dynamic and physical calculations are proceeded within subdomains. The data are passed
through the shadows between subdomains. Simple parallelism is our concept for model
development.
Simulations
Simulations using the atmospheric model (NJR-AGCM) and the ocean
model(NJR-OGCM) are being continued. The above figure shows the monthly mean (May)
precipitation amount(mm/day) and the 500 hPa streamlines simulated by the NJR-SAGCM
(T106L20,~120km horizontal resolution). The figure shows that much precipitations are well
simulated in the Intertropical Convergence Zone, the Southeast Asian Monsoon area. The
positions of major troughs and jet streams are also well simulated. The five-year
simulation by the NJR-OGCM (3Blat.x3Blon. resolution)is executed by specifying the
monthly mean (November) surface wind, sea surface temperature and salinity as the surface
boundary conditions. The figure below shows monthly mean sea surface elevation (m) and the
sea current (m/s) for the last simulated year. Large scale features are fairly well
simulated.
Future Efforts
Model verification is now being carried out development. Simulations
through scientific study of the ocean and atmosphere using the coupled model.
Optimization for the Earth Simulator is proceeded with focusing on partitioning and load
balancing. It suggests that the models have good performance in teraflops computing.
NJR: NASDA (National Space Development Agency of Japan), JAMSTEC
(Japan Marine Science & Technology Center), RIST (Research Organization for
Information Science & Technology).
For more information about NJR: Parallel Global Climate Change Models, contact
Research Organization for Information Science & Technology,
1-18-16 Sumitomo-hamamatsucho bldg.
10F, Hamamatsucho, Minato-ku, Tokyo
105-0013,
TEL: +81-3-3436-5271
FAX: +81-3-3436-5274