Marine Ecosystems Research Department - jamstec japan agency ...

Japan Marine Science and Technology Center
Frontier Research System for Global Change
realistically. On the other hand, the model should run
efficiently on the Earth Simulator. We have set a target
that a -model-year integration should be done in
one calendar month. We have successfully achieved
these targets through the following activities.
a. Development of a Coupler for Rotated Ocean
Since the horizontal coordinate of the ocean model
is longitude-latitude grid, a singularity occurs at the
North Pole, around which longitudinal grids are concentrated.
To avoid this problem, the ocean model
coordinate is rotated from the geographic longitude-latitude
so that the model North Pole is located in
Greenland. To couple this rotated ocean with nonrotated
atmosphere, a new flux coupler has been developed.
The new coupler transfers geographically distributed
variables between the irregularly corresponding
atmospheric and oceanic grids, with attention paid to
area conservation (Fig.).
including Asian monsoon precipitation pattern and
radiation budget.
c. Long-term Integration of the Ocean Model
The ocean model with our target resolution has been
integrated for years. The model is forced by surface
stress and heat and freshwater flux boundary condition,
without any restoring to realistic sea surface
temperature or salinity. While realistic intensity of
NADW is reproduced, unrealistic deep convection in
the Antarctic Ocean, which would be partly due to
unrealistic forcing data, is identified.
d. Code Optimization of the Climate Model
In order to enhance the efficiency of the model run
on the Earth Simulator, optimization of the model code
has been done. As a result, the coupled model runs on
nodes of the Earth Simulator with reasonable computational
performance (. TFLOPS).
b. Improvement and Tuning of the Atmospheric Model
Because of the inherent uncertainty residing in parameterizations,
an increase in the resolution of climate
models does not always result in the improved climate
reproducibility. This is especially the case for the
atmospheric part, in which complex moist processes
are parameterized. We have, thus, conducted more
than cases of test run of the T atmospheric
model improving parameterizations and tuning uncertain
parameters. This process results in improved climate
reproducibility of the model in multiple aspects,
e. Experiments with a Medium-resolution Climate
Model
A medium resolution version of the coupled oceanatmosphere
model is utilized to gain the experience of
coupling without flux correction in advance of the
high-resolution model experiments. A control experiment,
in which greenhouse gas concentrations are kept
fixed to the present level, and a transient climate
change experiment, in which CO concentration is
increased by % per year compounded, are successfully
done. The model does not show serious climate drift
in the control run.
Fig.29 Sea surface temperature distribution calculated by the highresolution
ocean model (shown in the rotated coordinate).
Subject 2: Development of Integrated Earth System
Model for Global Warming Prediction
a. Development of a Coupled Carbon Cycle – Climate
Change Model
a-. Terrestrial Carbon Cycle Model
This group develops a model that estimates the carbon
budget of terrestrial ecosystems, which may exert
short- to long-term effects on atmospheric carbon diox-
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