Atmospheric Modeling
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The CCSR/NIES AGCM, developed through the cooperative work of CCSR and
NIES (National Institute for Environmental Studies), has been used for
various studies on climate dynamics, including simulations of climate
change and numerical experiments concerning the mechanisms of climate
variability.
The atmospheric general circulation model (AGCM) is a computer program
which simulates the global atmosphere. It calculates the evolution,
over time, of the state of the atmosphere, considering various
physical processes. Providing precise treatments of radiation and
cloud processes is a notable characteristic of the CCSR/NIES AGCM.
Atmospheric General Circulation Model (Figure1)
By comparing the results of AGCM integrations using observed sea surfacetemperature (SST) as its boundary condition, we found that the model reproduces the atmospheric interannual variability corresponding to the El Nino cycles. This type of experiment is useful not only in verification of the AGCM, but also in studies on the mechanisms of climate variability, as the model provides various information which supplements insufficient observations.
[Figure 2]: Correlation between sea surface temperature (SST)
in the eastern Pacific and outgoing longwave radiation (OLR);
model (upper figure) and observation (lower figure).
By using various boundary conditions different from the present state of the Earth, we can investigate the atmospheric state under a number of conditions. These numerical experiments are a very effective way of studying the mechanisms of climate change.
[Figure 3]: Simulated temperature and wind field in the last maximum glacial period; the differences from the current state are shown.
The land surface is an important subsystem of the climate system, and the the amount of snow and water in soil is considered one of the key parameters in climate change. The variability of the amount of soil moisture and snow, which cannot be easily estimated from direct observations, has become accessible through the use of a land-surface model driven by observed atmospheric data.
[Figure 4]: Distribution of soil moisture estimated by a land-surface model calculation using observed rainfall and atmospheric state as input data.
The existence of water and its cycle characterizes a unique feature of Earth's climate. Combining AGCM experiments and satellite data, the roles of the water cycle in the climate are being investigated considering the interactions among clouds, radiation, and large-scale dynamic processes.
[Figure 5]: Estimated distribution of three kinds of water originating in the Atlantic, Indian, and Pacific Oceans.
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