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| Titel |
Long-term modulations of mesoscale eddy activities in the Kuroshio-Oyashio confluence zone represented in a high-resolution coupled model, and further model development toward better predictions |
| VerfasserIn |
Hiroaki Tatebe, Masao Kurogi, Tatsuo Suzuki, Yukio Tanaka, Hiroyasu Hasumi, Masayoshi Ishii, Masahide Kimoto |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048372
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| Zusammenfassung |
| For predicting a near-term climate up to year 2030 towards contributing to the 5-th
assessment report of the IPCC, decadal hindcast/forecast experiments are in progress using
MIROC4 developed at AORI/NIES/JAMSTEC with very high horizontal resolutions (atm. :
T213, ocn.: 1/4Ë x 1/6Ë ). In the initialization procedures, historical ocean subsurface data
are assimilated into the ocean model. In this regard, mesoscale oceanic eddies in the model
are filtered out in calculating analysis increments. This approach is used to assimilate
only basin-scale and long-term variations resolved in the observational data and to
generate high-frequency eddies physically in response to background currents and
hydrographic structures. In the assimilation experiment, the interannual to decadal
modulations of high frequency eddy activities in the Kuroshio-Oyashio interfrontal zone
(KO zone) are represented reasonably as seen in observations, and in addition,
the modulations seem to be predicted in a few cases of the hindcast experiments.
The eddies in the KO zone are known to play an important role in transporting
nutrient, large zooplanktons, and water masses in the subarctic North Pacific to the
subtropics and in forming North Pacific Intermediate Water. The present results
imply possibility in predicting ecosystem variations in the KO zone. However, such
very high resolution modeling costs too much computational resources and thus a
number of ensemble members for assimilations and predictions which is tightly
linked with prediction skill is restricted. To solve this problem, we are modifying the
climate model MIROC5, the latest version of MIROC, to incorporate a nested ocean
model focused on the KO zone. The horizontal resolutions of the nested ocean
model, global atmosphere, and ocean models are 0.2Ë , T42, and 1Ë , respectively.
This configuration is set just for preliminary experiments. At this stage, MIROC5
with the nested ocean model is integrated successfully for 30 years, and there are
no significant trends in the global mean sea surface temperature and surface air
temperature. In the KO zone where the nest model is adapted, the sharp meridional
gradient of the SST associated with the Kuroshio Extension front and the Oyashio
(or the subarctic) front are represented and mesoscale eddies spawned from the
unstable fronts can be seen. The coupled model with the nested ocean model focused
on some specific regions requires much smaller computational resources than the
global high-resolution coupled model, and therefore it may be a powerful tool for
predicting current and hydrographic structures, and furthermore ecosystem variations. |
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