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Ocean Surface Topography from Space
SCIENCE
Variations of sea surface height and flow fields in the western North Pacific and surrounding marginal seas


Author:

Kaoru Ichikawa - (Research Institute for Applied Mechanics, Kyushu University)

Co-Investigator(s):
  Yoichi Fukuda
Hiroyuki Yoritaka
Akihiko Morimoto
Naoto Ebuchi
Yoshiaki Tamura
Yosuke Fujii
Tsurane Kuragano
Osamui Soguchi
Hiroshi Uchida
Shinichi Ito
(Department of Geophysics, Graduate School of Science, Kyoto University)
(Hydrographic and Oceanographic Department, Japan Coast Guard)
(Hydrospheric Atmospheric Research Center, Nagoya University)
(Institute of Low Temperature Science, Hokkaido University)
(Mizusawa VERA Observatory, National Astronomical Observatory of Japan)
(Oceanographic Research Department, Meteorological Research Insititute)
(Oceanographic Research Department, Meteorological Research Insititute)
(Remote Sensing Technology Center of Japan)
(Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology)
(Tohoku National Fisheries Research Institute, Fisheries Research Agency)

Abstract:

Variations of sea surface height and flow fields in the western North Pacific and surrounding marginal seas
Current Systems in the western North Pacific and surrounding marginal seas. Their variations are monitored by in situ observations (yellow lines), ocean radars (green areas) and drifters, together with satellite altimeters. Comparisons with gravity changes and development of better data assimilation models are also conducted in this project.
This proposal to participate in the Ocean Science Topography Science Team (OST-ST) is an extension of the latest Jason-2 Mission Award entitled as "Variability of the flow fields in the western North Pacific and surrounding marginal seas" (PI: Kaoru Ichikawa). We have achieved many descriptive physical oceanographic results on variations of flow fields in the western North Pacific, including the Kuroshio, Kuroshio Extension and Oyashio current systems and their variations induced by mesoscale eddies. In addition, we have extended our description to include currents in marginal seas as the East China Sea and Sea of Okhotsk. Furthermore, apart from those basic researches, the ocean data assimilation system is in operation on the real-time basis by the Japan Meteorological Agency to provide real-time products everyday through the Japan-GODAE products server.

The primary aim of this proposal is to extend our understanding of the sea height and flow fields in the western North Pacific and surrounding marginal seas. Heat and volume transport of the Kuroshio and Oyashio current systems will be investigated by combining altimetry data with in situ ob- servations and numerical models. Similarly, currents in marginal seas around Japan such as the Japan Sea and the Sea of Okhotsk will be described by combination of the altimeter data and in situ observations, including surface drifters. Variations of those currents in the marginal seas would be related to the Kuroshio and Oyashio current systems in the western North Pacific, but their direct observational evidences have not been sufficiently shown yet, due to difficulty related to their small-scale nature in the marginal seas. Especially, in the straits connecting to those marginal seas, where the depth is shallow and lands are close, our use of the altimetry data is significantly limited since their accuracy is quite poor. Use of the High-Frequency (HF) ocean radar data with high spatio-temporal resolutions and improved accuracy of the altimetry data in marginal seas together with dense coverage by multi-satellite use would provide better insights of such variations.

In this proposal, we shall continue in situ observations. They include hydrographic and mooring field observations, HF radars, and drifters. They are used for basic oceanographic studies, and may be eventually used as calibration/validation data for Jason-2/OSTM by any other OST-ST groups. Similarly, we shall maintain operational real-time Japan-GODAE data products produced by operating an ocean data assimilation system of Japan Meteorological Agency (JMA). Meanwhile, assimilated results from a more comprehensive model will be used for basic studies. In addition, gravity changes due to huge oceanic motions such as a large Kuroshio meander will be examined by use of a dense network of accurate gravity field measurements in Japan. We intend to obtain new understandings of circulations in the western North Pacific through those aspiring studies.



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