Variations of sea surface flow fields in the East Asian marginal seas and the western North Pacific
- (Research Institute for Applied Mechanics, Kyushu University)
The primary aim of this proposal is to extend our understanding of the surface flow fields in the western North Pacific and surrounding marginal seas. For currents in marginal seas around Japan (the East China Sea, the Japan Sea and the Sea of Okhotsk), the straits connecting to those marginal seas (i.e. the Taiwan Strait, the Tsushima Striat, the Tsugaru Strait and the Soya Strait) are most essential areas. Since the altimeters cannot properly work in those areas where the depth is shallow and lands are close, we have settled the High-Frequency (HF) ocean radar systems and Acoustic Doppler Current Profiler (ADCP) mounted on ferries crossing the straits to monitor variations of currents in each strait. We will accumulate these independent observations by data assimilation systems together with the altimetry data, to provide self-consistent observations. At the same time, we will conduct development of regional tidal models, modification of the altimeters retrieving algorithm, and the sea surface height measurements by Global Navigation Satellite System (GNSS) to assist satellite altimeters in coastal zones. Furthermore, we will also relate variations of those currents in the marginal seas to variations of the Kuroshio and Oyashio current systems in the western North Pacific, which will be investigated in parallel by combining altimetry data with in situ observations and numerical models.
In this proposal, we shall continue in situ observations. They include hydrographic and mooring field observations, HF radars, surface drifters, and bottom pressure gauges. They will be used for basic oceanographic studies, and may be eventually used as calibration/validation data for Jason-2/Jason-3 by any other OST-ST groups. Similarly, we shall maintain operational products of ocean monitoring and forecasting systems produced by Japan Meteorological Agency (JMA). Meanwhile, assimilated results from comprehensive models 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.