Eingang zum Volltext in OPUS
Hinweis zum Urheberrecht
Dissertation zugänglich unter
Analysis of the Circulation on the East-Chinese Shelf and the adjacent Pacific Ocean
Dokument 1.pdf (6.967 KB)
JEBAR, Kuroshio, long-term hindcast
Sündermann, Jürgen (Prof. Dr.)
Tag der mündlichen Prüfung:
Kurzfassung auf Englisch:
The East-Chinese Shelf (or North East Asian Regional seas - NEAR-seas) has the broadest shelf waters and the most complicated topography in the world. With the through-flow of one of the two largest western boundary currents - the Kuroshio - it provides an ideal case to investigate the water exchange mechanisms between shelf waters and oceanic waters, the variability of channel transports and the Joint Effect of Baroclinicity and Relief (JEBAR).
In this work, a regional numerical model has been established and a 44-year hindcast study is accomplished with the surface flux dataset derived from ERA40 reanalysis in the NEAR-seas from 1958 to 2001. The numerical model is based on the parallelised HAMburg Shelf Ocean Model (P-HAMSOM) and features a high resolution both vertically and horizontally. The systematic verification of the regional model proves that its performance is successful, the validation data used spans from historical data of ship cruises to remote sensing data of satellite. It is expected that a nested strategy to provide more realistic inflow boundaries and an embedded ice model dealing with the ice process in northern Japan Sea will surely improve the hindcast.
The Kuroshio and its branch currents system of the NEAR-seas is investigated by means of three approaches. An extensive analysis of the WOCE/SVP KRIG data from 1989 to 1999 reveals the surface current pattern in the NEAR-seas. A tracer model is designed to simulate the trajectories derived from the satellite tracked Lagrangian drifters. The tracer model successfully reproduces these drifter trajectories. This is a validation of the hindcast model from a different point of view by means of totally independent data. For the first time, the existence of a large eddy east of the Ryukyu archipelago is demonstrated.
The second approach is the analysis of the ocean temperature, salinity and currents based on the model generated variable fields in the NEAR- seas. The characteristics of the climatological SST and SSS distribution are summarized. The existence of the HBCW (Huanghai Bottom Cold Water) is demonstrated and its structure in summertime is described.
The vorticity balance in the NEAR-seas is examined and the JEBAR and its role on the East-Chinese Shelf is analyzed extensively. According to this study, JEBAR is formulated as an arithmetically generated term in the final vorticity equation. It can be a correction term to the vorticity balance only when the velocity field is in a quasi-stationary state. Many earlier works take the JEBAR for mechanism to force the currents in the real ocean. This is, however, an incorrect application of the JEBAR term. The JEBAR can only be used as a forcing term when the currents are examined in a pure diagnostic way, but even in this case it is not really forcing mechanism. The maximum and minimum of the JEBAR distribution on the East-Chinese Shelf correlates well with the shelf breaks or straits where strong currents exist. The JEBAR plays an important role in the depth-averaged vorticity balance along shelf breaks and straits where the JEBAR is two orders of magnitude larger than other vorticity terms, while it plays a minor role in shallow shelf waters.