Detecting fluctuations of the Kuroshio axis south of Japan using TOPEX/POSEIDON altimeter data   总被引：1，自引：0，他引：1  

Shiro Imawaki  Mayumi Gotoh  Hiroyuki Yoritaka  Noriya Yoshioka  Atsunobu Misumi 《Journal of Oceanography》1996,52(1):69-92

Sea surface dynamic topography (SSDT) can be divided into temporal mean SSDT and fluctuation SSDT. The former is approximated with a climatological mean SSDT and the latter is derived from satellite altimetry data, to give an approximated total SSDT (called a composite SSDT). The method is applied to detecting fluctuations of the Kuroshio axis south of Japan using TOPEX/POSEIDON altimeter data from the first year mission in 1992–1993. The fluctuation SSDT averaged over a wide area south of Japan clearly shows an annual cycle with an amplitude of about 15 cm. Temporal changes of SSDT along a subsatellite track crossing the Kuroshio compare moderately well with those estimated from repeated hydrographic observations, although there is a discrepancy of unknown origin. The composite SSDT also compares well with SSDT estimated from the same hydrographic data. Horizontal distribution of the surface geostrophic velocity component normal to subsatellite tracks is derived every ten days from the composite SSDT. Most locations of estimated strong eastward geostrophic velocities coincide well with locations of the Kuroshio axis determined every 15 days fromin situ surface velocity measurements on various vessels; for example, a fairly large meander of the Kuroshio south of Honshu is clearly detected. It is concluded that the composite SSDT can be used reliably to detect fluctuations of the Kuroshio axis south of Japan.  相似文献   

Assimilation of Satellite Altimetry into a Western North Pacific Operational Model     

Masafumi Kamachi  Tsurane Kuragano  Noriya Yoshiok  Jiang Zhu  Francesco Uboldi 《大气科学进展》2001,18(5):767-786

l. IntroductionLinear dynamics ls domlnant as a response to atmospheric forcing in the equatrialregion. In the mid-- to high--latitudes, ocean represents nonlinear phenomena such as strongcurrents and meso--scale eddies. Heat and water fluxes are also important. The resultantscales of the phenomena are rather small. We developed, for the mid-- to high--latitudes, anocean data assimilation system COMPASS--K: Comprehensive Ocean ModeIing, Prediction,Analysis and Synthesis System in the K…  相似文献   

Observation of the abyssal current in the West Mariana Basin   总被引：1，自引：1，他引：1  

Noriya Yoshioka  Masahiro Endoh  Hiroshi Ishizaki 《Journal of Oceanography》1988,44(1):33-39

In order to investigate long-term variations of deep sea currents and temperature in the western North Pacific, a direct current measurement was made at 12.5°N, 137°E from July 1985 to July 1986. The current meter was moored at a depth of about 4,000 m (bottom depth 4,604 m) in the West Mariana Basin, very close to the deep water passage to the North Pacific Basin. Throughout the observed period, the current flows southward with an average speed of 0.8 cm sec^–1. There are significant variations of both currents and temperature within the period of 60 days. For the shorter time scales, in addition to the tidal oscillations with one day and half day periods, there is a notable spectral peak of the current with a clockwise rotation at a period of 2.2 days, which is slightly shorter than the local inertial period of 2.3 days.The observed southward current seems to indicate that the deep sea water in the West Mariana Basin flows out through the sill which is deeper than 4,000 m and is located about 200 km southeast of the mooring point. A simple analysis of the linear plane wave indicates that the medium time-scale variation with a period of 60 days is associated with the barotropic Rossby wave whose wavelength is 390 km and whose trough direction is 30° clockwise from the north.  相似文献