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1.
The study of the Kuroshio in the East China Sea and the currents east of the Ryukyu Islands 总被引：3，自引：0，他引：3
In this study, the inverse method is used to compute the Kuroshio in the East China Sea and southeast of Kyushu and the currents east of the Ryukyu Islands, on the basis of hydrographic data obtained during September-October, 1987 by R/V Chofu Maru. The results show that: (1)A part of the Taiwan Warm Current has a tendency to converge to the shelf break; (2) the Kuroshio flows across the section C3 (PN) with a reduced current width, and the velocity of the Kuroshio at the section C3 increases and its maximum current speed is about 158 cm/s, and its volume transport here is about 26×106m3/s; (3) the Kuroshio has two current cores at the sections C3 (PN) and B2 (at the Tokara Strait); (4) the currents east of the Ryukyu Islands are found to flow northward over the Ryukyu Trench during September-October, 1987. The velocities of the currents are not strong throughout the depths. At the section C2 east of the Ryukyu Islands, the maximum current speed is at the 699 m levei and its magnitude is 25 cm/s, and i 相似文献
2.
Simulation of Formation and Spreading of Salinity Minimum Associated with NPIW Using a High-Resolution Model 总被引：1，自引：2，他引：1
A series of numerical experiments were conducted with a high-resolution (eddy-permitting) North Pacific model to simulate
the formation and spreading of the salinity minimum associated with the North Pacific Intermediate Water (NPIW). It was found
that two factors are required to simulate a realistic configuration of the salinity minimum: a realistic wind stress field
and small-scale disturbances. The NCEP reanalyzed wind stress data lead to better results than the Hellerman and Rosenstein
wind stress data, due to the closer location of the simulated Oyashio and Kuroshio at the western boundary. Small-scale disturbances
formed by relaxing computational diffusivity included in the advection scheme promote the large-scale isopycnal mixing between
the Oyashio and Kuroshio waters, simulating a realistic configuration of the salinity minimum. A detailed analysis of the
Oyashio water transport was carried out on the final three-year data of the experiment with reduced computational diffusivity.
Simulated transport of the Kuroshio Extension in the intermediate layer is generally smaller than the observed value, while
those of the Oyashio and the flow at the subarctic front are comparable to the observed levels. In the Oyashio-Kuroshio interfrontal
zone the zonally integrated southward transport of the Oyashio water (140–155°E) is borne by the eddy activity, though the
time-mean flow reveals the existence of a coastal Oyashio intrusion. In the eastern part (155°E–180°) the zonally integrated
transport of the Oyashio water indicates a southward peak at the southern edge of the Kuroshio Extension, which corresponds
to the branching of the recirculating flow from the Kuroshio Extension.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
High parallelization efficiency in barotropic-mode computation of ocean models based on multi-grid boundary ghost area 总被引：1，自引：0，他引：1
In general, barotropic-mode computation requires the largest communication time in ocean models because of its iterative nature, when parallel computation is performed based on regional partitioning. In this study, reduction in the overhead time included in the communication in the parallel computation of the barotropic mode is considered to achieve a high parallelization efficiency of ocean models. We verify that the reduction in the communication frequency based on the multi-grid boundary ghost area reduces the total communication time. We find that this is because the sum of several kinds of overhead time for communication occupies a fairly large part of the total communication time. We discuss the trade-off between the decrease in communication time and the increase in computation time due to increased boundary area in such cases, leading to a determination of a suitable width of the multi-grid boundary that minimizes the total required time. We also discuss the efficiencies of the one- and two-dimensional partitioning of the model domain, when a multi-grid boundary is used. In general, two-dimensional partitioning is more efficient than one-dimensional for large partitioning numbers. 相似文献
4.
Ryoko Tokeshi Kaoru Ichikawa Satoshi Fujii Kenji Sato Shoichiro Kojima 《Journal of Oceanography》2007,63(4):711-720
A method to extract geostrophic current in the daily mean HF radar data in the Kuroshio upstream region is established by
comparison with geostrophic velocity determined from the along-track altimetry data. The estimated Ekman current in the HF
velocity is 1.2% (1.5%) and 48° (38°)-clockwise rotated with respect to the daily mean wind in (outside) the Kuroshio. Furthermore,
additional temporal smoothing is found necessary to remove residual ageostrophic currents such as the inertial oscillation.
After removal of the ageostrophic components, the HF geostrophic velocity agrees well with that from the altimetry data with
rms difference 0.14 (0.12) m/s in (outside) the Kuroshio. 相似文献
5.
6.
This paper presents results of observation and analysis of the response of one of the longest cable-stayed bridges in the world to the Hyogoken–Nanbu (Kobe) Earthquake of 17 January 1995. It is determined that interaction of the foundations of the bridge towers with the supporting soil plays a decisive role in the overall structural behaviour. The key factor governing the changes of the soil properties at this site is pore-water pressure buildup, which results in liquefaction of the saturated surface soil layers under large dynamic loads. Models of the soil and structure are created and initially validated by accurately simulating the system response to a small earthquake. Soil parameters reflecting the pore-water pressure buildup in the strong earthquake are determined by an advanced non-linear effective stress analysis, combining the Ramberg–Osgood model of stress–strain dependence with a pore pressure model based on shear work concept. They are utilized to investigate and simulate the interaction of the foundation and the supporting soil using the program SASSI with the flexible volume substructuring approach. The results show a good agreement with the observations and have useful implications to the scientific and engineering practice. © 1998 John Wiley & Sons, Ltd. 相似文献
7.
Y.?FujiiEmail author M.?Kamachi S.?Matsumoto S.?Ishizaki 《Pure and Applied Geophysics》2012,169(3):579-594
This paper investigates the feasibility of an ocean data assimilation system to analyze the salinity variability associated with the barrier layer in the equatorial Pacific. In order to validate reproducibility of the temperature and salinity fields, we perform an assimilation run where some temperature and salinity observations by TRITON buoys and Argo floats are withheld. The assimilation run reproduces interannual variability of salinity in the equatorial Pacific exhibited in the data that are withheld. Statistics shows that salinity values and variations in the assimilation run are closer to the data than the climatology and in the model free run. We also confirm that zonal currents in the equatorial Pacific in the reanalysis, where all available temperature and salinity data are assimilated, are consistent with an observation-based mapping and the data of the Acoustic Doppler Current Profiler mounted on TAO buoys. Variability of the barrier layer and relevant salinity field in the reanalysis is consistent with former studies. A thick barrier layer area generally exists west of the equatorial salinity front and is displaced zonally with the migration of the front in the response to El Niño-Southern Oscillation, although the area moved to the east over the front in the 1997 El Niño. It is confirmed that the barrier layer thickness is closely correlated with the near-surface temperature in the equatorial Pacific. 相似文献
8.
A new method was developed to compare the classifications of different kind of data maps based on the self-organizing map (SOM) analysis. The surface current maps of the northern coast of Ishigaki and Iriomote Islands, East China Sea, observed by high-frequency (HF) radar were classified by SOM. Winds, sea surface temperatures (SST), and reanalysis data were also classified by SOM. The optimum area for classification was determined objectively by the new method, which relates these patterns to HF radar current patterns. We found two typical surface patterns: the first was that northeastward flows are dominant in the observation area and the second was that a clockwise eddy was also dominant in this area. The southwestward wind pattern was strongly related to the dominant clockwise eddy pattern of the HF radar current field. 相似文献
9.
Norihisa?UsuiEmail author Shiro?Ishizaki Yosuke?Fujii Masafumi?Kamachi 《Journal of Oceanography》2011,67(3):253-262
We assess validity of a Gaussian error assumption, the basic assumption in data assimilation theory, and propose two kinds
of constraints regarding non-Gaussian statistics. In the mixed water region (MWR) off the east coast of Japan exhibiting complicated
frontal structures, a probability density function (PDF) of subsurface temperature shows double peaks corresponding to the
Kuroshio and Oyashio waters. The complicated frontal structures characterized by the temperature PDF sometimes cause large
innovations, bringing about a non-Gaussianity of errors. It is also revealed that assimilated results with a standard three-dimensional
variational (3DVAR) scheme have some issues in MWR, arising from the non-Gaussianity of errors. The Oyashio water sometimes
becomes unrealistically cold. The double peaks seen in the observed temperature PDF are too smoothed. To improve the assimilated
field in MWR, we introduce two kinds of constraints, J
c1 and J
c2, which model the observed temperature PDF. The constraint J
c1 prevents the unrealistically cold Oyashio water, and J
c2 intends to reproduce the double peaks. The assimilated fields are significantly improved by using these constraints. The
constraint J
c1 effectively reduces the unrealistically cold Oyashio water. The double peaks in the observed temperature PDF are successfully
reproduced by J
c2. In addition, not only subsurface temperature but also whole level temperature and salinity (T–S) fields are improved by
adopting J
c1 and J
c2 to a multivariate 3DVAR scheme with vertical coupled T–S empirical orthogonal function modes. 相似文献
10.
Shoichiro Fukao Manabu D. Yamanaka Hiromasa Matsumoto Toru Sato Toshitaka Tsuda Susumu Kato 《Pure and Applied Geophysics》1989,130(2-3):463-479
Vertical and temporal variations of three-dimensional wind velocity associated with an upper-tropospheric cold vortex-tropopause funnel system were observed by an MST radar in Japan (the MU radar). Marked changes of vertical velocity and horizontal wind direction were found between the inside and outside of the cold vortex. The vertical velocity activity outside the vortex was asymmetric; it was most active in a sector before the vortex. Unsaturated internal gravity waves in their generation stage contribute predominantly to the vertical velocity activity, suggesting that tropospheric occluded cyclones may be a possible source of middle-atmospheric gravity waves through the geostrophic adjustment process. 相似文献