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Volume 41 (1985)
- Issue 6 Pages 373-
- Issue 5 Pages 283-
- Issue 4 Pages 199-
- Issue 3 Pages 135-
- Issue 2 Pages 65-
- Issue 1 Pages 1-
Volume 41, Issue 3
Displaying 1-7 of 7 articles from this issue
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Subsurface Temperature Observations near the Bay HeadMasaji Matsuyama1985 Volume 41 Issue 3 Pages 135-144
Published: July 25, 1985
Released on J-STAGE: June 17, 2011
JOURNAL FREE ACCESSLong-term temperature measurements of the subsurface layer near Uchiura-Bay head were made in summer 1978 and 1979 to further investigate the characteristics of the internal tides in more detail. The temperature measurements indicate that the internal tides were present at all times during the observational period. The semidiurnal internal tides are usually dominant over the diurnal, but at times the diurnal internal tides have comparable amplitudes with the semidiurnal. When the semidiurnal internal tides are predominant, the fundamental period of the longitudinal internal seiche in Uchiura Bay estimated from the observed density structure is close to the semidiurnal period. However, the reason for the occasional amplification of the diurnal internal tides is not clear.View full abstractDownload PDF (1452K) -
Masaji Matsuyama1985 Volume 41 Issue 3 Pages 145-156
Published: July 25, 1985
Released on J-STAGE: June 17, 2011
JOURNAL FREE ACCESSNumerical experiments were performed to explain the observed results of the internal tides in Uchiura Bay. The experiments for the generation of the internal tides in Suruga Bay indicate that the internal tides, generated at the slopes in the bay, are not as large an amplitude as those observed in Uchiura Bay. However, when the semidiurnal internal tides incident through the mouth of Suruga Bay are considered, they are amplified. The amplitude at the head of Uchiura Bay is 6-12 times larger than that at the mouth of Suruga Bay under the summer density structure. Under the fall density structure, the amplitude ratio is approximately 4-6. The amplification of the semidiurnal internal tides in Uchiura Bay is considered to be due to resonance of the longitudinal internal seiche of Uchiura Bay. On the other hand, the calculated diurnal internal tides are not as large as those observed. Therefore, the diurnal internal tides are thought to already have these large amplitudes at the mouth of Suruga Bay.
Therefore, from the observations and numerical experiments, it is concluded that the internal tides observed in Uchiura Bay are mostly the internal tides originating from the outer region of Suruga Bay, and the semidiurnal tides are the internal seiche which is resonantly amplified.View full abstractDownload PDF (1773K) -
Part 1. Measurements and Calculations of Area-Averaged Divergence and VorticityHideo Kawai1985 Volume 41 Issue 3 Pages 157-166
Published: July 25, 1985
Released on J-STAGE: June 17, 2011
JOURNAL FREE ACCESSTo area-average the horizontal divergence and the vertical component of vorticity, three methods are proposed and examined. The polygon method is based on deformations of a polygon made by connecting drifters. They are deployed at widely different scales of 1cm-1, 000 km and tracked using various procedures. The loop method is adopted when a drifter completes at least two loops of trajectory in a tidal vortex, a ring or a gyre. Even if data for a drifter completing only one loop is available, the vorticity can be calculated. The crossing method is applied to the GEK data on the circumference of a Kuroshio ring. The data which will be used to calculate them in Part 2 are summarized in tables. Offset dispositions of positive and negative divergences or vorticities on a horizontal plane and in a water column are shown. Probably, the vertical offset of vorticities does not occur in general. The area-turnover of a polygon of drifters are discussed. Sampling time-intervals, appropriate to the scale of the area, for the polygon and loop methods are examined. A first impression of Rhines'(1979) sketch has produced a misunderstanding that the polygon method would be useless because a limited number of drifters cannot follow such a complicated deformation of the material line over a long period. It is shown that adopting a short time-scale appropriate to the length scale furnishes a practical solution to the problem.View full abstractDownload PDF (1542K) -
Part 2. Results and InterpretationHideo Kawai1985 Volume 41 Issue 3 Pages 167-175
Published: July 25, 1985
Released on J-STAGE: June 17, 2011
JOURNAL FREE ACCESSAn attempt is made to find relations of ensemble averages of Q2/2 and ζ2/2 to length scale, L, where Q and ζ are the area-averaged horizontal divergence and vertical component of vorticity, respectively. To calculate Q and ζ the polygon, loop and crossing methods have been used in Part 1. Here L is the square root of an area of a polygon connecting drifters or of a domain enclosed by a looping trajectory or by a closed integration curve. In the light of an extended -5/3 power law for energy spectrum, the ensemble averages of Q2/2 and ζ2/2 are shown to be proportional to L-4/3 not only in the three-dimensionally isotropic range but also in the mesoscale range (3m≤30km). They approach constants at microscales (L≤1cm), and become proportional to L-2 at macroscales (L≥100 km). By the polygon method, unbiased random samples of Q2/2 and ζ2/2 are liable to be drawn from a population. By the loop and crossing methods, the same is true of Q2/2, but samples of ζ2/2 much greater than the average are to be drawn for the following reason. The loop and crossing methods are intentionally applied to vortices of various scales from a tidal vortex to the Antarctic Circumpolar Gyre. Since vorticity is locally concentrated within vortices and shear zones distributed intermittently, the loop and crossing methods always catch greatest values of vorticity but the polygon method does not. Values of Q2/2 and ζ2/2 at 30 m depth are reduced, at the lowest, to one hundredth of those at the surface. Those around the Kuroshio are, at the highest, one hundred times those in the eastern North Pacific.View full abstractDownload PDF (1543K) -
Yasuo Matsukawa, Satsuki Matsumura1985 Volume 41 Issue 3 Pages 176-180
Published: July 25, 1985
Released on J-STAGE: June 17, 2011
JOURNAL FREE ACCESSA peculiar dispersion of salt, which was found in a partially mixed estuary by long-term continuous measurements of current and salinity and directed outward in the upper layer and inward in the lower layer in summer, is reported and discussed. The cause is estimated to be salinity stratification and wind-driven fluctuations in water near the coast. The general formulation is presented and a great possibility of negative dispersion against the horizontal gradient is pointed out. Dispersion coefficients are also estimated.View full abstractDownload PDF (708K) -
Keisuke Taira, Toshihiko Teramoto, Shoji Kitagawa1985 Volume 41 Issue 3 Pages 181-192
Published: July 25, 1985
Released on J-STAGE: June 17, 2011
JOURNAL FREE ACCESSYear long measurements of bottom pressure were made at 2, 036 m depth in Sagami Trough, at 2, 538 m depth in Suruga Trough, and at 32 m depth in the south of Minami-Daitojima Island. Amplitudes and phase lags of the major constituents of tides were estimated by the response method, and they were compared with the observational results at several tide stations operated by the Japan Meteorological Agency. A comparison with Schwiderski's global models for the eight tidal constituents showed that the amplitudes were in good accordance to one another within 3 cm, and that the differences of phase lags were less than 15°. The largest portion of the variations of the bottom pressure was caused by the tides: the variance of the major eight constituents was more than 98. 5% as large as the total variance. The measurements show that tidal waves can be recorded offshore with a sufficient accuracy by the quartz sensors. Drifts of indication of the pressure gauges were significant and they prevented detection of a long-term variation which might be caused by fluctuations of the ocean currents or by the eddies.View full abstractDownload PDF (1969K) -
Katsuhiko Matsunaga, Kazuo Abe1985 Volume 41 Issue 3 Pages 193-197
Published: July 25, 1985
Released on J-STAGE: June 17, 2011
JOURNAL FREE ACCESSThe relationship between Cd and PO4 in the Kuroshio and Oyashio regions and the Okhotsk Sea was examined. The resultant equations are as follows: Cd (ngl-1) =37.0 PO4 (μM) + 2.6; Cd (ngl-1) =32.1 PO4 (μM) +1.2 and Cd (ngI-1) =34.1 PO4 (μM) +7.9, respectively. These results are in good agreement with previously reported studies, and indicate that during removal from surface waters to deeper waters by biological assimilation and regeneration in deeper waters Cd and PO4 maintain the same ratio in the open ocean. The relationship between Cd and PO4 in coastal waters, however, differed from that in the open ocean.View full abstractDownload PDF (647K)
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