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431.
Matsuno and Nagata (1987) showed numerically that the spreading characteristics of the discharged heated water from power plants of existing scale is significantly influenced by the earth's rotation effect. Although the effect of the enhancement of the Coriolis parameter on the spreading characteristics of the formed warm water mass was discussed in order to demonstrate the rotation effect, other parameters such as the density difference between the discharged heated water and ambient water and the vertical eddy viscosity and diffusivity were fixed. In this paper, the dependence of the spreading characteristics on these parameters is examined. Then, it is shown that the overall shape of the formed warm water mass and density and velocity structure strongly depend on these parameters. Also, it is indicated that the behavior of the warm water mass under the rotation effects is too complicated to be described with a few parameters. For example, the internal radius of deformation seems to be one of the determinative parameters, and the increase of the density difference between discharged water and ambient water has a similar effect on the shape of the formed warm water mass as a decrease of the Coriolis parameter. However, a change of the two values has different effects on the detailed density structure and current structure of the warm water mass. The Prandtl number seems to determine some aspects of the veloczty field such as velocity magnitude and width of the southward flowing current zone. However, other features such as the thickness of the warm water mass are not determined by the Prandtl number. 相似文献
432.
Intrusion of less saline shelf water into the Kuroshio subsurface layer in the East China Sea 总被引:7,自引:0,他引:7
Atsuhiko?IsobeEmail author Eiji?Fujiwara Pil-Hun?Chang Koichi?Sugimatsu Manabu?Shimizu Takeshi?Matsuno Atsuyoshi?Manda 《Journal of Oceanography》2004,60(5):853-863
The possible origin and cause of the less saline shelf water detected in the Kuroshio subsurface layer around the shelf edge
of the East China Sea are investigated using observational results obtained in May 1998–2001 in conjunction with a dataset
archived by Japan Oceanographic Data Center and a numerical model. The observations show that subsurface intrusions of less
saline water are always detected in May in layers above 24.5σθ isopycnal surface, and that salinity inversions (i.e., areas
in which the less saline water lies beneath the saline water) are detected around the trough of the Kuroshio frontal eddy
(or wave). Analyses of the archived dataset reveal that the isopycnal surface of 24.5σθ is the deepest layer of the Kuroshio
pycnocline outcropping to the sea surface on the shallow shelf in early spring. Outcropping isopycnals above 24.5σθ encounter
a less saline water plume originating from the Changjiang, especially in the western East China Sea. Thereafter, the less
saline water moves along isopycnal layers and reaches the Kuroshio front around the shelf edge. Numerical models demonstrate
that, when the frontal wave captures the less saline water, the shelf water takes the form of a salinity inversion in the
trough because isohalines in the frontal wave have a phase lag between the upper and lower layers in consequence of the baroclinic
instability. 相似文献
433.
Tatsuki Toda Tomoko Okashita Takeshi Maekawa Bin Abdul Adzis Kee Alfian Mohd Kushairi Mohd Rajuddin Ryota Nakajima Wenxi Chen Kunio T. Takahashi Bin Haji Ross Othman Makoto Terazaki 《Journal of Oceanography》2007,63(1):113-123
Coral community structures at eleven fringing reef sites were investigated along the coast of Peninsular Malaysia. Estimated
coverage of coral communities is examined by applying quantitative digital image analysis to the line transect method. Four
coral community types were characterized by dominant genera and lifeforms: Acropora branching community, Montipora-Acropora community, Porites massive community, and Heliopora community. Live coral coverage in all study sites ranged from 17.9% to 68.6%. Most reefs were in “fair” condition while some
reefs were shown to be in “poor” condition. Coral community structures among the study sites were divided into the west coast
of Peninsular Malaysia with a dominant Porites massive lifeform, and the east coast with a variety of lifeform categories of Montipora and Acropora. Physical effects such as the monsoon wind regime and sedimentation are likely to influence the formation of dominant coral
communities around Peninsular Malaysia. 相似文献
434.
Y. Fukada S. Hayakawa I. Kasahara F. Makino Y. Tanaka H. Akiyama M. Matsuoka J. Nishimura M. Oda M. Nakagawa H. Sakurai V. S. Iyenger P. K. Kunte R. K. Manchanda B. V. Sreekantan 《Astrophysics and Space Science》1976,42(1):245-248
The size of the hard X-ray source in the Crab Nebula was observed with scintillation counters on board two balloons at a lunar occulatation on 24 January, 1975. The Gaussian width of the source is 34 (+17, –14) and the center thereof is offset from the pulsar by 6±4 at position angle 102°. The observed time profile can also be fitted to an alternative model of two line sources whose intensities are 48% at 11 and 25.5% at 7 on both sides of the pulsar.Paper presented at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975. 相似文献
435.
The evolution of coronal and chromospheric structures is examined together with magnetograms for the 1B flare of January 19, 1972. Soft X-ray and EUV studies are based on the OSO-7 data. The H filtergrams and magnetograms came from the Sacramento Peak Observatory. Theoretical force-free magnetic field configurations are compared with structures seen in the soft X-ray, EUV and H images. Until the flare, two prominent spots were connected by a continuous dark filament and their overlying coronal structure underwent an expansion at the sunspot separation rate of 0.1 km s–1. On January 19, the flare occurred as new magnetic fields emerged at 1019 Mx h–1 beneath the filament, which untwisted and erupted as the flare began. The pre-flare coronal emissions remained unchanged during the flare except for the temporary addition of a localized enhancement that started 5 min after flare onset. EUV lines normally emitted in the upper transition region displayed a sudden enhancement coinciding in time and location with a bright H point, which is believed to be near the flare trigger or onset point. The EUV flash and the initial H brightening, both of which occurred near the center of the activated filament, were followed by a second EUV enhancement at the end of the filament. The complete disruption of the filament was accompanied by a third EUV enhancement and a rapid rise in the soft X-ray emission spatially coincident with the disappearing filament. From the change of magnetic field inferred from H filtergrams and from force-free field calculations, the energy available for the flare is estimated at approximately 1031 erg. Apparently, changes in the overlying coronal magnetic field were not required to provide the flare energy. Rather, it is suggested that the flare actually started in the twisted filament where it was compressed by emerging fields. Clearly, the flare started below the corona, and it appears that it derived its energy from the magnetic fields in or near the filament.NCAR is sponsored by NSF. 相似文献
436.
437.
438.
Observations of the total lunar eclipse were made at 3.4-mm wavelength (87.4 GHz) on March 24, 1978. Eclipsr cooling curves with the best S/N ratio among those published thus far were obtained for the three points (the mountain area near the crater of Hipparuchus, Sinus Medii, and Copernicus). Each of the curves can be decomposed into the three parts which apparently correspond to ingress, totality, and egress. The derived cooling rate and heating rate differ significantly at the three points. 相似文献
439.
The staggered grid finite-difference method is a powerful tool in seismology and is commonly used to study earthquake source
dynamics. In the staggered grid finite-difference method stress and particle velocity components are calculated at different
grid points, and a faulting problem is a mixed boundary problem, therefore different implementations of fault boundary conditions
have been proposed. Viriuex and Madariaga (1982) chose the shear stress grid as the fault surface, however, this method has
several problems: (1) Fault slip leakage outside the fault, and (2) the stress bump beyond the crack tip caused by S waves
is not well resolved. Madariaga et al. (1998) solved the latter problem via thick fault implementation, but the former problem remains and causes a new issue;
displacement discontinuity across the slip is not well modeled because of the artificial thickness of the fault. In the present
study we improve the implementation of the fault boundary conditions in the staggered grid finite-difference method by using
a fictitious surface to satisfy the fault boundary conditions. In our implementation, velocity (or displacement) grids are
set on the fault plane, stress grids are shifted half grid spacing from the fault and stress on the fictitious surface in
the rupture zone is given such that the interpolated stress on the fault is equal to the frictional stress. Within the area
which does not rupture, stress on the fictitious surface is given a condition of no discontinuity of the velocity (or displacement).
Fault normal displacement (or velocity) is given such that the normal stress on the fault is continuous across the fault.
Artificial viscous damping is introduced on the fault to avoid vibration caused by onset of the slip. Our implementation has
five advantages over previous versions: (1) No leakage of the slip prior to rupture and (2) a zero thickness fault, (3) stress
on the fault is reliably calculated, (4) our implementation is suitable for the study of fault constitutive laws, as slip
is defined as the difference between displacement on the plane of z = + 0 and that of z = − 0, and (5) cessation of slip is achieved correctly. 相似文献
440.
Masaaki Okuda Hiroomi Nakazato Norio Miyoshi Takeshi Nakagawa Hiroko Okazaki Saneatsu Saito Asahiko Taira 《Island Arc》2006,15(3):338-354
Abstract The 250-m Choshi core (CHOSHI-1), drilled from hemipelagic muds of the Inubo Group, has been physically, geochemically and tephrochronologically analyzed back to 1 Ma. We provide pollen results for the 19–169 m section of the core (400–780 ka) bracketed by the marker tephra Ty1 (equivalent to J4) and the Brunhes–Matuyama paleomagnetic boundary. The results show good agreement with the corresponding oxygen isotope (δ18 O) profile, with high δ18 O intervals dominated by boreal conifers Picea , Abies , Pinus (subgen. Haploxylon ) and Tsuga ( diversifolia ), whereas low δ18 O intervals are dominated by temperate conifers Cryptomeria , Taxaceae-Cephalotaxaceae-Cupressaceae and Sciadopitys . In order to confirm pollen-climate relations for the relevant taxa, a modern surface pollen dataset for the Japanese archipelago was consulted. In this analysis, the ratios of Cryptomeria / Picea and temperate/boreal conifers serve as proxies for the 100-kyr glacial/interglacial cycle during the Middle Pleistocene. Distinct signals for marine isotope stages (MIS) 11, 12, 13–15, 16, 17 and 18–19 are recognized in accordance with the tephrochronology and δ18 O of the same core. Application of the criteria to an independent pollen record from Lake Biwa provides an integrated pollen stratigraphy for mid-latitude Japan during the past 800 ky. Some degree of uncertainty remains in the chronology of the MIS13–15 interval, relating to the uncertainty in the eruption age of widespread tephra Ks11. 相似文献