Circulation and Material Transport in Suo-Nada during Spring and Summer     

Rolando S. Balotro  Atsuhiko Isobe  Manabu Shimizu  Atsushi Kaneda  Takatoshi Takeuchi  Hidetaka Takeoka 《Journal of Oceanography》2002,58(6):759-773

An attempt was made to reproduce the circulation pattern in Suo-Nada, Japan during spring and summer season in order to elucidate the water exchange mechanism in the basin. Two hydrographic surveys at the end of each season were conducted covering the entire Suo-Nada area. A three-dimensional hydrodynamic Princeton Ocean Model (POM) was used to compute the current resulting from the observed density and wind field. During spring, a very pronounced counter clockwise gyre is situated near the opening of the basin. This is replaced by a clockwise circulation which seemed to occupy the whole domain during summer. Within each season, however, the vertical distribution of current does not show any remarkable differences, indicating the dominance of horizontal current and a very weak estuarine flow. These observational and numerical results were used to estimate the remnant function and the corresponding average residence time of permanently dissolved matter (PDM) and transformable matter (TM). The results revealed a small difference in the average residence times of materials within each season but a large seasonal variability between spring and summer. Furthermore, calculations based on climatological density fields have indicated a similar trend of variation between the seasonal values of average residence times. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Tidal pump at the shelf edge     

T. Yanagi  M. Shimizu  T. Saino  T. Ishimaru 《Journal of Oceanography》1992,48(1):13-21

Material transport through the shelf edge to the deep ocean determines the fate of particulate matter generated in productive coastal seas. In stratified estuaries, onshore flow in the bottom layer generally keeps particulate matter generated in the upper layer and settled down to the bottom layer within the estuaries. AT the shelf edge of Tokyo Bay under the condition of average onshore flow in the bottom layer, we observed higher vertical sediment flux during ebb than flood tidal currents. The on-shelf and off-shelf differences in turbulent mixing and water depth mainly cause such difference in sediment flux. We propose to call this export process of particulate matter the tidal pump at the shelf edge.  相似文献   

Baroclinic eddies south of Cheju Island in the East China Sea   总被引：3，自引：0，他引：3  

Tetsuo Yanagi  Takanori Shimizu  Takeshi Matsuno 《Journal of Oceanography》1996,52(6):763-769

The detailed structures of baroclinic eddies, that is, an anticlockwise circulation in the upper layer and a clockwise one in the lower layer south of Cheju Island in the East China Sea have been revealed by intensive field observation. Such baroclinic eddies are accompanied by the southward spreading of the Yellow Sea Bottom Cold Water.  相似文献   

The identification, counting, and measurement of phytoplankton by an image-processing system     

Ishii  T.; Adachi  R.; Omori  M.; Shimizu  U.; Irie  H. 《ICES Journal of Marine Science》1987,43(3):253-260

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Flare event statistics on UV Ceti-type stars     

K. Ishida  Mahasen Aputra  K. Ichimura  Y. Shimizu 《Astrophysics and Space Science》1991,182(2):227-240

A statistical study of 228 flares on the three UV Ceti-type stars, i.e., YZ CMi, AD Leo, and EV Lac, is presented. Observations were gathered by Ichimura and Shimizu over a total monitoring time of 907 hours distributed over 18 years (1971 to 1988). Period analysis of flare activity was performed, and no periodicity was detected on the three stars for either the flare number rate or the energy rate in time-scales ranging from a year up to 14 years. Average colour of flares at peak was (U-B)=–0.98±0.17 and (B-V)=0.05±0.13. Cumulative number distributions of flare event time-integrated energies were solved by a least-squares method on a log-log plot for a power-law function to get both the constant of and the gradient , which were found to be similar among the three stars. The gradient showed that rare large flare events radiate most of the energy released by all the flare events in the monitoring time. The flare number rate and energy rate are similar if the power-law distributions are extended up to a specific maximum energy. In reality, the Kolmogorov-Smirnov test showed that the observed cumulative number distributions of flare event energy were not necessarily a power-law function. The monte-Carlo simulation, however, indicates that the monitoring time and/or the patrol observation time interval may not be long enough to get the average flare number rate and energy rate, especially at the upper energy limits which are statistically unreliable.  相似文献   

Buoyancy-driven perturbations in a rapidly rotating,electrically conducting fluid: part II – dynamo action     

Arnaud Chulliat  Hisayoshi Shimizu  David E. Loper 《地球物理与天体物理流体动力学》2013,107(6):471-487

The helicity, electromotive force and α-effect produced in a homogeneous, rapidly rotating, electrically conducting fluid by an isolated source of buoyancy at small Elsasser number are calculated, visualized and analyzed. Due to physical symmetries of the system, the integrals of helicity and electromotive force over all space are zero. However, each has a significant non-zero value when integrated over the cross section of the Taylor column. The local α-effect is found to be significantly anisotropic; it is strongest when the applied magnetic field is toroidal and the resulting EMF is parallel to the applied field.  相似文献   

Polarization Calibration of the <Emphasis Type="Italic">Chromospheric Lyman-Alpha SpectroPolarimeter</Emphasis> for a 0.1% Polarization Sensitivity in the VUV Range. Part II: In-Flight Calibration     

G. Giono  R. Ishikawa  N. Narukage  R. Kano  Y. Katsukawa  M. Kubo  S. Ishikawa  T. Bando  H. Hara  Y. Suematsu  A. Winebarger  K. Kobayashi  F. Auchère  J. Trujillo Bueno  S. Tsuneta  T. Shimizu  T. Sakao  J. Cirtain  P. Champey  A. Asensio Ramos  J. Štěpán  L. Belluzzi  R. Manso Sainz  B. De Pontieu  K. Ichimoto  M. Carlsson  R. Casini  M. Goto 《Solar physics》2017,292(4):57

The Chromospheric Lyman-Alpha SpectroPolarimeter is a sounding rocket instrument designed to measure for the first time the linear polarization of the hydrogen Lyman-\({\upalpha }\) line (121.6 nm). The instrument was successfully launched on 3 September 2015 and observations were conducted at the solar disc center and close to the limb during the five-minutes flight. In this article, the disc center observations are used to provide an in-flight calibration of the instrument spurious polarization. The derived in-flight spurious polarization is consistent with the spurious polarization levels determined during the pre-flight calibration and a statistical analysis of the polarization fluctuations from solar origin is conducted to ensure a 0.014% precision on the spurious polarization. The combination of the pre-flight and the in-flight polarization calibrations provides a complete picture of the instrument response matrix, and a proper error transfer method is used to confirm the achieved polarization accuracy. As a result, the unprecedented 0.1% polarization accuracy of the instrument in the vacuum ultraviolet is ensured by the polarization calibration.  相似文献   

Surface current and vertical thermal structure on the continental slope in Tosa Bay     

Hiroshi Kuroda  Manabu Shimizu  Yuuichi Hirota  Daisuke Ambe  Hideki Akiyama 《Journal of Oceanography》2008,64(1):81-91

In order to specify a vertical thermal structure related to surface current variation on the continental slope in Tosa Bay, Japan, we analyzed monthly regular hydrographic measurements in the years 1991–2004. Subsurface temperature below 200 m on the slope was found to vary synchronously with the vertical displacement of the main thermocline around 200 m. It is shown that the vertical-averaged temperature below 200 m is significantly correlated with an along-isobath/southwestward surface current velocity on the slope. This correlation indicates that when a strong (weak) southwestward surface current is observed, temperature below 200 m decreases (increases) simultaneously, that is, isotherms below the 200 m are displaced upward (downward) together with the main thermocline. Moreover, when the strong southwestward flow is detected, across-isobath isotherms around 200 m slope upward toward the offshore direction. Furthermore, it is suggested that as the Kuroshio axis moves offshore south of the bay, the southwestward flow tends to be weakened by the combined effect of other Kuroshio parameters such as transport and stream width as well as the Kuroshio axis position. As a result, it is inferred that the correlation between the surface current and subsurface temperature can be interpreted in terms of the formation and decay of an anticlockwise circulation interacting with a cold eddy.  相似文献   

Determination of the oxidation state of radiogenic Pb in natural zircon using X-ray absorption near-edge structure     

Kazuya Tanaka  Yoshio Takahashi  Kenji Horie  Hiroshi Shimizu  Takashi Murakami 《Physics and Chemistry of Minerals》2010,37(4):249-254

We examined the L_III-edge Pb X-ray absorption near-edge structure (XANES) of three natural zircon samples with different amounts of radiation doses (1.9 × 10¹⁵ to 6.8 × 10¹⁵ α-decay events/mg). The results suggest that the oxidation state of radiogenic Pb in the zircon sample with the highest radiation dose is divalent. The XANES spectra of the two other samples with lower radiation doses suggest that radiogenic Pb(II) is present, and further that some Pb may be tetravalent. This is the first work on the determination of the oxidation state of radiogenic Pb in natural zircon using XANES.  相似文献   

Mineralogical and geochemical characteristics of hydrothermal alteration of basalt in the Kuroko mine area, Japan: implications for the evolution of a Back Arc Basin hydrothermal system     

Naotatsu Shikazono  Minoru Utada  Masaaki Shimizu 《Applied Geochemistry》1995,10(6)

Basalt in the Furutobe District of the Kuroko mine area in Japan is characterized by abundant chlorite and epidote. Fluid inclusion studies indicate that chlorite is formed at lower temperatures (230–250°C) than epidote (250–280°C). The seawater/basalt mass ratio for the early chlorite-rich alteration was high (max. 40), but that for the later alteration was low (0.1–1.8). The CaO, Na₂O and SiO₂ of the bulk rock correlate negatively with MgO, while FeO and Σ Fe correlate positively with MgO. These changes in the characteristic features of hydrothermal alteration from early to late are generally similar to those for a mid-ocean ridge geothermal system accompanying basalt alteration.The MgO/FeO ratios of chlorite and actinolite and the Fe₂O₃ concentration of epidote from the basalt are greater than those of mid-ocean ridge basalt probably owing to the differences in the Fe₂O₃/FeO and MgO/FeO ratios of the parent rocks. The lower CaO concentration and the higher Na₂O concentration of the bulk rock compared with altered mid-ocean ridge basalt can be interpreted in terms of the difference in original bulk rock compositions.The Furutobe basalt, as well as other submarine back arc basalts, contains more vesicles filled with hydrothermal minerals (epidote, calcite, quartz, chlorite, pyrite) than do the mid-ocean ridge basalts. The abundance of vesicles plays an important role in controlling the secondary mineralogy and geochemistry of hydrothermally altered submarine back arc basin basalts.  相似文献