ASCA Observations of X-ray Emission from Ultra-luminous Infrared Galaxies     

Takao Nakagawa  Tsuneo Kii  Ryuichi Fujimoto  Toshiyuki Miyazaki  Hajime Inoue  Yasushi Ogasaka  Ryohei Kawabe 《Astrophysics and Space Science》1999,266(1-2):43-48

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A Late Holocene geomagnetic secular variation record from Erhai Lake, southwest China   总被引：1，自引：0，他引：1  

Masayuki Hyodo  Arata Yoshihara  Kenji Kashiwaya  Takashi Okimura  Toshiyuki Masuzawa  Ryotaro Nomura  Shingo Tanaka  Tang Bang Xing  Liu Su Qing  & Liu Shi Jian 《Geophysical Journal International》1999,136(3):784-790

A secular variation record of the geomagnetic field direction for the last 6.5  kyr has been obtained from the magnetization of sediment cores from Erhai Lake, southwest China. In order to make a comparison with this record, secular variation in east-central China was investigated by combining available magnetic field data from historical records and archaeomagnetic measurements since about 350 bc . The secular variation in Erhai Lake shows features consistent with the combined record, except for the oldest three observed declination swings in Sian from 720 to 900 ad . Many features of declination and inclination in China also occur in Japan. From 500 to 1000 ad , declination was westerly ranging from about −20° to −5° in Erhai Lake, east-central China, and Japan.  相似文献   

Estimation of canopy drying time after rainfall using sap flow measurements in an emergent tree in a lowland mixed‐dipterocarp forest in Sarawak,Malaysia     

Tomonori Kume  Koichiro Kuraji  Natsuko Yoshifuji  Toshiyuki Morooka  Shinji Sawano  Lucy Chong  Masakazu Suzuki 《水文研究》2006,20(3):565-578

This study emphasizes the importance of canopy drying time (CDT) after rainfall in a lowland tropical rain forest. In this study, we estimate CDT using sap flow velocities measured by a heat‐pulse method in an emergent tree in a lowland mixed‐dipterocarp forest. Estimated CDT (ECDT) for each rain event has been defined as the time from rainfall cessation to the specific time derived from the difference between diurnal courses of sap flow velocities on a rainy day versus bright days. ECDT could be derived for 22 rain events that were grouped into two types, depending on whether rainfall ceased before or after noon. The ECDTs were distributed more widely and with greater values when rainfall ceased before noon (Type 1) than after noon (Type 2). The ECDTs of both Type 1 and Type 2 decreased with increases in net radiation (Rn) and vapour pressure deficit (VPD) after rainfall. This result shows that ECDT is determined mainly by post‐rainfall evaporation rates. The sap flow velocity as a detector of canopy wetness worked out well because of the specific rainfall characteristics at this site. The practical limitations of the method using sap flow velocities are discussed in relation to rainfall characteristics and time lags between transpirations and sap flow velocities. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Step-like structure in temperature and salinity profiles,observed near icebergs trapped by fast ice,Antarctica     

Kay I. Ohshima  Toshiyuki Kawamura  Takatoshi Takizawa  Shuki Ushio 《Journal of Oceanography》1994,50(3):365-372

Step-like thermohaline structure was observed near icebergs trapped by fast ice in Lützow-Holm Bay, Antarctica. The structure was developed within the draft depth of the icebergs. The typical vertical distance between the succeeding step surfaces is 20–30 m, and the temperature and salinity differences across the step surface are about 0.05–0.06 deg and 0.06–0.10 psu, respectively. The structure appears to be generated by a sea-water/iceberg interaction, and is explainable by a simple model in which an ice wall is placed in the ocean linearly stratified by vertical salinity gradient.  相似文献   

Tidal exchange through Naruto,Akashi and Kitan Straits     

Norihisa Imasato  Toshiyuki Awaji  Hideaki Kunishi 《Journal of Oceanography》1980,36(3):151-162

In order to re-evaluate the water volume exchange through Naruto Strait, we have performed a numerical experiment (nonlinear barotropic model including the actual depth of water and the details of shoreline) where trajectories of a number of labeled particles are calculated during a full cycle of the M₂ tidal current. The ratio of water volume exchanged through Naruto Strait to that through Akashi Strait is found to be twice as large as the previously estimated value. The calculated water exchange rate is 104 % for Naruto Strait, 52 % for Akashi Strait and 28 % for Kitan Strait. In the case where the tide-induced residual current is excluded from the calculated velocity field (i.e. considering only the M₂ current), the calculated exchange rate maintains the level of 68 % for Naruto Strait, 18 % for Akashi Strait and 11 % for Kitan Strait, respectively. The mechanism of tidal exchange through these three straits is discussed, and it is shown that a suitable exchange rate is obtained by starting the calculation of trajectories of labeled particles at the time of either a maximum ebb- or flood-current.  相似文献   

Estimates of Energy Dissipation Rates in the Three-Dimensional Deep Ocean Internal Wave Field   总被引：2，自引：0，他引：2  

Watanabe  Michio  Hibiya  Toshiyuki 《Journal of Oceanography》2005,61(1):123-127

Using the “Eikonal Approach” (Henyey et al., 1986), we estimate energy dissipation rates in the three-dimensional Garrett-Munk internal wave field. The total energy dissipation rate within the undisturbed GM internal wave field is found to be 4.34 × 10⁻⁹ W kg⁻¹. This corresponds to a diapycnal diffusivity of about 0.3 × 10⁻⁴ m²s⁻¹, which is less than the value 10⁻⁴ m²s⁻¹ required to sustain the global ocean overturning circulation. Only when the high vertical wavenumber, near-inertial current shear is enhanced can diapycnal diffusivity reach ∼10⁻⁴ m²s⁻¹. It follows that the energy supplied at low vertical wavenumbers and low frequencies is efficiently transferred to high vertical wavenumbers and near-inertial frequencies in the mixing hotspots in the real ocean.  相似文献   

A dispersion equation and dispersion coefficient for material transport in Inland Seas     

Toshiyuki Awaji  Hideaki Kunishi 《Journal of Oceanography》1983,39(1):1-8

To analyse material transport in inland seas, a horizontal two-dimensional dispersion equation is derived, and the dispersion coefficient due to the combined effect of vertical turbulent mixing and vertical shear of both a steady current and a tidal current is studied. In the present study, the assumption that velocity is uniform in horizontal planes is not necessary, and velocity has a free vertical profile; thus the dispersion coefficient formulated is general, and is represented by a tensor of the second order. The properties of the dispersion coefficient in the horizontal two-dimensional dispersion model are also investigated, and it is shown that the time-averaged dispersion coefficient due to the tidal current over a tidal period is approximately half that due to the steady current, if the velocity amplitude and the vertical profile of the tidal current are the same as those of the steady current (a similar result was presented byBowden (1965) for horizontal one-dimensional models). Finally, the dispersion coefficient in Hiuchi-Nada (Hiuchi Sound) in the central part of the Seto Inland Sea is evaluated by using the model. The values of the dispersion coefficient in that region range from 10³ cm² s^–1 to 10⁵ cm² s^–1 when vertical turbulent diffusivity is taken to be 50 cm² s^–1.  相似文献   

Numerical Study of the Generation and Propagation of Trigger Meanders of the Kuroshio South of Japan     

Takahiro Endoh  Toshiyuki Hibiya 《Journal of Oceanography》2000,56(4):409-418

We examine the processes underlying the generation and propagation of the small meander of the Kuroshio south of Japan which occurs prior to the transition from the non-large meander path to the large meander path. The study proceeds numerically by using a two-layer, flat-bottom, quasi-geostrophic inflow-outflow model which takes account of the coastal geometries of Kyushu, Nansei Islands, part of the East China Sea, and the Izu Ridge. The model successfully reproduces the observed generation and propagation features of what is called "trigger meander" until it passes by Cape Shiono-misaki; presumably because of the absence of the bottom topography, the applicability of the present numerical model becomes questionable after the trigger meander passes by Cape Shiono-misaki. The generation of the trigger meander off the south-eastern coast of Kyushu is shown to be associated with the increase in the supply of cyclonic vorticity by the enhanced current velocity in the upper layer along the southern coast of Kyushu where the no-slip boundary condition is employed. Thereafter, the trigger meander propagates eastward while inducing an anticyclone-cyclone-cyclone pair in the lower layer. The lower-layer cyclone induced in this way, in particular, plays a crucial role in intensifying the trigger meander trough via cross-stream advection in the upper layer; the intensified trigger meander trough then further amplifies the lower-layer cyclone. This joint evolution of the upper-layer meander trough and the lower-layer cyclone indicates that baroclinic instability is the dominant mechanism underlying the rapid amplification of the eastward propagating trigger meander.  相似文献   

Unconformity between a Late Miocene–Pliocene accretionary prism (Nishizaki Formation) and Pliocene trench‐slope sediments (Kagamigaura Formation), central Japan     

Yuzuru Yamamoto  Shun Chiyonobu  Toshiyuki Kurihara  Asuka Yamaguchi  Shoko Hina  Mari Hamahashi  Hugues Raimbourg  Romain Augier  Leslie Gadenne 《Island Arc》2012,21(4):231-234

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Effects of high CO2 seawater on the copepod (Acartia tsuensis) through all life stages and subsequent generations     

Kurihara H  Ishimatsu A 《Marine pollution bulletin》2008,56(6):1086-1090

We studied the effects of exposure to seawater equilibrated with CO(2)-enriched air (CO(2) 2380 ppm) from eggs to maturity and over two subsequent generations on the copepod Acartia tsuensis. Compared to the control (CO(2) 380 ppm), high CO(2) exposure through all life stages of the 1st generation copepods did not significantly affect survival, body size or developmental speed. Egg production and hatching rates were also not significantly different between the initial generation of females exposed to high CO(2) and the 1st and 2nd generation females developed from eggs to maturity in high CO(2). Thus, the copepods appear more tolerant to increased CO(2) than other marine organisms previously investigated for CO(2) tolerance (i.e., sea urchins and bivalves). However, the crucial importance of copepods in marine ecosystems requires thorough evaluation of the overall impacts of marine environmental changes predicted to occur with increased CO(2) concentrations, i.e., increased temperature, enhanced UV irradiation, and changes in the community structure and nutritional value of phytoplankton.  相似文献