Wave trains over the sea due to sea breezes     

Osamu Chiba  G. Naito  F. Kobayashi  H. Toritani 《Boundary-Layer Meteorology》1994,70(4):329-340

Meteorological observation by a helicopter was carried out to investigate the structure of sea breezes over the coastal area of Tosa Bay in Shikoku island, Japan. Several groups of wave trains were found over the sea during a flight made on 25 November 1992. Not only the terrain barrier but the remaining cold air pools formed in valleys hindered further advance of the sea breeze inland, so that the presence of such wave trains may appear to be due to the effect of the secondary flow which supplies moister and cooler air from behind the sea breeze front.  相似文献   

A fault scarp in an urban area identified by LiDAR survey: A Case study on the Itoigawa–Shizuoka Tectonic Line, central Japan   总被引：2，自引：2，他引：0  

H. Kondo  S. Toda  K. Okumura  K. Takada  T. Chiba 《Geomorphology》2008,101(4):731-739

A light detection and ranging (LiDAR) survey was conducted in a densely built-up area to generate a high-resolution digital elevation model (DEM) to look for active faults. The urban district of Matsumoto City in central Japan is located in a 3-km² basin along the Itoigawa–Shizuoka Tectonic Line active fault system, one of Japanese onshore fault systems with the highest earthquake probability. A high-resolution DEM at a 0.5-m-grid interval was obtained after removing the effects of laser returns from buildings, clouds and vegetation. It revealed a continuous scarp, up to ~ 2 m in height. Borehole data and archaeological studies indicate the scarp was formed during the most recent faulting event associated with historical earthquakes. In addition, the fault scarp strongly supports that the urban district is in a pull-apart basin related to a fault step-over between two left-lateral strike-slip faults. Consequently, accurate interpretation of fault geometry is crucial to provide estimates of future surface deformation and to allow modeling of basin structure and strong ground motion. Thus, the LiDAR mapping survey in urban districts is effective for detailed active fault mapping in order to constrain basin structure and to forecast the exact location of surface rupturing associated with large earthquakes.  相似文献   

Risk assessment of water inrush in karst tunnels based on two-class fuzzy comprehensive evaluation method     

Handong Chu  Guangli Xu  Noriyuki Yasufuku  Zhang Yu  Pola Liu  Jifeng Wang 《Arabian Journal of Geosciences》2017,10(7):179

A feasible and accurate method named two-class fuzzy comprehensive evaluation is put forward to assess the risk of water inrush in karst tunnels. In view of regarding tunnel face as the evaluation object, 12 influencing factors of water inrush are selected as the evaluation index system consisting of 4 first-class and 12 second-class indices. Based on fuzzy mathematics theory and expert evaluation method, all the indices are quantitatively graded according to five risk grades. The weights of indices affecting water inrush are rationally distributed by using analytic hierarchy process. Membership functions and weights of indices are utilized to stepwise compute the membership degree of indices corresponding to risk grade, and the principle of maximum membership degree is carried out to discern the risk grade of water inrush. The tunnel faces in seven segments of Qiyueshan tunnel are chosen as the case studies. Evaluation results are derived from the proposed method, and they are generally consistent with the actual results through comparisons. This method provides a cogent way for evaluating the risk of water inrush in karst tunnels.  相似文献   

Non-food-chain transfer of sediment-associated persistent organic pollutants to a marine benthic fish     

Takeo Sakurai  Jun Kobayashi  Yoshitaka Imaizumi  Noriyuki Suzuki 《Marine pollution bulletin》2009,58(7):1072-1077

We investigated the transfer of persistent organic pollutants (POPs) from unspiked bottom sediment to a benthic marine fish, marbled sole (Pleuronectes yokohamae), via non-food-chain pathways, i.e., via sediment particles and water column. One-year-old sole were held for 28 days in an exposure tank with bottom sediment or in a control tank. o,p′-DDE and tri- to penta-chlorobiphenyls were transferred from the sediment to the fish via non-food-chain pathways, as demonstrated by concentrations in the exposed fish at 2.5-30 times the control levels. A model analysis based on first-order kinetic equations indicated that the overall rate constant of transfer of these compounds from sediment to fish was generally lower than that from food (median of ratio, 0.48). It also suggested that relatively high concentrations of the other POPs in the food and the longer times necessary for them to reach a steady state masked any transfer of them from the sediment.  相似文献   

The use of a water mass curtain to control fish behavior for marine ranching     

Chokei Itosu  Makoto Nakamura  Yuichi Chiba  Shinya Otake 《Ocean Engineering》1998,25(4-5)

A practical method is described of initiating a water mass curtain (a jet flow of water partitioning another body of water) to be used to control fish movements, along with its theoretical analysis. In this paper, equations to evaluate the change of density and upward flow rates in a water curtain due to entrainment are presented, and the accuracy of the equations is verified experimentally. The discontinuity of the density on the boundary between jet and ambient fluid was assumed in the analysis, since our experiments showed that the instantaneous density distribution was discontinuous. The equations are much simpler than the conventional formulae deduced by assuming a Gaussian curve, and are amenable to practical usage. The control efficiency of the water curtain is very good for young red sea bream.  相似文献   

Origin of the Tonaru body in the Sanbagawa metamorphic belt,SW Japan     

Shogo Aoki  Kazumasa Aoki  Kentaro Chiba  Shuhei Sakata  Yuta Tsuchiya  Daichi Kato 《Island Arc》2020,29(1)

Zircon U–Pb dating of the Tonaru metagabbro body in the Sanbagawa metamorphic belt, southwest Japan, suggests that igneous events at ca 200–180 Ma were involved in the protolith formation. The trace element compositions of the Tonaru zircons are enriched in U (a fluid‐mobile element) and Sc (an amphibole‐buffered element), and depleted in Nb (a fluid‐immobile element), suggesting that the parental magmas related to the Tonaru metagabbros formed in an arc setting. Integration of our results with previous studies of the metasedimentary rocks in the Tonaru body clearly indicates that the protoliths of the Tonaru body were produced by oceanic‐arc magmatism. With the previous geochronological and geological studies, the tectono‐magmatic–metamorphic history of the Tonaru and other mafic bodies in the Sanbagawa metamorphic belt may be summarized as follows: (i) the protolith formation by the oceanic‐arc magmatic event had occurred at 200–180 Ma; (ii) the protoliths were accreted in the trench at ca 130–120 Ma; and (iii) they were completely subducted into the depth of the eclogite‐facies condition after 120 Ma.  相似文献   

A near-infrared survey of Miras and the distance to the Galactic Centre     

Noriyuki Matsunaga †  Takahiro Kawadu  Shogo Nishiyama †  Takahiro Nagayama  Hirofumi Hatano †  Motohide Tamura  Ian S. Glass  Tetsuya Nagata 《Monthly notices of the Royal Astronomical Society》2009,399(4):1709-1729

We report the results of a near-infrared survey for long-period variables in a field of view of 20× 30 arcmin² towards the Galactic Centre (GC). We have detected 1364 variables, of which 348 are identified with those reported in Glass et al. We present a catalogue and photometric measurements for the detected variables and discuss their nature. We also establish a method for the simultaneous estimation of distances and extinctions using the period–luminosity relations for the JHK _s bands. Our method is applicable to Miras with periods in the range 100–350 d and mean magnitudes available in two or more filter bands. While J band means are often unavailable for our objects because of the large extinction, we estimated distances and extinctions for 143 Miras whose H - and   K _s  -band mean magnitudes are obtained. We find that most are located at the same distance to within our accuracy. Assuming that the barycentre of these Miras corresponds to the GC, we estimate its distance modulus to be  14.58 ± 0.02 (stat.) ± 0.11 (syst.) mag  , corresponding to  8.24 ± 0.08 (stat.) ± 0.42 (syst.) kpc  . We have assumed the distance modulus to the Large Magellanic Cloud to be 18.45 mag, and the uncertainty in this quantity is included in the above systematic error. We also discuss the large and highly variable extinction. Its value ranges from 1.5 mag to larger than 4 mag in     except towards the thicker dark nebulae and it varies in a complicated way with the line of sight. We have identified mid-infrared counterparts in the Spitzer /IRAC catalogue of Ramírez et al. for most of our variables and find that they follow rather narrow period–luminosity relations in the 3.6–8.0 μm wavelength range.  相似文献   

Determining the equation of state of the expanding Universe: inverse problem in cosmology     

Takashi Nakamura  Takeshi Chiba 《Monthly notices of the Royal Astronomical Society》1999,306(3):696-700

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Distribution of heterotrophic nanoflagellates and their importance as the bacterial consumer in a eutrophic coastal seawater   总被引：4，自引：0，他引：4  

Kimio Fukami  Noriyuki Murata  Yuuki Morio  Toshitaka Nishijima 《Journal of Oceanography》1996,52(4):399-407

Seasonal and vertical changes in abundances of bacteria and heterotrophic nanoflagellates (HNF), and HNF grazing on bacteria were investigated in a small eutrophic inlet of Uranouchi-Wan throughout the years. Bacterial densities in the surface water ranged from 1.2 to 11 (average 4.3)×10⁶ cells ml^–1 with a couple of maxima following the algal blooming. Densities of HNF ranged from 0.54 to 73 (average 16.4)×10³ cells ml^–1 in the surface, and showed almost similar fluctuation pattern to that of bacteria with a time lag of about 1 to 2 weeks. Grazing rates of HNF on bacteria obtained by FLB method were 4.78 to 16.9 (average 10.3±SD 4.8) cells HNF^–1h^–1 in the surface layer in summer, and consequent total bacterial consumption rates by HNF fluctuated from 4 to 99×10⁴ cells ml^–1h^–1. In deeper layers, however, as HNF densities and grazing rates on bacteria were low, the grazing pressure of HNF on bacteria was small. Turnover times of bacteria by HNF grazing in the surface layer were calculated as relatively constant values of 40 to 60 h, however, it decreased to as low as 6 to 7 h when the HNF activity was highest. These results indicate that bacteria grew so actively by consuming organic matter in seawater as to compensate high HNF grazing pressure, and that bacteria and HNF in the microbial loop play important roles on the turnover of substrates in coastal ecosystems.  相似文献   

Decadal-Scale Climate and Ecosystem Interactions in the North Pacific Ocean   总被引：7，自引：0，他引：7  

Arthur J. Miller  Fei Chai  Sanae Chiba  John R. Moisan  Douglas J. Neilson 《Journal of Oceanography》2004,60(1):163-188

Decadal-scale climate variations in the Pacific Ocean wield a strong influence on the oceanic ecosystem. Two dominant patterns of large-scale SST variability and one dominant pattern of large-scale thermocline variability can be explained as a forced oceanic response to large-scale changes in the Aleutian Low. The physical mechanisms that generate this decadal variability are still unclear, but stochastic atmospheric forcing of the ocean combined with atmospheric teleconnections from the tropics to the midlatitudes and some weak ocean-atmosphere feedbacks processes are the most plausible explanation. These observed physical variations organize the oceanic ecosystem response through large-scale basin-wide forcings that exert distinct local influences through many different processes. The regional ecosystem impacts of these local processes are discussed for the Tropical Pacific, the Central North Pacific, the Kuroshio-Oyashio Extension, the Bering Sea, the Gulf of Alaska, and the California Current System regions in the context of the observed decadal climate variability. The physical ocean-atmosphere system and the oceanic ecosystem interact through many different processes. These include physical forcing of the ecosystem by changes in solar fluxes, ocean temperature, horizontal current advection, vertical mixing and upwelling, freshwater fluxes, and sea ice. These also include oceanic ecosystem forcing of the climate by attenuation of solar energy by phytoplankton absorption and atmospheric aerosol production by phytoplankton DMS fluxes. A more complete understanding of the complicated feedback processes controlling decadal variability, ocean ecosystems, and biogeochemical cycling requires a concerted and organized long-term observational and modeling effort. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献