Development of a 2-km resolution ocean model covering the coastal seas around Japan for operational application     

Sakamoto  Kei  Tsujino  Hiroyuki  Nakano  Hideyuki  Urakawa  Shogo  Toyoda  Takahiro  Hirose  Nariaki  Usui  Norihisa  Yamanaka  Goro 《Ocean Dynamics》2019,69(10):1181-1202

Ocean Dynamics - In order to expand the coastal ocean monitoring and forecasting system of the Japan Meteorological Agency from the Seto Inland Sea to the entire coastal seas of Japan, a 2-km...  相似文献   

Numerical analysis on seismic response of Shinkansen bridge-train interaction system under moderate earthquakes     

Mitsuo Kawatani  Toshiro Hayashikawa  Takashi Matsumoto 《地震工程与工程振动(英文版)》2011,10(1):85-97

This study is intended to evaluate the influence of dynamic bridge-train interaction (BTI) on the seismic response of the Shinkansen system in Japan under moderate earthquakes. An analytical approach to simulate the seismic response of the BTI system is developed. In this approach, the behavior of the bridge structure is assumed to be within the elastic range under moderate ground motions. A bullet train car model idealized as a sprung-mass system is established. The viaduct is modeled with 3D finite elements. The BTI analysis algorithm is verified by comparing the analytical and experimental results. The seismic analysis is validated through comparison with a general program. Then, the seismic responses of the BTI system are simulated and evaluated. Some useful conclusions are drawn, indicating the importance of a proper consideration of the dynamic BTI in seismic design.  相似文献   

Phytoplankton productivity in the western subarctic gyre of the North Pacific in early summer 2006     

Tetsuichi Fujiki  Kazuhiko Matsumoto  Shuichi Watanabe  Takuji Hosaka  Toshiro Saino 《Journal of Oceanography》2011,67(3):295-303

We deployed a profiling buoy system incorporating a fast repetition rate fluorometer in the western subarctic Pacific and carried out time-series observations of phytoplankton productivity from 9 June to 15 July 2006. The chlorophyll a (Chl a) biomass integrated over the euphotic layer was as high as 45–50 mg Chl a m⁻² in the middle of June and remained in the 30–40 mg Chl a m⁻² range during the rest of observation period; day-to-day variation in Chl a biomass was relatively small. The daily net primary productivity integrated over the euphotic layer ranged from 144 to 919 mg C m⁻² day⁻¹ and varied greatly, depending more on insolation rather than Chl a biomass. In addition, we found that part of primary production was exported to a 150-m depth within 2 days, indicating that the variations in primary productivity quickly influenced the organic carbon flux from the upper ocean. Our results suggest that the short-term variability in primary productivity is one of the key factors controlling the carbon cycle in the surface ocean in the western subarctic Pacific.  相似文献   

Physical determinants of intertidal communities on dissipative beaches: Implications of sea-level rise     

Tsuyuko Yamanaka  Dave RaffaelliPiran C.L. White 《Estuarine, Coastal and Shelf Science》2010

Sea-level rise is likely to cause significant changes in the morphodynamic state of beaches in the higher latitudes, resulting in steeper beaches with larger particle sizes. These physical changes have implications for beach invertebrate communities, which are determined largely by sediment particle size, and hence for ecosystem function. Previous studies have explored the relationships between invertebrate communities and environmental variables such as particle size, beach slope and exposure to wave action, and often these physical variables can be integrated in various indices of morphodynamic state. Most of these studies incorporated a full range of beach types that included wave-dominated surf beaches, where the wave action is harsh enough to enable reliable estimates of breaker height, a parameter included in several of the indices, and concluded that more dissipative beaches with gentler slopes and finer particle sizes often support a higher number of species and greater abundance than more reflective beaches. Whether these predictions remain valid for less wave-dominated beaches, where breaker height is more difficult to determine, is uncertain. In the present study, the abundance of meio- and macrofauna was quantified across a range of beaches in the UK, which are generally towards the lower energy end of the morphodynamic gradient, and their relationships with beach physical properties explored. No significant relationships were found between abundance and the standard morphodynamic indices, but significant relationships were found for both macro- and meiofaunal abundance when these indices were combined with an exposure index (derived from velocity, direction, duration and the effective fetch). All the relationships identified between abundance and combined morphodynamic indices indicated a higher abundance of both macro- and meiofauna on the more dissipative beaches. The reverse was however found for species richness. If predictions that accelerated sea-level rise will move beaches towards a more reflective morphodynamic state are correct, this could lead to declines in the abundance of meio- and macrofauna, with potential adverse consequences for ecosystem functioning.  相似文献   

Effects of bottom bracings on torsional dynamic characteristics of horizontally curved twin I-girder bridges with different curvatures   总被引：1，自引：0，他引：1  

Robiul Awall  Toshiro Hayashikawa  Takashi Matsumoto 《地震工程与工程振动(英文版)》2012,11(2):149-162

Curved twin I-girder bridges (CTIGBs) have low torsional stiffness that makes them vulnerable to dynamic loads.This study investigates the effects of bottom bracings on the torsional dynamic characteri...  相似文献   

Exploration of deep sedimentary layers in Tacna city,southern Peru,using microtremors and earthquake data for estimation of local amplification   总被引：1，自引：1，他引：0  

Hiroaki Yamanaka  Mileyvi Selene Quispe Gamero  Kosuke Chimoto  Kouichiro Saguchi  Diana Calderon  Fernándo Lázares La Rosa  Zenón Aguilar Bardales 《Journal of Seismology》2016,20(1):107-116

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Net Zooplankton and the biological pump off Sanriku, Japan     

Satoru Taguchi  Toshiro Saino 《Journal of Oceanography》1998,54(5):573-582

Taxonomic composition, size composition, standing stock, and chemical composition of mesozooplankton were determined to examine the contribution of their fecal pellets to the vertical flux of organic carbon at the outside, the edge, and the center of the warm core ring. The warm core ring significantly affects not only their taxonomic composition and size composition but also their standing stock and chemical composition. The zooplankton at the center of the warm core ring was characterized by the absence of carnivores at the top of the size-trophic relation and filter feeding planktonic tunicates at the bottom. Zooplankton carbon biomass at the outside of the ring was one-third less than that at the center of the ring. The vertical flux of fecal pellets obtained from the pellet volume (12.3 mgC m⁻²d⁻¹) contributed 19 to 96% of the flux (13 to 64 mgC m⁻² d⁻¹) estimated from the body carbon and the fecal pellet production rate. The estimated flux of fecal pellets was 6 to 27% of vertical carbon flux (236 mgC m⁻²d⁻¹) determined by the sediment traps. Microscopic determination of fecal pellets and plankton in the sediment trap samples indicated high grazing activity during the sinking process. Those observations might suggest that particles other than fecal pellets contributed significantly to the vertical carbon flux and fecal pellets were settled directly without loss or being recycled within the surface mixed layer.  相似文献   

Satellite and ship observations of Kuroshio warm-core ring 93A off Sanriku, northwestern North Pacific, in spring 1997     

Sei-Ichi Saitoh  Denzo Inagake  Kousei Sasaoka  Joji Ishizaka  Yukihiro Nakame  Toshiro Saino 《Journal of Oceanography》1998,54(5):495-508

Synoptic ship and satellite observations were performed of the Kuroshio warm-core ring (KWCR) 93A and its adjacent waters, off Sanriku, northwestern North Pacific, between early April and late June 1997. The temporal and spatial distribution of chlorophylla (Chl-a) and sea surface temperature in the study area were analyzed using data from ADEOS Ocean Color and Temperature Scanner (OCTS) and NOAA Advanced Very High Resolution Radiometer (AVHRR). The objective of this study was to describe the temporal and spatial variability of the spring bloom and understand its relationship with the changes in the hydrographic structure of these waters in and around KWCR 93A. The maximum value of Chl-a concentration in the ring was less than 1 mg/m³ during April. The spring bloom in the ring occurred early in May and the relatively high maximum (>1.0 mg/m³) continued from early in May to mid-June. In late June, a ship-observed surface Chl-a concentration of less than 0.4 mg/m³ suggests that the spring bloom had already declined in and around KWCR 93A. Double spiral structures of warm and cold streamers appeared from late April to mid-May, which may have an influence on the occurrence of the spring bloom in and around the ring. In this episodic event, the warm streamer can maintain the available potential energy of the ring and the strength of upwelling around the ring. The cold streamer provided water with a high Chl-a concentration to the surface layer of the ring. In order to understand the temporal and spatial variability of Chl-a distribution in the ring, the behavior of the warm and cold streamers needs to be taken into consideration.  相似文献   

Regional 3-D heterogeneities by waveform inversion – application to the Atlantic area     

Satoru Honda  Toshiro Tanimoto 《Geophysical Journal International》1987,91(3):737-753

The waveform inversion method described in Woodhouse & Dziewonski (1984) was modified to retrieve regional scale 3-D heterogeneities by using the minor arc part of seismograms. The lateral heterogeneities are expanded horizontally into blocks (10°× 10°) and radially into Legendre polynomials up to order 3 (0–670 km), and thus the results show much fine details of lateral variation than previous global scale studies. We assumed that the heterogeneities produce the perturbation of eigenfrequencies which are the minor arc average of local eigenfrequency shift. We applied the method to the upper mantle beneath the Atlantic Ocean and its environments. Care was taken about the weighting of the data set. We found that the fit of each seismogram became better when the weighting of each seismogram is proportional to the inverse of initial data residuals. Resolution is good in the triangular region surrounded by South America, Europe, and North America. Resolution is not good in the South Atlantic because of the poor path coverage. Depth resolution is not clear, because of the use of Legendre polynomials, though the results suggest a broad half-width of the order of 200 km or more. We found some similarities between previous global studies and our results. For example, low velocities beneath the East Pacific Rise, Chile Rise and Azores triple junction and a high velocity Canadian shield are obtained. However, there are also differences; the high-velocity zone beneath the Brazilian shield at shallow depth is not a prominent feature in this study. Instead, we found a somewhat unexpected feature near the Romanche and Vema fracture zones where shallow positive anomalies exist. Smoothed results calculated by the spherical harmonic expansion are also shown for the purpose of comparison with global studies.  相似文献   

Short term variability of Particle fluxes and its relation to variability in sea surface temperature and chlorophylla field detected by Ocean Color and Temperature Scanner (OCTS) off Sanriku, northwestern North Pacific in the spring of 1997     

Toshiro Saino  Shaoling Shang  Yoshihisa Mino  Koji Suzuki  Hideaki Nomura  Sei-ichi Saitoh  Hideo Miyake  Toshiyuki Masuzawa  Koh Harada 《Journal of Oceanography》1998,54(5):583-592

A sediment trap experiment was carried out in conjunction with an over flight of Ocean Color Temperature Scanner (OCTS) on board Advanced Earth Observing Satellite (ADEOS) at 40°N, 143°E off Sanriku in April to May 1997. Short term variability of particle fluxes was examined at depths of 450 m and 600 m from April 6 to May 1 with a sampling interval of two days, and at 450 m with one day interval from 2nd to 10th May. Daily averaged mass flux at 450 m and 600 m was 815 mg m⁻²d⁻¹ and 862 mg m⁻²d⁻¹, respectively. A sharp increase in mass flux was observed during the period from April 26 to April 29 with the highest mass flux of 8 g m⁻²d⁻¹. About 85% of the total mass flux for the entire duration (26 days) was collected within these 4 days. Trapped material during the peak flux period was mainly composed of diatoms dominated byThalassiosira spp. and resting spores ofChaetoceros spp. This suggested that the peak flux was the result of (a) diatom bloom(s) in the euphotic column. Current meter records at 420 m showed that on April 26 and 27, the period when the peak flux was observed, the southwestward current had diminished in strength and changed its direction northwestward. Low current speeds appeared to have enhanced trap efficiency to help form the peak flux. A time series of OCTS Intensive-LAC (Local Area Coverage: Region B) images from mid-March to early May was examined todetect phytoplankton bloom(s). In the March 26th Chl image, high concentration region was restricted to the southwest off Cape Erimo, but spread around the warm core ring (WCR) 93A by April 10. East of the WCR93A, high Chl concentration remained steady until May, but to the west of the WCR93A, Chl decreased rapidly before the 19th of April. From this observation we suspect that the peak flux observed at the end of April originated from a bloom, which ceased on the 17th or 18th of April, in the region north of 40°N and west of 143°E. Taking the current meter records into account, the source region for the trapped material is most likely around southwest of the Cape Erimo.  相似文献