Storm surge simulation using wind-wave-surge coupling model

Simulation of a storm surge caused by Typhoon 9918 in the Yatsushiro Sea, Kyushu, Japan was hindcasted by the synchronous coupled wind-wave-surge model composed of a Meso-scale meteorological model (MM5) for the wind and sea surface pressure, a spectral third-generation wind-wave model (Wavewatch III) for waves, and the coastal ocean model (Princeton Ocean Model). Inclusion of the whitecap wave breaking stresses (whitecap dissipation stress) in the coastal ocean model made it possible to reproduce the extreme surge height in the extremely shallow bay.     

Fault configuration produced by initial arc rifting in the Parece Vela Basin as deduced from seismic reflection data

Abstract   The Parece Vela Basin (PVB), which is a currently inactive back-arc basin of the Philippine Sea Plate, was formed by separation between the Izu-Ogasawara Arc (IOA) and the Kyushu-Palau Ridge (KPR). Elucidating the marks of the past back-arc opening and rifting is important for investigation of its crustal structure. To image its fault configurations and crustal deformation, pre-stack depth migration to multichannel seismic reflection was applied and data obtained by the Japan Agency for Marine-Earth Science and Technology and Metal Mining Agency of Japan and Japan National Oil Corporation (Japan Oil, Gas and Metals National Corporation). Salient results for the pre-stack depth-migrated sections are: (i) deep reflectors exist around the eastern margin of KPR and at the western margin of IOA down to 8 km depth; and (ii) normal fault zones distributed at the eastern margin of the KPR (Fault zone A) and the western margin of the IOA (Fault zone B) have a total displacement of greater than 500 m associated with synrift sediments. Additional normal faults (Fault zone C) exist 20 km east of the Fault zone B. They are covered with sediment, which indicates deposition of recent volcanic products in the IOA. According to those results: (i) the fault displacement of more than 500 m with respect to initial rifting was approximately asymmetric at 25 Ma based on PSDM profiles; and (ii) the faults had reactivated after 23 Ma, based on the age of deformed sediments obtained from past ocean drillings. The age of the base sediments corresponds to those of spreading and rotation after rifting in the PVB. Fault zone C is covered with thick and not deformed volcanogenic sediments from the IOA, which suggests that the fault is inactive.     

Occurrence of juvenile Japanese flounder Paralichthys olivaceus in brackish estuaries

Juvenile Japanese flounder Paralichthys olivaceus usually inhabit high salinity inshore sandy areas. In June–August 1997, 25 individuals of juvenile Japanese flounder (33–75 mm total length) were collected in the Natori and Nanakita River estuaries in Sendai Bay, Japan. This is the first record of this species being collected in brackish estuaries in which salinities fluctuate from 0 to 30 over a spring tidal cycle. Factors of rainfall, river flow, or year class strength of Japanese flounder were unable to explain the unusual occurrence of this species in the estuaries. The collected juvenile Japanese flounder were considered to have migrated into the estuaries around the time of the passage of an unusually early typhoon that affected this area, indicating the possibility that this species utilizes estuaries for refuge from strong disturbance in its usual habitats. The juveniles fed mainly upon mysids both in the estuaries and the sandy beach area, indicating that estuaries can be a substitute nursery habitat for this species.     

Phase disturbance of 100-kHz groundwaves by a circular island in the open sea

The hyperbolic position fixing of ships by the Decca navigation system utilizes groundwave propagation. But the hyperbolic pattern will be disturbed by an isolated island. The instantaneous phase velocity and the bearing error are calculated from the equiphase lines near the island. It is found numerically and experimentally that the hyperbolic pattern is bent towards the island that is situated on the baseline between the master station and the slave one.     

Chemical studies of dissolved carbohydrates in seawater

Charcoal column chromatography and a dialysis system using a Visking tube were used for the concentration and separation of dissolved carbohydrates in seawater. Recoveries of mono-, oligo-, and polysaccharides were 46–74, 61–89 and 70%, respectively, relative to the total amount of sugars initially submitted to analysis. The combined charcoal column chromatography and dialysis system was used to separate dissolved carbohydrates in seawater samples from Mikawa Bay into mono-, oligo- and polysaccharide fractions. The polysaccharides are separated into two fractions with molecular weights of <4,000 and >4,000 using Sephadex G-25 column chromatography. Monosaccharides, oligosaccharides, polysaccharides with M.W.<4,000 and polysaccharides with M.W. >4,000 accounted for 7–9, 15–26, 7–13 and 20–33% of total dissolved carbohydrates, respectively. However, 32–38% of dissolved carbohydrates were lost during the analytical procedures. Glucose, galactose, mannose, xylose, arabinose, ribose, fucose, and rhamnose were found upon acid hydrolysis of the oligo- and polysaccharide fractions, while fucose and rhamnose were not present in the monosaccharide fraction. Possible sources of the carbohydrates in these fractions are discussed with reference to the monosaccharide composition of cellular carbohydrate in marine algae.     

Photoluminescence properties of thenardite from Ai-Ding Salt Lake,Xinjiang, China

The photoluminescence (PL) spectra, excitation spectra, and PL decay curves of natural, heat-treated, and γ-ray-irradiated thenardites from Ai-Ding Salt Lake, Xinjiang, China, were studied. The natural thenardite under 300 nm excitation showed milk-white luminescence, and the PL spectrum consisted of an extremely broad band with a peak located at approximately 509 nm, spreading over a wide range of UV and visible wavelengths. The excitation spectra, obtained by monitoring the luminescence at 530 nm, consisted of a broad band with a peak located at approximately 235 nm and a flat band spreading over a wide range of UV and visible wavelengths. The PL decay curve of natural thenardite consisted of a fast-decay component with a lifetime of less than 0.1 μs and a slow-decay component with a half-decay time of approximately 0.4 s. The heat treatment of thenardite at 900°C for 20 min reduced the luminescence efficiency to 1/100. The γ-ray irradiation of thenardite reduced the luminescence efficiency to approximately half.     

Position determination at sea using low-frequency radio waves--The effect of a nearby mountain

Measurements of direction-finding (DF) error in position determination based on low-frequency (LF) radio waves were made at sea employing the Decca navigation system. The measured DF error is found to be large when a mountain is nearby. Assuming the mountain to be a hemisphere with complex dielectric constant, we evaluate DF error using electrostatic theory. Analytical predictions of the expected position error caused by the mountain's presence are qualitatively in fairly good agreement with measured values. In connection with this, fluctuations of the electric field intensities are also described.     

Atmospheric carbon dioxide variations at coastal site,Sibukawa, in Seto Inland Sea,Japan. 2. observation from 1980 to 1989

Summary Atmospheric carbon dioxide variations have been studied by using data between May 1980 and July 1989 from Sibukawa in Seto Inland Sea, sited in the western part of Japan. The power spectrum of carbon dioxide shows that the one-day period was predominant and 4 to 5 days period associated with quasiperiodic variation in weather was also significant. The seasonal variation of daily minimum concentration of carbon dioxide shows a maximum in summer months (July–September), and a minimum in winter months (November–December and January–March). The variation pattern seems to be in opposite phase to the carbon dioxide variations expected in the northern hemisphere. This was probably due to reduced vertical mixing under stable stratification of the air layer prevailing during summer months at Sibukawa station. It is noted that the air layer is in lapse conditions during winter months. The annual rate of increase of carbon dioxide concentration is examined using data obtained during winter months. It is 3.1 ppm/year. This value is about twice the increasing rate of increase on a global scale and in the lower troposphere over Japan.With 5 Figures