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31.
Interannual variations of biomass of major mesozooplankton groups (Cnidaria, Chaetognatha, Copepoda, Crustacea other than
copepods, Tunicata) in the January to March period were examined in the slope, Kuroshio and offshore waters off the Pacific
coast of western Japan (western region) from 1971 to 1988 and off central Japan (central region) from 1971 to 1989. The mean
biomass for each year of most of the mesozooplankton groups was high in the early 1970s and tended to decrease (in the western
region) or to have dropped to a lower level (in the central region) after the mid-1970s. Stepwise multiple linear regression
analyses of the mean biomass for each year of each mesozooplankton group in the Kuroshio in both regions against climatic
factors revealed that the biomass was related positively to wind speed. It is therefore considered that the nutrient supply
to the upper layers limits the production of many of the mesozooplankton groups examined in the Kuroshio, even in winter.
Similar relationships were also found for the biomass of Copepoda, non-copepod Crustacea and Tunicata in the offshore water
in the western region. The percentage of copepods in the biomass in the central region seemed to decrease under high water
temperature conditions, while that of Chaetgnatha tended to increase. Climatic factors thus largely influenced the interannual
variations of biomass and composition of mesozooplankton in and near the Kuroshio during the winter to early spring period.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
32.
33.
Current records obtained in the inshore region along the Fukushima coast are analyzed. The existence of periodical current fluctuations whose period is about 100 hours and whose amplitude is as large as 15–25cm s–1 is recognized. Auto-spectral analyses are made also for sea level, atmospheric pressure and wind records. Each spectrum has significant peaks at the similar period to the current spectrum. The wind spectrum has a broad peak compared with the current. The periodical current fluctuations propagate southward with speed of 3–5 km h–1. These propagation speeds seem to correspond to those of the second-and third-mode shelf waves. 相似文献
34.
Abstract We have studied the behavior of nonlinear waves in isothermal atmospheres using an improved beam scheme method. It is shown that although the magnitude of the mass leakage due to side beams is significant, nevertheless in a motion close to hydrostatic equilibrium it can be suppressed, if special density distributions and/or suitable mesh intervals are selected. We adopt as the parameters for our model of the atmospheres M=1 M[odot], R=50 R[odot] and T=4864 K. The time variation of the physical quantities in each cell is found for several oscillation periods. The critical frequency for the model atmosphere in the case of waves with a weak nonlinearity seems to be consistent with that in the linear theory. 相似文献
35.
Deborah L. Domingue Scott L. Murchie Brett W. Denevi Nancy L. Chabot David T. Blewett Nori R. Laslo Robin M. Vaughan Hong K. Kang Michael K. Shepard 《Planetary and Space Science》2011,59(15):1873-1887
During the third flyby of Mercury by the MESSENGER spacecraft, a dedicated disk-integrated photometric sequence was acquired with the wide-angle multispectral camera to observe Mercury's global photometric behavior in 11 spectral filters over as broad a range of phase angle as possible within the geometric constraints of the flyby. Extraction of disk-integrated measurements from images acquired during this sequence required careful accounting for scattered light and residual background effects. The photometric model fit to these measurements is shown to fit observed radiances at phase angles below 110°, possibly except where both solar incidence and emission angles are high (>70°). The complexity of the scattered light at wavelengths greater than 828 nm contributes to a less accurate photometric correction at these wavelengths. The model is used to correct the global imaging data set acquired at a variety of geometries to a common geometry of incidence angle=30°, emission angle=0°, and phase angle=30°, yielding a relatively seamless mosaic. The results here will be used to correct image mosaics of Mercury acquired in orbit. 相似文献
36.
H.Shirai Y.Kamide E.A.Kihn B.Hausman M.Shinohara H.Nakata M.Isowa T.K.Takada Y.Watanabe S.Masuda 《中国天文和天体物理学报》2003,3(4):375-380
This paper presents the recent progress in our project of estimating near real-time electric fields and currents in the ionosphere through our computer system called the Geospace Environment Data Analysis System (GEDAS). We show a new technique in which data from ground magnetometers are collected by the system and used as input for the KRM and AMIE programs to calculate the distribution of ionospheric electric fields and currents, as well as of other ionospheric parameters, such as electric potential patterns. One of the goals of this project is to specify ionospheric processes. Examples of the near real-time calculation and the data flow of our scheme are presented. 相似文献
37.
Calcium and magnesium‐bearing sabugalite occurs as aggregations of yellowish platy crystals in veinlets or druses in conglomerate from the oxidized parts of the Tono uranium deposit, Central Japan. X‐ray powder diffractometry of this mineral has reflections consistent with previous powder diffraction data of sabugalite. It is included in the monoclinic system with space group C2/m and calculated cell parameters of a = 19.68Å, b = 9.89Å, c = 9.82Å α = γ = 90°, β‐96.93° and V = 1897.83Å3. Chemical analysis yields a formula of (Ca0.10 Mg0.09)Σ0.19Al0.53(UO2)2.04((PO4)1.99(AsO4)0.01)Σ2.00·11.22H2O. EMPA mapping shows that the mineral is compositionally uniform with no micron‐scale layering. Charge of cations including Ca and Mg in the cation‐H2O layer is 1.98 being identical to that of autunite group minerals. This suggests that the charge balance in the cation‐H2O layer of the mineral could be made by the alkaline earth or alkaline elements rather than by hydrogen ions. 相似文献
38.
Ryoko Nakata Shin’ichi Miyazaki Mamoru Hyodo Takane Hori 《Marine Geophysical Researches》2014,35(3):311-317
The Hyuga-nada region of southwest Japan, which is located off the east coast of Kyushu Island, may have the potential to generate great interplate earthquakes along the Nankai trough in the future. In this area, thrust earthquakes of M = 6.7–7.2 have occurred with recurrence intervals of approximately 30 years. In association with these earthquakes, possible local heterogeneities of plate coupling may be expected within 100 km from the coast in the Hyuga-nada region. We investigate numerical experiments to determine the spatial and temporal resolution of slip on the plate interface beneath the Hyuga-nada offshore region. For this purpose, we calculated synthetic displacement data from the result of numerical simulation conducted for the afterslip following an Mw 6.8 earthquake, for existing global positioning system stations on land and planned ocean floor seismic network stations. The spatial and temporal distribution of fault slip is then estimated using a Kalman filter-based inversion. The slip distribution estimated by using ocean floor stations demonstrates that the heterogeneity of plate coupling is resolved approximately within 50 km from the coastal area. This heterogeneity corresponds to the coseismic area of an Mw 6.8 earthquake with a radius of 10 km. Our study quantitatively evaluates the spatial resolution of aseismic slip in the Hyuga-nada region. Analysis based on continuous ocean floor data is useful for resolving the spatial variations of heterogeneities in plate couplings. 相似文献
39.
Microbial community respiration and structure of dead zone sediments of Omura Bay, Japan 总被引:1,自引:0,他引:1
Minoru Wada Shotaro Suzuki Tadashi Nara Yu Umezawa Motohiro Shimanaga Kazumi Matsuoka Hideaki Nakata 《Journal of Oceanography》2012,68(6):857-867
Monitoring sediment microbial community metabolism and structure is instrumental to understanding biogeochemical processes in and ecological impacts on bottom environments. The aim of this study was to determine potential community respiration and to reveal community dynamics of the microorganisms in the dead zone sediments of Omura Bay, Japan. The bay is highly enclosed and develops severe hypoxia in the central regions every summer. We collected sediment core samples from the center of the bay during hypoxia, estimated sediment oxygen consumption by using an adapted in vivo electron transport system activity (in vivo ETSA) assay, enumerated abundance of bacteria, and analyzed bacterial community structure by automated ribosomal intergenic spacer analysis. Higher ETSA and bacterial diversity were found in upper sediments (within 3?cm depth) from the center than the fringe of the bay. Sediment bacterial community structure of the bay center was distinct from that of the fringe. From these results, upper sediment in the dead zone of Omura Bay was characterized by (1) greater community respiration and (2) greater diversity of bacterial components compared with the non-hypoxic sediment of the bay fringe. These characteristics have important implications for understanding the interaction between microbial communities and the development of hypoxia in Omura Bay. 相似文献
40.
To understand when oxygen-depleted waters occur, how they develop and when they dissipate in inner Tokyo Bay, realistic simulations were attempted with fine spatial and temporal resolution by applying realistic time dependent external forcing. A 3D hydrodynamic model was driven by time-dependent external forcing factors/parameters such as solar radiation, air temperature, relative humidity, wind velocity, and fluvial discharge, under the open boundary conditions of 1995. A simulated time series of salinity and temperature agreed fairly well with observed data, except in summer. The model failed to reproduce the development of the surface mixed layer in summer. Several sensitivity analyses on the external forcing parameters such as wind velocity and vertical diffusivity were conducted to reproduce the mixed layer. However, changing these parameter values did not improve the model results. 相似文献