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22.
Field surveys and in situ experiments were conducted in the shallow Matsukawa-ura in summer to evaluate the biological efficiencies of shallow-water areas for preserving coastal ecosystems. In Matsukawa-ura (5.8 km(2)), the suspension-feeding bivalves Ruditapes philippinarum and Crassostrea gigas were the dominant animals--their total biomasses (wet weight) were estimated to be 3.4 x 10(6) and 2.3 x 10(6) kg, respectively. Ulva sp. and Zostera marina were the dominant macrophyte species during the summer, with standing crops estimated to be 0.29 x 10(6) and 0.20 x 10(6) kg, respectively. The dissolved inorganic nitrogen (DIN) uptake rates for Ulva sp. and Z. marina were determined by in situ experiments. An ecological model calculated on the basis of the observed dataset showed that, in comparison with tidal exchange, a significant amount of particulate organic matter was removed by bivalve filtration and a considerable quantity of DIN was removed by macrophyte species. 相似文献
23.
Five main deformation units, discrete sheets of deformed sediments that lie between a significant thickness of undeformed sediment, were selected for study within Late Pleistocene lacustrine sands and clays in the Onikobe and Nakayamadaira Basins, northeastern Japan. The deformed units show evidence of deformation by a variety of mechanisms including fluidization, liquefaction, brittle failure and cohesive flow. Driving forces are thought to be primarily reverse density gradient systems, but also include gravitational body force, shear stress and unequal loading. The main trigger mechanisms are firstly earthquakes, secondly overloading from volcanic sands and thirdly, to a lesser extent, subaqueous currents. Consideration is given to criteria that allow the trigger mechanism to be identified. This study shows that the following criteria can be used to identify a seismic triggering agent: (i) setting; (ii) the extent of the deformation units; (iii) absence of evidence relating to other potential trigger mechanisms; and (iv) evidence relating to other potential trigger mechanisms is present but can be seen elsewhere in the stratigraphic section associated with undeformed sediment. Conversely, the following criteria, while they are important in interpreting the driving force and deformation mechanism, have no relevance to the trigger mechanism: (i) sediment composition; (ii) deformation structures being restricted to a single stratigraphic interval (<1 m thick) (not necessarily correlatable over large areas); and (iii) similarity to structures in the literature. 相似文献
24.
The air–sea ice CO2 flux was measured over landfast sea ice in the Chukchi Sea, off Barrow, Alaska in late May 2008 with a chamber technique. The ice cover transitioned from a cold early spring to a warm late spring state, with an increase in air temperature and incipient surface melt. During melt, brine salinity and brine dissolved inorganic carbon concentration (DIC) decreased from 67.3 to 18.7 and 3977.6 to 1163.5 μmol kg−1, respectively. In contrast, the salinity and DIC of under-ice water at depths of 3 and 5 m below the ice surface remained almost constant with average values of 32.4±0.3 (standard deviation) and 2163.1±16.8 μmol kg−1, respectively. The air–sea ice CO2 flux decreased from +0.7 to −1.0 mmol m−2 day−1 (where a positive value indicates CO2 being released to the atmosphere from the ice surface). During this early to late spring transition, brought on by surface melt, sea ice shifted from a source to a sink for atmospheric CO2, with a rapid decrease of brine DIC likely associated with a decrease in the partial pressure of CO2 of brine from a supersaturated to an undersaturated state compared to the atmosphere. Formation of superimposed ice coincident with melt was not sufficient to shut down ice–air gas exchange. 相似文献
25.
In this paper, based on the basic equations of water flow and heat transfer, the hydrothermal coupling model is established.The numerical model was realized in COMSOL Multiphysics software, and simulation results are compared with the experimental results of Watanabe and Wake(2008) to verify the effectiveness of the model. Through the calculation, we can obtain the dynamic changes of heat and water fluxes, thermal and hydrological properties, matric potential and temperature gradient in unsaturated freezing soil; and these variables are unmeasurable in practice. 相似文献
26.
Significant fluctuations of the currents of the tidal frequencies have been detected in the Kuroshio Current northeast of Taiwan and in the Tokara Strait, with total amplitudes comparable to the mean surface current (about 4050 cm s−1). At the continental shelf the tidal signal varies considerably with distance from the axis of the Kuroshio. Tidal ellipses on the continental shelf consistently have major axes in the northwest-southeast direction. Because tidal signals in the Kuroshio regions have very small spatial scales, they may not be caused by the barotropic tide but the baroclinic tide. It is inferred that the Kuroshio interacts with the baroclinic tides over the continental slope. 相似文献
27.
Masahisa Kubota Naoto Iwasaka Shoichi Kizu Masanori Konda Kunio Kutsuwada 《Journal of Oceanography》2002,58(1):213-225
We have constructed ocean surface data sets using mainly satellite data and called them Japanese Ocean Flux data sets with
Use of Remote sensing Observations (J-OFURO). The data sets include shortwave radiation, longwave radiation, latent heat flux,
sensible heat flux, and momentum flux etc. This article introduces J-OFURO and compares it with other global flux data sets
such as European Centre for Medium Range Weather Forecasting (ECMWF) and National Center for Environmental Prediction (NCEP)
reanalysis data and da Silva et al. (1994). The usual ECMWF data are used for comparison of zonal wind. The comparison is carried out for a meridional profile
along the dateline for January and July 1993. Although the overall spatial variation is common for all the products, there
is a large difference between them in places. J-OFURO shortwave radiation in July shows larger meridional contrast than other
data sets. On the other hand, J-OFURO underestimates longwave radiation flux at low- and mid-latitudes in the Southern Hemisphere.
J-OFURO latent heat flux in January overestimates at 10°N–20°N and underestimates at 25°N–40°N. Finally, J-OFURO shows a larger
oceanic net heat loss at 10°N–20°N and a smaller loss north of 20°N in January. The data of da Silva et al. in July show small net heat loss around 20°S and large gain around 20°N, while the NCEP reanalysis (NRA) data show the opposite.
The da Silva et al. zonal wind speed overestimates at low-latitudes in January, while ECMWF wind data seem to underestimate the easterlies.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
28.
Kunio Kutsuwada 《Journal of Oceanography》1982,38(3):159-171
The wind-stress field in the North Pacific Ocean during 1961–75 is computed from nearly five million ship reports. With a drag coefficient having a linear relation to wind speed, annual mean and monthly mean wind-stress fields are obtained, and their features are described.Compared with the stress fields obtained byHellerman (1967) andWyrtki andMeyers (1976), the eastward component of the stress in the present study is larger in magnitude and the northward one smaller in magnitude, especially in the trade wind region. Differences in the drag coefficient do not have a pronounced effect on the estimated stress field. Long-period inter-annual variations in the wind field are the most likely cause of the discrepancies between the present study and those of the above authors.The maximum of the wind-stress curl, estimated from the annual mean wind-stress fields, is as large as 1.0×10–8dyn cm–3 around 30°N, and is larger than that estimated byEvenson andVeronis (1975). The discrepancy is considered to be mainly due to differences in the computed stress field itself rather than due to differences in the grid size used in the stress computations.The Sverdrup transports integrated from the eastern boundary on the basis of the present stress field have a maximum greater than 40×10–12cm3 s–1 (Sv.) near the western boundary around 30°N. This value is closer to the observed transport of the Kuroshio than that based on Hellerman's stress field. 相似文献
29.
Kunio Kutsuwada 《Journal of Oceanography》1989,45(2):154-165
In January–February 1987, an urgent cruise JENEX-87 was carried out in the central equatorial Pacific during the occurrence of the 1986–87 El Niño. This cruise, supported by the Japan Science and Technology Agency, supplied heat flux data through the sea surface, on the basis of direct measurements of short- and long-wave radiation fluxes.In the time average, the heat gain due to the radiation flux (153 W m–2) was almost compensated by the heat loss due to latent heat flux (130 W m–2), and thus the net heat gain was small in magnitude (20 W m–2). On the other hand, day-to-day changes of the net heat flux ranged within ±130 W m–2, mainly reflecting the downward short-wave radiation variations.The heat balance in the surface oceanic mixed layer was investigated in two quadrangle areas (160°E-180° and 180°-160°W between 2°N and 2°S), using the surface heat flux and estimating the advective heat fluxes due to the geostrophic and Ekman currents. In these two quadrangles, we respectively derived –187±88 W m–2 and +27±95 W m–2. The former value, which is equivalent to about 1°C month–1 drop of the mixed layer temperature, is evidence of the abnormal oceanic condition in the occurrence of the 1986–87 El Niño event. 相似文献
30.
Minoru Ando Tetsuya Nagata Shuji Sato Makoto Watanabe Kunio Itoh Toshihide Kawai Hidehiko Nakaya Yoshiharu Namba Takeshi Takezawa 《Experimental Astronomy》2002,13(3):119-134
We constructed a wide field cryogenic telescope (WFCT) containing a whole Ritchey-Chrétien system and a focal plane array
in a cryostat for near infrared observations to cover the field of view of 0.4°. The telescope has a primary mirror of 220
mm and an engineering grade 256 × 256 InSb array. The optical components such as two mirrors, filters, spiders, and radiation
shield tube are cooled down to 180 K as well as the InSb array to 35 K by a mechanical refrigerator. We show the results of
the background surface brightnesses and the limiting magnitudes at 3.3 and 3.67 μm measured at Sutherland, South Africa. We
describe the on-going upgrade of this instrument, equipped with a 1024 × 1024 ALADDIN InSb science grade array.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献