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31.
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
32.
Xiao-Hua Zhu Arata Kaneko Noriaki Gohda Hideo Inaba Kunio Kutsuwada Marie-Helene Radenac 《Journal of Oceanography》1998,54(2):133-141
During the IOP (Intensive Observation Period) of TOGA/COARE (Tropical Ocean and Global Atmosphere/Coupled Ocean Atmosphere
Response Experiment) from December 1992 to February 1993, four Japanese moored ADCPs (Acoustic Doppler Current Profilers)
measured vertical profiles of three-component velocities at the stations 2S (2°S, 156°E), 2N (2°N, 156°E), 154E (0°N, 154°E)
and 147E (0°N, 147°E). Power spectra of the surface current showed a pronounced peak having a period of around 14 days for
both the zonal and meridional velocities at the stations 2S and 2N near the equator, and for only the meridional velocity
at the equator. This 14-day phenomenon is considered to be a kind of equatorial wave of the first baroclinic mode, from a
comparison of the result of the vertical mode analysis and the vertical distribution of the standard deviation of band-pass
filtered velocity fluctuations. A dispersion relationship obtained from the horizontal mode analysis of this wave confirmed
that the 14-day phenomenon is a mixed Rossby-gravity wave with the westward propagating phase speed and eastward propagating
group velocity. From the cross-spectral analysis of velocity data, the average phase speed and wavelength of the wave were
estimated as 3.64 m s−1 and 3939 km, respectively, for station pair 2S∼147E. These values were in good agreement with the average phase speed and
wavelength of 3.58 m s−1 and 3836 km estimated from the dispersion curve and the observed period. A northerly wind burst blew over all the mooring
sites during the middle of the observation period. The mixed Rossby-gravity wave, which is anti-symmetric for the zonal velocity
about the equator, is likely to be forced by this northerly wind burst crossing the equator. Generation of the oceanic mixed
Rossby-gravity wave of the first baroclinic mode is discussed in association with the atmospheric Rossby wave having the same
period. 相似文献
33.
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
34.
Abdelrahman Mohamed Abdelgawad Kunio Watanabe Mebruk Mohammed Shinji Takeuchi 《Environmental Earth Sciences》2010,60(3):449-462
High levels of fluoride concentration were observed in deep groundwater of the Mizunami area in Central Japan. Fluoride occurs
mainly due to the reaction between granitic basement rock and groundwater. Granites were collected, crushed to powder, and
then allowed to react with purified water for 80 days. Water–rock interaction results showed that the major factor affecting
fluoride concentration is the residence time of the groundwater. Coexisting ions have also some contribution toward fluoride
concentration. The groundwater residence time in the Mizunami area was estimated by applying results of water–rock interaction
to correspond with field data. A regression model relating fluoride concentration, residence time, and coexisting ions was
developed. The parameters of the regression model were determined using the genetic algorithms technique. Residence time was
estimated by extrapolating experimental data to correspond with filed data. Near the recharge area, residence times in the
potential fluoride source rock varied between 1 and 2,000 years, whereas near the discharge area residence times were in excess
of tens of thousands of years. The groundwater residence time was also estimated by the groundwater particle-tracking-flow
model. The estimates of groundwater residence time based on geochemical regression model were often larger than estimates
of groundwater residence time developed by particle-tracking analysis using a groundwater flow model. There were large uncertainties—on
the order of 10–10,000 years—in the estimates based on geochemical data. 相似文献
35.
Abdelrahman M. Abdelgawad Kunio Watanabe Shinji Takeuchi Takashi Mizuno 《Engineering Geology》2009,108(1-2):76-85
The aim of this paper was to explore new factors that might be reasons for the occurrence of fluoride-rich groundwater in the area around a construction site. During the construction of two deep shafts of the Mizunami Underground Research Laboratory (MIU) in Mizunami city, central Japan, a large quantity of groundwater with high fluoride concentration was charged into the shafts. Chemical investigation carried out during the excavation revealed that fluoride concentrations in the area around the MIU site greatly exceeded those prescribed by Japanese standards. Therefore, the origin of fluoride ion was experimentally investigated. Samples were collected from the core of a deep borehole drilled in the study area. The weathering - and alteration levels of the collected granites varied greatly. Granitic powders were used to measure fluoride content in the granitic rock mass. The fluoride content ranged between 200 and 1300 mg/kg. The powders were reacted with purified water for 80 days. The results of water–rock interaction showed granitic rock to be one of the main sources of fluoride-rich groundwater in Mizunami area. Fluoride concentrations in these solutions that were shaken for 80 days varied between 2 and 7 mg/l. This change may have occurred as a result of the spatial distribution of fluoride ions in the granite mass as evidenced by mineralogical analysis of fluoride content in several specimens. X-ray powder diffraction analysis of the rock before- and after the water–rock interaction tests manifested that the presence of fluorite mineral was relatively small compared to other minerals. The degree of weathering and alteration might be an additional factor causing dissolution of fluoride-rich minerals. However, it was difficult to interpret the change in fluorite composition by X-ray diffraction analysis. 相似文献
36.
37.
Temporal change in permeability of the Nojima fault zone by repeated water injection experiments 总被引:8,自引:1,他引:8
Three boreholes were drilled near the Nojima fault, which the 1995 Hyogoken–Nanbu earthquake occurred on. In order to research the properties and the healing process of the fault, water injection experiments were conducted every 3 years. In this report, we researched the permeability of the fault as a measurement of crack density or porosity of the fault zone. Pore water pressure changes in rock due to the water injections at one borehole were observed as discharge changes or groundwater level changes at the other borehole. Using numerical calculations, the permeability of the fault fracture zone was estimated for each experiment. The permeability has been decreasing as time passed, which is thought to show the fault healing process of the Nojima fault after the 1995 Hyogoken–Nanbu earthquake. 相似文献
38.
It is shown that Mie theory predictions of extinction for pure water-ice with the optical constant measured at 100 K do not fit in detail the observed ice absorption feature in infrared objects, although we attempt to explain the observations by considering size distribution and shape of the grains.In addition, based on a similarity between the ice band and the absorption band found in carbon stars, we feel it is questionable whether or not the ice band can really be attributed to the interstellar water-ice. 相似文献
39.
Water injection experiments were performed in 1997, 2000 and 2003 at the 1800 m borehole near the fracture zone of the 1995 Hyogo-ken Nanbu earthquake. During these experiments, a contraction of about 10− 8–10− 7 was observed with three-component strainmeters at a bottom of the 800 m borehole, 70 m southwest of the 1800 m borehole. We estimated hydraulic properties of the fracture zone near the Nojima fault by using the strain data to investigate a healing of the fault during the postseismic stage. We calculated pore pressure changes due to the water injection using Darcy's equation and obtained strain changes due to the pore pressure changes as elastic deformations of the crust. The calculated strain changes have a nearly agreement with the observed strain changes. Hydraulic conductivity in 1997, 2000 and 2003 was determined to be 0.9 ± 0.2 × 10− 6, 0.8 ± 0.2 × 10− 6 and 0.4 ± 0.1 × 10− 6 m/s, respectively. The reduced hydraulic conductivities in 2000 and 2003 suggest that the fractures had been healing. 相似文献
40.
电法探查海岸带含水层咸淡水界面的调查研究 总被引:6,自引:0,他引:6
本文在理论上对电法探查多层土层组成的海岸带含水层的咸淡水界面的可能性进行探讨的基础上,对太平洋沿岸某地区进行了实地调查研究。在测量设置在海岸附近及分布于海岸纵深方向的调查井垂直方向电导率的同时,在调查井附近进行了电法探查。结果表明,电法探查的咸淡水界面的深度与依据井水电导率区分的混合区域上端几乎一致,即对于不同类别土质构成的岩土层,电法不但能探查确定咸淡水界面的深度,而且与以往的手法比较也是一种简单、快速、可靠、成本低廉的确定咸淡水界面深度的方法。 相似文献