Experimental study on strong interaction between regular waves and wind waves—I     

Mitsuhiko Hatori  Masayuki Tokuda  Yoshiaki Toba 《Journal of Oceanography》1981,37(3):111-119

The interaction between mechanically generated regular waves and wind waves is experimentally investigated in a wind-wave tunnel. It is shown that the growth process of regular waves is divided into the four distinct stages as follows: (1) almost independent coexistence of wind waves and regular waves, (2) attenuation of wind waves with simultaneous growth of regular waves, (3) rapid growth of regular waves after disappearance of wind waves, and (4) transition of regular waves to wind waves after the wave breaking. At the second stage there is an apparent relation between the attenuation of wind waves and the growth of regular waves. This fact suggests that there is some strong nonlinear interactions which transfers energy effectively from wind waves to regular waves.  相似文献   

Seasonal changes in the biomass of zooplankton and their food requirement in Funka Bay     

Tsuneo Odate  Yoshiaki Maita 《Journal of Oceanography》1988,44(5):228-234

Zooplankton biomass consisting of large and small-size copepods, copepod nauplii and tintinnids were investigated over a period of one year at two stations in Funka Bay, Japan. The food requirement of zooplankton was also estimated using the method of Ikeda and Motoda. Estimated total carbon requirement of zooplankton in the coastal and central parts of the bay was equivalent to 52 and 38% of the annual primary production, respectively. These corresponded to zooplankton production of 12–13 gC·m^–2·yr^–1.The total carbon requirement at each station increased to 63 and 74% of the primary production during summer compared with 26 and 3% in spring or 19 and 17% in winter. The microzooplankton (copepod nauplii and tintinnids) accounted for about half of the carbon requirement from April to November.Food requirements reached 161% at the coastal station and 194% at the central station of the daily organic carbon production during September. Zooplankton may also feed on carbon sources other than living phytoplankton. This could account for the observed decrease in particulate organic carbon in a water column.Contribution No. 202 from the Research Institute of North Pacific Fisheries, Faculty of Fisheries, Hokkaido University.  相似文献   

Anomalous distribution of suspended matter and some chemical compositions in seawater near the seabed: Transport processes     

Masahiro Kajihara  Katsuhiko Matsunaga  Yoshiaki Maita 《Journal of Oceanography》1974,30(5):232-240

Vertical fine distributions of suspended matter and some chemical compositions in seawater were measured in the layer near the seabed. Distributions of organic suspended matter were almost uniform throughout the layer, but others were anomalous. However, with respect to their peak heights and distribution patterns, the tendency of profiles was the same on the whole. We suggested that these anomalous distributions were primarily caused by the destruction of the large flocculent particle on the seabed and by upward diffusion of disintegrated particles. The similarity of profiles between chemical compositions of dissolved substances and suspended matter of non-dissolved substances, was explained by assuming that pore water in the large particle was simultaneously transported with disintegrated particles after the destruction. An equation for the vertical distribution of suspended matter near the seabed was derived, provided that the rate of destruction of large flocculent particle was in proportion to the current velocity on the seabed. The equation represented the existence of the anomalous distribution, which was continuously changing its pattern. Measurements of vertical profiles of suspended matter showed almost the same tendency with the theory. From the characteristics of the theoretical equation, it was expected that the eddy diffusivity near the seabed was 1050 cm²/sec.  相似文献   

Prediction of ocean waves based on the single-parameter growth equation of wind waves (II) introduction of grid method     

Paimpillil S. Joseph  Sanshiro Kawai  Yoshiaki Toba 《Journal of Oceanography》1981,37(1):9-19

The present study is a modification of the wave prediction model presented in the first paper of this title (Kawai et al., 1979) based on the Toba's (1978) single parameter equation of the wind wave growth. The introduction of a grid method reduces the two defects pointed out inKawai et al., i.e., the absence of the prediction of certain instants at fixed points, and the concentration of wave energy at certain points in the wind direction, arising from the lack of treatment of the lateral spreading of wave energy around the wind direction. The new model is applied to the same set of data. The results shows overall improvements, such as the elimination of certain overestimate in the first study and the coincidence of the predicted maximum with the measured one. The swells are separately hindcasted and a very good agreement with measurement is obtained.  相似文献   

A new expression for the production rate of sea water droplets on the sea surface     

Noriko Iida  Yoshiaki Toba  Masaaki Chaen 《Journal of Oceanography》1992,48(4):439-460

A new set of empirical formulas for the production rate and the number concentration of sea-water droplets on the sea surface are proposed, synthesizing past observation data of sea-salt particles in the sea and water droplets in wind-wave tanks. A new levelz _c is introduced as the effective wind-sea surface where seawater droplets are produced. The new formulas are expressed in linear functions in logarithmic scales ofu*²/v _p , a parameter to describe overall conditions of airsea boundary processes, whereu _* is the friction velocity of air,v the kinematic viscosity of air and _p the peak angular frequency of wind-wave part of wave spectra. A model of coexistence of spray droplets and suspended particles near the sea surface is proposed. As for the independent parameter, a comparison between the uses ofu*²/v _p and ofu _* ³ which was the traditional way of parameterization excluding wave measure, shows that the advantage of usingu*²/v _p is statistically significant with a confidence limit 89% in F-test.  相似文献   

A numerical study on the generation of the small meander of the Kuroshio off southern Kyûshû     

Yoshihiko Sekine  Yoshiaki Toba 《Journal of Oceanography》1981,37(5):234-242

The generation of small meanders of the Kuroshio off southern Kyûshû is investigated. Basing on the fact that the small meanders tend to follow an increase in velocity of the Kuroshio in the Satsunan region (Sekine andToba, 1981), the influence of this velocity increase on the quasi-stationary path of the Kuroshio is studied numerically. Simplified bottom and coastal topographies are employed in a two layer model ocean. A quasi-stationary numerical solution with a constant inflow is used for the initial condition, and a temporal increase in the inflow with corresponding leakage is employed as the boundary condition to investigate nonlinear effects due to the increase in current velocity. Experiments for four different physical models are carried out to determine the specific roles of the continental slope, the planetary-effect, and density stratification. Temporal increase in the inflow tends to cause offshore shift of the current path. But the topographic effect of the continental slope is strong enough that no significant shift of the current path occurs in the case of the barotropic ocean. However, in the case of a baroclinic ocean, temporal increase in the inflow does cause generation of small meanders, because density stratification diminishes the topographic effect. A larger density stratification provides more favorable condition for the appearance of the small meander, and a cyclonic eddy is formed on the continental side of the small meander path.  相似文献   

Local balance in the air-sea boundary processes   总被引：2，自引：0，他引：2  

Yoshiaki Toba 《Journal of Oceanography》1973,29(5):209-220

A combination of the three-second power law, presented in part I for wind waves of simple spectrum, and the similarity of the spectral form of wind waves, leads to a new concept on the energy spectrum of wind waves. It is well substantiated by data from a wind-wave tunnel experiment.In the gravity wave range, the gross form of the high frequency side of the spectrum is proportional tog u _* ^–4, whereg represents the acceleration of gravity,u _* the friction velocity, the angular frequency, and the factor of proportionality is 2.0×l0^–2. The wind waves grow in such a way that the spectrum slides up, keeping its similar form, along the line of the gross form, on the logarithmic diagram of the spectral density,, versus. Also, the terminal value of, at the peak frequency of the fully developed sea, is along a line of the gradient ofg ^{2 –5}.The fine structure of the spectrum from the wind-wave tunnel experiment shows a characteristic form oscillating around the ^–4-line. The excess of the energy density concentrates around the peak frequency and the second- and the third-order harmonics, and the deficit occurs in the middle of these frequencies. This form of the fine structure is always similar in the gravity wave range, in purely controlled conditions such as in a wind-wave tunnel. Moving averages of these spectra tend very close to the form proportional to ^–5.As the wave number becomes large, the effect of surface tension is incorporated, and the ^–4-line in the gravity wave range gradually continues to a ^–8/3-line in the capillary wave range, in accordance with the wind-wave tunnel data. Likewise, the ^–5-line gradually continues to a ^–7/3-line.Also, through a discussion on these results, is suggested the existence of a kind of general similarity in the structure of wind wave field.  相似文献   

Obituary: Professor Yasuo Miyake     

Yoshiaki Toba 《Journal of Oceanography》1990,46(5):195-200

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The role of atmospheric nuclear explosions on the stagnation of global warming in the mid 20th century     

Yoshiaki Fujii 《Journal of Atmospheric and Solar》2011,73(5-6):643-652

This study suggests that the cause of the stagnation in global warming in the mid 20th century was the atmospheric nuclear explosions detonated between 1945 and 1980. The estimated GST drop due to fine dust from the actual atmospheric nuclear explosions based on the published simulation results by other researchers (a single column model and Atmosphere-Ocean General Circulation Model) has served to explain the stagnation in global warming. Atmospheric nuclear explosions can be regarded as full-scale in situ tests for nuclear winter. The non-negligible amount of GST drop from the actual atmospheric explosions suggests that nuclear winter is not just a theory but has actually occurred, albeit on a small scale. The accuracy of the simulations of GST by IPCC would also be improved significantly by introducing the influence of fine dust from the actual atmospheric nuclear explosions into their climate models; thus, global warming behavior could be more accurately predicted.  相似文献   

Olivine-rich exposures in the South Pole-Aitken Basin     

Satoru Yamamoto  Ryosuke Nakamura  Tsuneo Matsunaga  Yoshiko Ogawa  Yoshiaki Ishihara  Tomokatsu Morota  Naru Hirata  Makiko Ohtake  Takahiro Hiroi  Yasuhiro Yokota  Junichi Haruyama 《Icarus》2012,218(1):331-344

The distribution and the geological context of the olivine-rich exposures in the South Pole-Aitken (SPA) Basin on the Moon were investigated based on the spectral data obtained from the Spectral Profiler (SP) and Multiband Imager (MI) onboard the Japanese lunar explorer Kaguya/SELENE. The olivine-rich exposures are found only in the peak rings or central peaks of the Schrödinger basin and Zeeman crater, which are located in the outer region of the SPA Basin and not in the center region. On a localized scale, the olivine-rich materials are exposed on landslide features on the crater walls or sloped wall of the central peaks or the peak rings. Another observational finding is the co-existence of olivine-rich and plagioclase-rich materials on a kilometer scale spanning most of the olivine-rich sites in the Schrödinger basin. Pyroxene-rich materials are found in fresh craters outside the peak rings or the central peaks with olivine-rich materials. Based on these results, the following scenario are proposed: (1) the impact to form the SPA Basin melted a large amount of the lunar upper mantle and crust, and distributed the melted materials to the outer region; (2) local differentiation of melted materials hid the olivine-rich materials in the center region of the SPA Basin; (3) later impacts that formed the Schrödinger and Zeeman craters excavated and exposed the olivine-rich materials to the surface again; and (4) space weathering and regolith gardening obscured the olivine-rich spectra at the exposure sites, but recent, small scale impacts or landslides on the sloped wall exposed fresh olivine-rich materials, allowing the identification of the olivine-rich exposures by spectral remote-sensing. This suggests that several, different scale events play an important role in forming the surface distributions of originally deep-seated materials on the Moon, as well as on other planetary bodies.  相似文献