Horizontal electric fields in the middle latitude     

Ogawa Toshio  Tanaka Yoshikazu  Huzita Akira  Yasuhara Michihiro 《Planetary and Space Science》1975,23(5):825-830

Three dimensional electric fields were measured at the altitude of about 27 km in the stratosphere over the Pacific Ocean about 200–400 km away from the Sanriku coast of Honsyu Island (L = 1·4) on 16–17 October 1973, which was magnetically disturbed. The average horizontal electric field thus measured is about 10 mV/m, and the electric field vectors made clockwise semidiurnal rotations rather than diurnal. Daily variation of this electric field was compared with data at L = 2·7–3·5 published by Mozer (1973) and was found to be very similar. This suggests that these electric fields are of common origin in the plasmasphere. From their mean daily variation it is estimated that the plasmaspheric convection is decreased in the night side and is increased in the day side by 200–300 m/sec, and there is an outward flow in the first half of the afternoon and an inward flow in the plasma bulge region of about 500 m/sec.  相似文献   

Diel Changes in Vertical Distribution and Feeding Conditions of the Chaetognath Parasagitta elegans (Verill) in the Subarctic Pacific in Summer     

Sohey Matsuda  Akira Taniguchi 《Journal of Oceanography》2001,57(3):353-360

Diel changes in vertical distribution and feeding conditions of the chaetognath Parasagitta elegans (Verill) were observed in three regions of the subarctic North Pacific in the summer of 1997. Samples were collected by repeated vertical hauls with a Vertical Multiple Plankton Sampler (VMPS) for 15–45 hours by demarcating the 0–500 m water column into four sampling layers. Integrated abundance through the entire water column and the proportion of juveniles were higher in the Bering Sea than the western and eastern subarctic Pacific. Juveniles always inhabited the surface layer in the western subarctic Pacific and Bering Sea, but they inhabited the underlying layer in the eastern subarctic Pacific. Stages I–III concentrated into the upper 150 m in the western subarctic Pacific but were distributed widely from 20–300 m in the Bering Sea. Among them, Stages II and III migrated rather synchronously over a wide vertical range in the eastern subarctic Pacific. The feeding rate of P. elegans was calculated to be 0.18 prey/chaetognath/day in the western subarctic Pacific, 0.27 prey/chaetognath/day in the Bering Sea and 0.07 prey/chaetognath/day in the eastern subarctic Pacific.  相似文献   

Formation of water masses and fronts due to density-induced current system     

Akira Harashima  Yukio Oonishi  Hideaki Kunishi 《Journal of Oceanography》1978,34(2):57-66

Several numerical experiments were carried out on the formation of water masses and their fronts such as observed in the Kii Channel in winter. Such water masses and fronts may caused by density-induced current system. The phenomenon is assumed to take place in the vertical two-dimensional plane not involving the effect of the earth's rotation. The linear momentum equation and the diffusion-advection equations of salinity and temperature are integrated with respect to time under a vertically hydrostatic condition. The result is that two rolls which correspond to the onshore water mass and the offshore water mass are formed with an accompanying front between them. The apparent diffusion coefficient reaches a relatively great amount inside the water masses and drops down to the eddy diffusivity level at the front. The dependence of the synoptic distributions of the temperature and salinity on several parameters is also examined. Finally another experiment is carried out involving the effect of the earth's rotation, which results in a rather different distribution pattern from that of the non-rotating model.  相似文献   

The roughness height and drag law over the water surface based on the hypothesis of local equilibrium     

Tadao Kusaba  Akira Masuda 《Journal of Oceanography》1988,44(4):200-214

A series of measurements of winds and wind-waves were carried out in wind-wave flumes. A data analysis based on the hypothesis of local equilibrium yielded a new empirical formula on the controversial quantity of roughness heightz ₀ over the water surface: , where the nondimensional roughness height is defined bygz ₀/u _* ² and the wave-wind parameterũ byω _p u _*/g, g being the gravitational acceleration,u _* the friction velocity of air,ω _p the peak frequency of wind-wave spectra. The obtained formula is compared with Charnock's (1955) and Toba's (1979) proposals; is constant in the former and inversely proportional toũ in the latter. As in Toba's, this formula immediately leads to a practically important conclusion that the drag coefficientC _d depends not merely on the usual variableU ₁₀ (wind velocity at 10m height over the water surface), but also on the surface state represented by wind-waves. An explicit expression is provided for the drag coefficient incorporating the wave-wind parameter; it covers the range ofC _d calculated from most of the previous drag formulas, by varying the wave-wind parameter.  相似文献   

Influence of Salinity on pH and Aluminum Concentration on the Interaction of Acidic Red Soil with Seawater   总被引：1，自引：0，他引：1  

Mohamed?M.?Kombo  Said?A.?Vuai  Maki?Ishiki  Akira?TokuyamaEmail author 《Journal of Oceanography》2005,61(3):591-601

Contamination of acidic red soil in the coastal areas of Okinawa Islands is a serious environmental problem. This study was conducted to examine the effects of the salinity on pH and aluminum concentration when the acidic red soil interacts with seawater. Acidic red soil from Gushikawa recreation center was fractionated into bulk soil, coarse sand and silt + clay. Different weights of each fraction were equilibrated with seawater solutions. The pH and concentrations of Al³⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺ were then analyzed in the extracts. The results showed a decreasing trend of pH with increasing soil to solution ratio while the extracted Al³⁺ revealed an increasing trend. The lowest pH values were 3.85, 4.06, 4.41, 4.66 and their corresponding highest Al³⁺ concentrations were 2.50, 1.01, 0.062 and 0.036 mmolL⁻¹ in the seawater extracts, one-tenth seawater extracts, one-hundredth seawater extracts and one-thousandth seawater solution extracts, respectively. Mostly, the concentrations of Na⁺, Ca²⁺, Mg²⁺ and especially K⁺ decreased with increasing soil weight in the high salinities but showed the opposite trend in the low salinity samples. Potassium concentration decreased by 39%, 53% and 40% in the seawater extracts, one-tenth and one-hundredth seawater extracts but increased by 200% in one-thousandth seawater extracts. The coincidence of the increase in Al³⁺ and H⁺ concentrations, and the decrease of Na⁺, K⁺, Ca²⁺ and Mg²⁺ concentrations in the solutions suggests ion exchange/adsorption, while the increased patterns, particularly at low salinity could be attributed to the dissolution of the species from the soils.  相似文献   

VII-3 Shore based wave energy conversion system development     

Akira Hiramoto  Ichizo Tamaki  Yoshio Masuda 《Ocean Engineering》1985,12(6):595-596

  相似文献   

Wind-wave spectra based on the hypothesis of local equilibrium     

Tadao Kusaba  Akira Masuda 《Journal of Oceanography》1989,45(1):45-64

Wind-wave spectra measured in a wind-flume are analyzed according to the hypothesis of local equilibrium. The gross relation between the wave height and the frequency is reexamined to yield the basic validity of the 3/2-power law of Toba orE～? in the range of 0.4≦?≦1, where? is the wave-wind parameter defined by?=ω _p u _*/g; ω _p denotes the peak frequency of the wind-wave spectra,u _* the friction velocity andg the gravitational acceleration. Noticeable deviation is found, however, for?<0.4 or?>1. In particular, the data for large? suggest the existence of an upper limit of the wave nonlinearityE at about 5×10^?2, whereE=Eω _p ⁴ /g² withE the total power of the wind wave spectrum. Then, the spectral form is investigated in detail. As? decreases, the normalized spectrum becomes more gradual as a whole, but its forward (low frequency) part tends to show a steeper profile. In the high frequency region ( \(\tilde \omega \) >2.6), the spectrum is found to have a functional form likeu _* ² ω ^?3, which differs from the usualω-dependence asω ^?5 orω ^?4. It suggests weak dependence of the high-frequency spectra on the gravitational accelerationg and on the peak frequencyω _p ; spectral density at high frequencies may be saturated, so that its magnitude may be dominated by the frequencyω, the friction velocityu _*, the surface tension and the viscosity.  相似文献   

Rates of net assimilation and respiration of amino acids by marine bacteria     

Yoshiaki Maita  Mitsuru Yanada  Akira Rikuta 《Journal of Oceanography》1974,30(1):1-9

The selectivity of amino acid assimilation by marine bacteria was examined using seven kinds of¹⁴C-amino acids and the acid hydrolysate of¹⁴C-labelled proteins. It was found that the net assimilation and respiration by marine bacteria followed MICHAELIS-MENTEN kinetics for all of amino acids used in our experiments. Maximum velocities of amino acids were 0.01 to 0.19g carbon/hour per 2×10⁷ cells for net assimilation and less than 0.18g carbon/hour per 2×10⁷ cells for respiration at 20C. The velocity of gross assimilation was found with the following order: phenylalanine>valine, glutamic acid>serine, arginine>tryptophan>glycine. The assimilation velocities of amino acids in these laboratory works showed almost the same order as those in field experiments. The assimilation velocity of an amino acid was influenced by coexisting another amino acids or glucose. The assimilation velocity in lower substrate range of amino acids was directly proportional to the number of bacterial cells in the range from 6×10² to 3×10⁴ cells per ml. No linear relation between the assimilation velocity of amino acids and reciprocal of absolute temperature was found, but a marked bending was observed at 15 to 20C. The velocity at the optimum temperature was three to six times of that at 5C.  相似文献   

Simultaneous Measurement of Hydrogen Peroxide and Fe Species (Fe(II) and Fe<Subscript>(tot)</Subscript>) in Okinawa Island Seawater: Impacts of Red Soil Pollution     

Takemitsu?ArakakiEmail author  Hiroyuki?Fujimura  Asha?Mansour?Hamdun  Kouichirou?Okada  Hiroaki?Kondo  Tamotsu?Oomori  Akira?Tanahara  Hatsuo?Taira 《Journal of Oceanography》2005,61(3):561-568

The northern part of Okinawa Island suffers from red soil pollution—runoff of red soil into coastal seawater—which damages coastal ecosystems and scenery. To elucidate the impacts of red soil pollution on the oxidizing power of seawater, hydrogen peroxide (HOOH) and iron species including Fe(II) and total iron (Fe_(tot), defined as the sum of Fe(II) and Fe(III)) were measured simultaneously in seawater from Taira Bay (red-soil-polluted sea) and Sesoko Island (unpolluted sea), off the northern part of Okinawa Island, Japan. We performed simultaneous measurements of HOOH and Fe(II) because the reaction between HOOH and Fe(II) forms hydroxyl radical (•OH), the most potent environmental oxidant. Gas-phase HOOH concentrations were also measured to better understand the sources of HOOH in seawater. Both HOOH and Fe(II) in seawater showed a clear diurnal variation, i.e. higher in the daytime and lower at night, while Fe_(tot) concentrations were relatively constant throughout the sampling period. Fe(II) and Fe_(tot) concentrations were approximately 58% and 19% higher in red-soil-polluted seawater than in unpolluted seawater. Gas-phase HOOH and seawater HOOH concentrations were comparable at both sampling sites, ranging from 1.4 to 5.4 ppbv in air and 30 to 160 nM in seawater. Since Fe(II) concentrations were higher in red-soil-polluted seawater while concentrations of HOOH were similar, •OH would form faster in red-soil-polluted seawater than in unpolluted seawater. Since the major scavenger of •OH, Br⁻, is expected to have similar concentrations at both sites, red-soil-polluted seawater is expected to have higher steady-state •OH concentrations.  相似文献   

Standing Crops of Planktonic Ciliates and Copepod Nauplii in the Subarctic North Pacific and the Bering Sea in Summer     

Hiroshi Ito  Akira Taniguchi 《Journal of Oceanography》2001,57(3):333-339

Abundances and biomasses of planktonic ciliates and copepod nauplii, major components of the microzooplankton community, were investigated in the subarctic North Pacific and the Bering Sea in summer of 1997. Their regional variation was illustrated by demarcating the entire area into five regions. Ciliates always predominated both in abundance (>94%) and biomass (>78%) over nauplii. Regional means of ciliates in the water column were higher in the Alaskan Gyre (120 × 10⁶ cells/m²) and the Western Subarctic Gyre (110 × 10⁶ cells/m²) in terms of abundance, and rich in the Bering Sea Gyre (360 mgC/m²) and the Western Subarctic Gyre (340 mgC/m²) in terms of biomass. By contrast, standing crops of ciliates were poor in the Oyashio Region (67 × 10⁶ cells/m²; 170 mgC/m²) and the Transition Region (64 × 10⁶ cells/m²; 160 mgC/m²). The values of biomass reported here are generally in agreement with the values reported previously from the Bering Sea Gyre and the Alaskan Gyre but are considerably higher than the previous value found in the Western Subarctic Gyre. No significant correlations could be found between chlorophyll a crop and standing crops of ciliates and copepod nauplii over the entire subarctic North Pacific and the Bering Sea during this summer.  相似文献