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1.
The fall-rate of the T-5 expendable bathythermograph (XBT) produced by Tsurumi Seiki (TSK) Co., Ltd and that by Sippican Inc., are intercompared by a series of contemporaneous and colocated measurements with conductivity-temperature-depth (CTD) profilers. It is confirmed that the fall-rates of the two manufacturers' T-5 differ by about 5 percent, despite the fact that they had been believed to be identical for many years. The cause of the difference is discussed on the basis of a detailed cross-examination of the two T-5 models. It is found for the first time that the two models are different in several respects. The manufacturer's fall-rate equation is only applicable to the Sippican T-5, for which Boyd and Linzell's (1993) equation seems to be slightly more accurate. Kizu et al.'s (2005) equation gives a clearly less biased depth than the manufacturers' equation for the TSK T-5. It is also found that the fall-rates of both T-5 models are dependent on water temperature, perhaps because of viscosity. The temperature-dependency of the fall-rate of the TSK T-5 is larger than that of the Sippican T-5.  相似文献   

2.
The wave transmission, reflection and energy dissipation characteristics of ‘’-type breakwaters were studied using physical models. Regular and random waves in a wide range of wave heights and periods and a constant water depth were used. Five different depths of immersion (two emerged, one surface flushing and two submerged conditions) of this breakwater were selected. The coefficient of transmission, Kt, and coefficient of reflection, Kr, were obtained from the measurements, and the coefficient of energy loss, Kl was calculated using the law of balance of energy. It was found that the wave transmission is significantly reduced with increased relative water depth, d/L, whether the vertical barrier of the breakwater is surface piercing or submerged, where ‘d’ is the water depth and ‘L’ is the wave length. The wave reflection decreases and energy loss increases with increased wave steepness, especially when the top tip of the vertical barrier of this breakwater is kept at still water level (SWL). For any incident wave climate (moderate or storm waves), the wave transmission consistently decreases and the reflection increases with increased relative depth of immersion, Δ/d from −0.142 to 0.142. Kt values less than 0.3 can be easily obtained for the case of Δ/d=+0.071 and 0.142, where Δ is the height of exposure (+ve) or depth of immersion (−ve) of the top tip of the vertical barrier. This breakwater is capable of dissipating wave energy to an extent of 50–80%. The overall performance of this breakwater was found to be better in the random wave fields than in the regular waves. A comparison of the hydrodynamic performance of ‘’-type and ‘T’-type shows that ‘T’-type breakwater is better than ‘’-type by about 20–30% under identical conditions.  相似文献   

3.
A logarithmic velocity profile is often fitted to velocity data in order to calculate the friction velocity (u *) and typify the surface texture by a roughness length (z o ). A method is given for estimating the errors in these parameters as calculated by this method. An example is given in which the size of the error is compared with the fluctuations that typically occur in the time seriesu *(t) andz o (t).  相似文献   

4.
Comparing single beam and multibeam echo sounder data where surveys overlap we find that: 95% of multibeam measurements are repeatable to within 0.47% of depth; older single beam data can be at least as accurate as multibeam; single beam and multibeam profiles show excellent agreement at full-wavelengths longer than 4 km; archival sounding errors are not Gaussian; 95% of archival soundings in the northwest Atlantic are accurate to within 1.6% of depth; the 95th percentile error is about five times greater in pre-1969 data than in post-1968 data; many of the largest errors are located over large seafloor slopes, where small navigation errors can lead to large depth errors. Our uncertainty model has the form σ 2 = a 2 + (bz)2 + (cs)2, where 2σ is approximately the 95th percentile error, z is the depth, s is the slope, and a, b, c are constants we determine separately for pre-1969 and post-1968 data.  相似文献   

5.
Displaying “calculated minus observed” data for precise titrations of seawater with strong acid permits direct evaluation of important parameters and detection of systematic errors.At least two data sets from the GEOSECS (Geochemical Ocean Sections) program fit an equilibrium model (which includes carbonate, borate, sulfate, silicate, fluoride, and phosphate) within the most stringent experimental error, less than 2 μmol kg−1. The effect of various parameters on the fit of calculated to observed values depends strongly on pH. Although standard potential E0, total alkalinity At, total carbonate Ct, and first acidity constant of carbon dioxide pK1 are nearly independent, and can be determined for each data set, other parameters are strongly correlated. Within such groups, all but one parameter must be determined from data other than the titration curve.Adding an acid-base pair to the theoretical model (e.g. Cx=20 μmol kg−1, pKx=6.2) produces a deviation approaching 20 μmol kg−1 at constant Ct; however, adjustment of Ct by about −18 μmol kg−1 to produce a good fit leaves only ± 1.5 μmol kg−1 residual deviation from the reference values. Thus, at current standards of precision, an unidentified weak acid cannot be distinguished from carbonate purely on the basis of the titration curve shape.There are few full sets of numerical data published, and most show larger systematic errors (3–12 μmol l−1) than the above; one well-defined source is experiments performed in unsealed vessels. Total carbonate can be explicitly obtained as a function of pH by a rearrangement of the titration curve equation; this can reveal a systematic decrease in Ct in the pH range 5–6, as a result of CO2 gas loss from the titration vessel. Attempts to compensate for this by adjustment of At, Ct, or pK1 produce deviations which mimic those produced by an additional acid-base pair.Changing from the free H+ scale (for which [HSO4−] and [HF] are explicit terms in the alkalinity) to the seawater scale (SWS) (where those terms are part of a constant factor multiplying [H+]) requires modification of the titration curve equation as well as adjustment of acidity constants. Even with this change, however, omission of pH-dependent terms in [HSO4−] and [HF] produces small systematic errors at low pH.Shifts in liquid junction potential also introduce small systematic errors, but are significant only at pH <3. High-pH errors due to response of the glass electrode to Na+ as well as H+ can be adequately compensated to pH 9.5 by a linear selectivity expression.  相似文献   

6.
A perturbation analysis is presented in which a series of small amplitude regular waves co-exist with an arbitrarily sheared current, U(z). Assuming that the current velocity is weak, i.e. U(z)/c=O(ε), the solution is extended to O(ε2), where c is the phase velocity and ε=ak the wave steepness. This provides a first approximation to the non-linear wave-current interaction, and allows simple explicit solutions for both the modified dispersion relation and the water-particle kinematics to be derived. These solutions differ from the existing irrotational models commonly used in design and, in particular, highlight the importance of the near-surface vorticity distribution. These results are shown to be in good agreement with laboratory data provided by Swan et. al. [J. Fluid Mech (2001, in press)]. Perhaps more surprisingly, good agreement is also achieved in a number of strongly non-linear wave-current combinations, where the results of the present analytical solution are compared with a fully non-linear numerical wave-current model.  相似文献   

7.
The optimum performance of a simple Rankine cycle ocean thermal energy conversion plant is investigated analytically. It is shown that the ratio of maximum net power output to heat exchanger surface area varies as H(Δt − t0)2 where H describes the overall heat transfer properties of the evaporator and condenser, Δt is the temperature difference between the warm and cold sea water supplies, and t0 is a parameter depending primarily upon the pressure drops across the warm and cold sea water pumping systems. The model is relatively insensitive to the choice of working fluid, although ammonia is used as the illustrative example.  相似文献   

8.
Association between weakening/strengthening of the eastward equatorial jet (EEJ) in both seasons and the Indian Ocean dipole (IOD) was investigated using two independent observational datasets (October 1992 to September 2007): (a) the dipole mode index I(t) and (b) the 5-day Ocean Surface Current Analyses-Realtime (OSCAR) obtained from satellite altimetry and scatterometer data, which has strong seasonal variability, with the EEJ occurrence in spring and fall, shown from the time-longitude cross-section of equatorial zonal velocity (1°S-1°N). The association is detected in two ways. First, time series of averaged zonal velocity over (1°S-1°N, 42°E-100°E) U(t) shows a close association to the dipole mode index: positive IOD events (1994, 1997, 2006) correspond to negative U (westward equatorial current), and negative IOD events (1994, 1995, 1999, 2005) correspond to positive U (eastward equatorial current). Second, the EEJ weakening/strengthening is represented by the streamfunction anomaly relative to its climatological monthly mean fields. The streamfunction anomaly is further analyzed using the empirical orthogonal function (EOF) method. The first EOF mode accounts for 55% of the variance with corresponding principal component A (1)(t) showing evident pattern of EEJ strengthening and weakening. The correlation coefficient between I(t) and A (1)(t) is around 0.49. This may confirm the linkage in some sense (only EOF-1 considered) between the positive (negative) IOD events and the weakening (strengthening) of the EEJ. The dipole pattern of lag-correlation between the sea surface temperature anomaly and U confirms the connection between the EEJ weakening/strengthening and the IOD events.  相似文献   

9.
We present a new approach that incorporates two models to estimate the underwater light field from remote sensing of ocean color. The first employs a series of analytical, semi-analytical, and empirical algorithms to retrieve the spectrum of inherent optical properties (IOPs), including the absorption and the backscatter coefficients, from the spectrum of remote sensing reflectance. The second model computes the profile of photosynthetically available radiation E 0,PAR (z) for a vertically homogeneous water column using the information of the retrieved IOPs and the ambient optical environment. This computation is based on an improved look-up table technology that possesses high accuracy, comparable with the full solution of the radiative transfer equation, and meets the computational requirement of remote sensing application. This new approach was validated by in situ measurements and an extensive model-to-model comparison with a wide range of IOPs. We successfully mapped the compensation depth by applying this new approach to process the SeaWiFS imagery. This research suggests that E 0,PAR (z) can be obtained routinely from ocean-color data and may have significant implications for the estimation of global heat and carbon budget.  相似文献   

10.
Growth of the red gurnard, Chelidonichthys kumu (Lesson and Garnot), from Pegasus Bay, Canterbury, was measured during 1966–67. Otoliths were used as an indicator of fish growth; mean length‐at‐age data were obtained from back‐calculated fish lengths at the time of formation of successive annual rings in the otoliths. Growth in length was found to be adequately expressed by the von Bertalanffy growth equation :

lt = 52.0 [1 ‐ e‐0.406 (t‐o.291)]

(where lt is the fork length in cm at age t). The length: weight relationship was:

w = 78.56 × 10‐4 l 3.072

(where w is the weight in grams). From this relationship, growth in weight was described by the equation:

wt = 1469 [1 ‐ e‐0.406 (t‐0.291)]3.  相似文献   

11.
Relationships between the surface concentrations of phytoplankton pigments (C ph), total suspended matter (C sm), particulate organic carbon (C poc), and total suspended phosphorus (C sp), on the one hand, and the relative water transparency determined through the Secchi disc depth (z d), on the other, are analysed using the data compiled in the Guinean coastal waters (Tabunsu and Tonkima river estuaries) during November–December 1990. The functions ofC ph,C sm=f(z d) are matched up with the experimentally derived data, as well as with the model bio-optical state of seawater. The general regression equation has been calculated using the data characteristic of various types of water.Translated by Vladimir A. Puchkin.  相似文献   

12.
Two models, a spectral refraction model (Longuet-Higgins) and a parabolic equation method (PEM) refraction-diffraction model (Kirby), are used to simulate the propagation of surface gravity waves across the Southern California Bight. The Bight contains numerous offshore islands and shoals and is significantly larger (≈ 300 km by 300 km) than regions typically studied with these models. The effects of complex bathymetry on the transformation of incident wave directional spectra, S0(f,θ0), which are very narrow in both frequency and direction are difficult to model accurately. As S0(f,θ0) becomes broader in both dimensions, agreement between the models improves and the spectra predicted at coastal sites become less sensitive to errors in the bathymetry grid, to tidal changes in the mean water depth, and to uncertainty in S0(f,θ0) itself. The smoothing associated with even relatively narrow (0.01 Hz-5° bandwidth) S0(f,θ0) is usually sufficient to bring the model predictions of shallow water energy into at least qualitative agreement. However, neither model is accurate at highly sheltered sites. The importance of diffraction degrades the predictions of the refraction model, and a positive bias [O (10%) of the deep ocean energy] in the refraction-diffraction model estimates, believed to stem from numerical “noise” (Kirby), may be comparable to the low wave energy. The best agreement between the predicted spectra generally occurs at moderately exposed locations in deeper waters within the Bight, away from shallow water diffractive effects and in the far-field of the islands. In these cases, the differences between the models are small, comparable to the errors caused by tidal fluctuations in water depth as waves propagate across the Bight. The accuracy of predicted energies at these sites is likely to be limited by the uncertainty in specifying S0(f,θ0).  相似文献   

13.
A logarithmic velocity profile is often fitted to velocity data in order to calculate the friction velocity (u *) and typify the surface texture by a roughness length (z o ). A method is given for estimating the errors in these parameters as calculated by this method. An example is given in which the size of the error is compared with the fluctuations that typically occur in the time seriesu *(t) andz o (t).  相似文献   

14.
We examined stable carbon and nitrogen isotopic signatures of 17 fish and 16 invertebrate taxa common to the Newfoundland and Labrador (NL) continental shelf food web. Particular sampling emphasis was placed on Atlantic cod (Gadus morhua) and related prey species (e.g. shrimp, Pandalus borealis, and capelin, Mallotus villosus). We found highly significant (p < 0.0001) differences between near-shore (bays) and offshore (shelf edge) δ15N signatures for cod, ‘other fish’ (pooled) and invertebrates (pooled). In contrast, there were only minor differences in δ13C signatures of ‘other fish’ (p < 0.05) and no difference for cod and invertebrates among the two habitats. We sampled at two times of the year (January and June) and found no systematic effect of season on both δ13C and δ15N in cod, ‘other fish’ and invertebrates. We calculated isotopic fractionation factors for cod from the entire shelf (mixed diet) and for cod with diets composed mainly of capelin or shrimp. These values ranged between 2.2‰ and 3.9‰ for δ15N and −0.4‰ and 0.8‰ for δ13C and, for δ15N, may reflect diet-related differences in bioenergetic status. We discuss potential mechanisms for near-shore versus offshore enrichment of δ15N signatures, and demonstrate the implications of this spatial variation on δ15N-derived trophic position estimates.  相似文献   

15.
Quasi-synoptic observations of the horizontal and vertical structure of a cold-core cyclonic mesoscale eddy feature (Cyclone Noah) were conducted in the lee of Hawai’i from November 4–22, 2004 as part of the E-Flux interdisciplinary collaborative research program. Cyclone Noah appears to have spun up to the southwest of the ‘Alenuihaha Channel (between Maui and Hawai’i) as a result of strong and persistent northeasterly trade winds through the channel. Shipboard hydrographic surveys 2.5 months later suggest that Noah weakened and was in a hypothesized spin-down phase of its life cycle. Although the initial surface expression of Noah was limited in scale to 40 km in diameter and, as evidenced by surface temperatures, 2–3 °C cooler than the surrounding waters, depth profiles revealed a fully developed semi-elliptical shallow feature (200 m), 144 km long and 90 km wide (based on sigma-t=23 kg m−3) with tangential speeds of 40–80 cm s−1, and substantial isopycnal doming. Potential vorticity distribution of Noah suggests that radial horizontal flow of the core water was inhibited from the surface to depths of 75 m, with high vorticity confined above the sigma-t=23.5 kg m−3 isopycnal surface. Upward displacements of isopycnal surfaces in the eddy's center (50 m) were congruent with enhanced pigment concentrations (0.50 mg m−3). Comparisons of the results obtained for E-Flux I (Noah) and E-Flux III (Opal) suggest that translation characteristics of cyclonic Hawaiian lee eddies may be important in establishing the biogeochemical and biological responses of the oligotrophic ocean to cyclonic eddies.  相似文献   

16.
Data on the diffusion coefficientK zand the concentration of H2S in the Black Sea are used to compute the depth distribution of the vertical flux, and the intensity of the H2S sources and sinks. On average, the total production of H2S in the Black Sea reaches 37×106 t/year. The main bulk of H2S is produced not at the bottom, but in the layer of 450–1300 m. Destruction of H2S prevails above the 400 m layer. Dissolved oxygen penetrating the H2S zone can oxidize only half of the hydrogen sulphide produced in the sea.Translated by Mikhail M. Trufanov.  相似文献   

17.
The present note deals with the exact analytical solution of thermal bending of clamped, anisotropic, elliptic plates in the case where the thermal field is given by an expression of the type T(x,y,z)=z(Ax2+Cxy+By2).The problem is of basic interest in some ocean and mechanical structural systems since anisotropic materials are commonly used in those fields. Obviously the case of an orthotropic material constitutes a particular situation of the problem under study.  相似文献   

18.
Fishery-dependent and fishery-independent distribution analyses together reveal four discrete areas of white stumpnose Rhabdosargus globiceps abundance between Port Nolloth and the Kei River off the Cape Province of South Africa: the Western Cape (Saldanha Bay), the South-Western Cape, the Southern Cape and the South-Eastern Cape. On the basis of migratory patterns determined from tagging and catch data, and on differences in growth rate and size-at-maturity, it is concluded that these areas of abundance represent four separate stocks. Each stock apparently disperses offshore in winter (to c. 130 m depth) and concentrates inshore (<60 m depth) in response to ocean ographic patterns during summer. Growth rate and size-at-50% maturity (L 50) increased clinally from the South-Eastern Cape through to the South-Western Cape, and in all three regions males matured at larger size than females. Sizes at maturity for male and female R. globiceps were respectively 18.6 and 15.3 cm (fork length, FL) in the South-Eastern Cape, 22.1 and 18.1 cm in the Southern Cape and 24.3 and 23.6 cm in the South-Western Cape. The fitted Von Bertalanffy growth equations for the three regions were: Lt = 349 (1?e?0.114(t+3.60)) mm for the South-Eastern Cape; Lt = 337 (1?e?0.207(t+1.05)) mm for the Southern Cape; and Lt = 379 (1?e?0.290(t+0.16)) mm for the South-Western Cape. Maximum ages recorded in each region were 21 years for the South-Western Cape, 20 years for the Southern Cape and 10 years for the South-Eastern Cape. Lack of older fish in the South-Eastern Cape sample, attributed to inadequate sample size, has probably resulted in overestimates of both L ∞ and K in this region. Spawning is from August to February, with a peak in spring (September–November). Early juvenile R. globiceps recruit into estuarine and surf-zone marine nursery areas at around 2–5cm (±3 months), but move progressively farther offshore with growth; those trawled deeper than 50 m east of Cape Agulhas were predominantly adults (20–35 cm FL). Because of cooler water temperatures west of Cape Agulhas, adults there are found from the surf zone to depths of only 20 m in summer.  相似文献   

19.
A total of 1125 specimens of sardine, Sardina pilchardus, ranging in total length from 4.9 to 12.5 cm (mean 8.31 ± 1.41 cm) and in weights between 1.02 g and 11.18 g (mean 4.40 ± 1.87 g) were randomly sampled using a beach seine from the Krka River estuary. Samples were collected monthly according to their occurrence in this area from October to February during 2002/03, 2003/04 and 2004/05, which is during the spawning period of this species. Monthly fluctuations in the length frequency distributions of sardine were observed during that time. The length–weight relationship of all sardine specimens was described by the equation: W=0.007L2.9587(r2 = 0.9626); and the isometric nature of relative growth was established (t = −5.1495; p < 0.05). According to the allometric condition factor Ka, sardine specimens were in better somatic condition at the beginning of their appearance (spawning period) in the Krka River estuary. The length at which 50% of sardines were mature (L50) was calculated to be 7.9 cm.  相似文献   

20.
Simple prediction methods are proposed to estimate the wave induced pressures on smooth impermeable seawalls. Based on the physics of the wave structure interaction, the sloped seawall is divided into a total of five zones (zones 1, 2 and 3 during run-up (corresponding pressures are called as positive pressures) and zones 4 and 5 during run-down (corresponding pressures are called negative pressures)) (Fig. 1). Zone 1 (0<z<d−Hi/2), where the wave pressure is governed by the partial reflection and phase shift; Zone 2 (d−Hi/2<z<d), where the effect of wave breaking and turbulence is significant; Zone 3 (d<z<Run-up height), where the pressure is induced by the run-up water; Zone 4 (Run-down<z<d), where the wave pressure is caused by the run-down effect and Zone 5 (0<z<d-Run down), where the negative wave pressures are due to partial reflection and phase shift effects. Here d is the water depth at the toe of the seawall, Hi is the incident wave height and z is the vertical elevation with toe of the seawall as origin and z is positive upward. For wave pressure prediction in zones 1 and 5, the empirical formula proposed by Ahrens et al. (1993) to estimate the wave reflection and Sutherland and Donoghue's recommendations (1998) for the estimation of phase shift of the waves caused by the sloped structures are used. Multiple regression analysis is carried out on the measured pressure data and empirical formulas are proposed for zones 2, 3 and 4. The recommendations of Van der Meer and Breteler (1990) and Schüttrumpf et al. (1994) for the prediction of wave run-down are used for pressure prediction at zone 4. Comparison of the proposed prediction formulas with the experimental results reveal that the prediction methods are good enough for practical purposes. The present study also shows a strong relation between wave reflection, wave run-up, wave run-down and phase shift of waves on wave pressures on the seawalls.  相似文献   

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