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1.
《Ocean Modelling》2009,26(3-4):154-171
Ocean surface mixing and drift are influenced by the mixed layer depth, buoyancy fluxes and currents below the mixed layer. Drift and mixing are also functions of the surface Stokes drift Uss, volume Stokes transport TS, a wave breaking height scale Hswg, and the flux of energy from waves to ocean turbulence Φoc. Here we describe a global database of these parameters, estimated from a well-validated numerical wave model, that uses traditional forms of the wave generation and dissipation parameterizations, and covers the years 2003–2007. Compared to previous studies, the present work has the advantage of being consistent with the known physical processes that regulate the wave field and the air–sea fluxes, and also consistent with a very large number of in situ and satellite observations of wave parameters. Consequently, some of our estimates differ significantly from previous estimates. In particular, we find that the mean global integral of Φoc is 68 TW, and the yearly mean value of TS is typically 10–30% of the Ekman transport, except in well-defined regions where it can reach 60%. We also have refined our previous estimates of Uss by using a better treatment of the high frequency part of the wave spectrum. In the open ocean, Uss ≃ 0.013U10, where U10 is the wind speed at 10 m height. 相似文献
2.
粗糙海面L 和C 双波段的代价函数多参量遥感反演分析 总被引：1，自引：0，他引：1
利用代价函数(cost function)方法,通过分析粗糙海面L和C双波段多极化遥感亮温对海表盐度、温度、风速和有效波高等参数的敏感性以及L和C双波段多极化的代价函数收敛特性,建立了反演海表盐度、温度、风速和有效波高等多参数的L和C双波段多极化代价函数模式。双波段遥感模式分析结果表明:(1)对于双参数的联合反演,L和C双波段垂直极化代价函数联合反演海表盐度和温度可以获得较好的反演结果。(2)L波段垂直极化和C波段水平极化代价函数联合反演海表盐度和风速较好。(3)对于三参数联合反演,L波段垂直极化和C波段的双极化联合反演盐度、温度和风速的精度较高。(4)L波段亮温对有效波高的敏感性较低(C波段经验模式不含有效波高),使得有效波高反演误差较大,L和C波段经验模式不适合反演有效波高参数。另外,为了定量分析L和C双波段代价函数的多参量遥感反演结果,采用加性噪音模拟亮温方法,对上述L和C双波段多极化模式的盐度、温度和风速等多参数联合反演误差进行了分析,均得出较好的结果。结论表明L和C双波段代价函数联合反演多参量可以明显提高参量反演精度,为粗糙海表面多参量的反演提供了新的方法和途径。 相似文献
3.
Various wind velocitiesu
*,U
/2,U
andU
10 are correlated to the measured growth rate of water waves , whereu
* is the friction velocity of the wind, andU
/2,U
andU
10 are the wind speeds respectively at the heights /2, and 10m above sea surface (: wave length). It is shown that within a range of the dimensionless wind speed, 0.1<u
* /C<0.6, there are no appreciable differences in the correlations, whereC is the phase velocity of water waves. The present relation between andU
shows qualitatively similar properties as the one obtained by Al'Zanaidi and Hui (1984); the growth rate for waves with rough surface is larger than that with smooth surface. However, our present relations give, for the both waves with different surface roughness, larger values by factors 1.71.8 than those given by Al'Zanaidi and Hui's relation. 相似文献
4.
Changes from winter (July) to summer (February) in mixed layer carbon tracers and nutrients measured in the sub-Antarctic zone (SAZ), south of Australia, were used to derive a seasonal carbon budget. The region showed a strong winter to summer decrease in dissolved inorganic carbon (DIC; 45 µmol/kg) and fugacity of carbon dioxide (fCO2; 25 µatm), and an increase in stable carbon isotopic composition of DIC (δ13CDIC; 0.5‰), based on data collected between November 1997 and July 1999.The observed mixed layer changes are due to a combination of ocean mixing, air–sea exchange of CO2, and biological carbon production and export. After correction for mixing, we find that DIC decreases by up to 42 ± 3 µmol/kg from winter (July) to summer (February), with δ13CDIC enriched by up to 0.45 ± 0.05‰ for the same period. The enrichment of δ13CDIC between winter and summer is due to the preferential uptake of 12CO2 by marine phytoplankton during photosynthesis. Biological processes dominate the seasonal carbon budget (≈ 80%), while air–sea exchange of CO2 (≈ 10%) and mixing (≈ 10%) have smaller effects. We found the seasonal amplitude of fCO2 to be about half that of a study undertaken during 1991–1995 [Metzl, N., Tilbrook, B. and Poisson, A., 1999. The annual fCO2 cycle and the air–sea CO2 flux in the sub-Antarctic Ocean. Tellus Series B—Chemical and Physical Meteorology, 51(4): 849–861.] for the same region, indicating that SAZ may undergo significant inter-annual variations in surface fCO2. The seasonal DIC depletion implies a minimum biological carbon export of 3400 mmol C/ m2 from July to February. A comparison with nutrient changes indicates that organic carbon export occurs close to Redfield values (ΔP:ΔN:ΔC = 1:16:119). Extrapolating our estimates to the circumpolar sub-Antarctic Ocean implies a minimum organic carbon export of 0.65 GtC from the July to February period, about 5–7% of estimates of global export flux. Our estimate for biological carbon export is an order of magnitude greater than anthropogenic CO2 uptake in the same region and suggests that changes in biological export in the region may have large implications for future CO2 uptake by the ocean. 相似文献
5.
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
6.
Kuniaki Okuda 《Journal of Oceanography》1984,40(1):46-56
The minimum value of wind stress under which the flow velocity in short wind waves exceeds the phase speed is estimated by calculating the laminar boundary layer flow induced by the surface tangential stress with a dominant peak at the wave crest as observed in previous experiments. The minimum value of the wind stress is found to depend strongly on, the ratio of the flow velocity just below the boundary layer and the phase speed, but weakly onL, the wavelength. For wind waves previously studied (=0.5,L=10 cm), the excess flow appears when the air friction velocityu
* is larger than about 30 cm sec–1. The present results confirm that the excess flow found in my previous experiments is associated with the local growth of a laminar boundary layer flow near the wave crest. 相似文献
7.
Norihisa Imasato 《Journal of Oceanography》1976,32(6):253-266
The mechanism of the development of wind-waves will be proposed on the basis of the observed wave spectra in the wind tunnels and at Lake Biwa (Imasato, 1976). It consists of two aspects: One is that the air flow over the wind-waves transfers momentum concentratively to the steepest component waves and the other is that the upper limit of the growth of a wave spectral density is given by the ultimate value in the slope spectral density. The first aspect means that the wave field has the momentum transfer filter on receiving the momentum from the air flow. Wind-waves in the stage of sea-waves receive the necessary amount of momentum by the form drag,e.g. according to the Miles' (1960) inviscid mechanism, through a very narrow frequency region around a dominant spectral peak. On the other hand, wind-waves in the stage of initial-wavelets receive it according to the Miles' (1962a) viscous model through a fairly broad frequency region around the peak. The upper limit ofS
max
developing according to viscous mechanism is given byS
max
=6.40×10–4
k
max
–2cm2s andS
max
=2.03C(f
max
)–2cm2s(S
max
is the power density of the wave spectral peak with the frequencyf
max
,k
max
is the wave number corresponding to the frequencyf
max
andC is the phase velocity).From the second aspect, the upper limit of the growth of wave spectral density is given by 33.3f
–4cm2s in the frequency region of late stage of sea-waves. Therefore, the spectral peak, which has the largest value in the slope spectral density in the component waves of the wave spectrum, rises high over the line 4.15f
–5cm2s. The energy is transported from the spectral peak to the high frequency part and to the forward face of a wave spectrum by nonlinear wave-wave interaction. This nonlinearity is confirmed by the bispectra calculated from the observed wind-wave data. In the stage of sea-waves, nonlinear rearrangement of the wave energy comes from a narrow momentum transfer filter, and, in the stage of initial-wavelets, it comes mainly from small corrugations and small steepness of the wave field. 相似文献
8.
Yuichi Koike Yuzuru Nakaguchi Keizo Hiraki Terufumi Takeuchi Tomoyoshi Kokubo Takashi Ishimaru 《Journal of Oceanography》1993,49(6):641-656
A red tide due toGymnodinium nagasakiense was observed in August 1988 in Tanabe Bay, Wakayama Prefecture, Japan. The maximum cell concentration ofG. nagasakiense reached 1×105 cells ml–1 at the surface water. From May to September 1988, the following were monitored: water temperature, salinity, chlorophylla, D.O., dissolved nutrients (NO2–N, NO3–N, NH4–N, PO4–P DON, DOP), particulate nutrients (PON, POP) and three dissolved selenium species [Se(IV), Se(VI), Organic Se]. Dissolved inorganic nitrogen (NO3–N, NH4–N) decreased but PON, POP, DON, DOP and inorganic phosphate increased at the peak of the bloom. The concentration of organic selenium increased up to the bloom initiation period which started on 5 July, and then the concentration of Se(IV) increased as the concentration of organic selenium decreased at the peak of the bloom (3 August). The strong relationship was found between the concentration of Se(IV) and the cell concentration ofG. nagasakiense (r
2=0.98). The Se(IV) requirement ofG. nagasakiense was 2.89×10–17 moles cell–1, which was agreed well with 4.4×10–17 moles cell–1 found in a laboratory experiment onG. nagasakiense using selenium spiked artificial sea water medium. The average ratio of Se(IV) to dissolved inorganic nitrogen (DIN) during the red tide bloom was 11441, the ratio of Se(IV) to DIN at the surface with the maximum cell concentration ofG. nagasakiense of 1×105 cells ml–1 was 1137. These results suggested that selenium may play an important role in red tide outbreak ofG. nagasakiense. 相似文献
9.
Norihisa Imasato 《Journal of Oceanography》1976,32(1):21-32
The development process of wind-waves of which spectral peak distributes from 0.6 cps to 9.3 cps will be discussed on the basis of the wind tunnel experiments and of the field observations performed at Lake Biwa. The characteristics of power and slope spectra are here presented. The development process of these wind-waves is characterized by three stages;i.e. initial-wavelets, transition stage and sea-waves. In the wind tunnel experiments, the transition from the stage of the initial-wavelets to the transition stage occurs when the wave spectral peak arrives at the line 6.40×10–4
k
–2cm2·sec (wherek is wave number) or when the slope spectral density at the frequencyf
max becomes larger than 6.40×10–4 sec. In the stage of sea-waves, the component wave of a wave-spectral peak is steepest in the component waves. And the wave spectral peak develops along the line 1.02×102
f
–6 cm2·sec (wheref is the frequency corresponding to the wave numberk) untill it reaches the line 33.3f
–4cm2·sec, and thereafter develops along the latter line, which indicates the constant density of slope spectrum. It is suggested that the nonlinearity of wind-waves must become stronger as wind-waves develop. The effective momentum flux
ws
from the air flow to wind-waves in this stage is evaluated to be about 49% of the total stress
0. 相似文献
10.
Yutaka Nagata 《Journal of Oceanography》1978,34(5):204-216
Bispectral analysis is applied to records of the vertical profile of the vertical temperature gradient in the oceanic thermocline in the San Diego Trough. The bispectra exhibit three notable features; (1) bispectral peaks at the points (0.2 m–1, 0.2 m–1) and (0.2 m–1, 0.1 m–1), (2) bispectral ridges along the lines (
1=
0,
2=
0 and
1+
2=
0 corresponding to peak wavenumbers
0 in power spectra, and (3) array of bispectral peaks of interval of 0.2 m–1 The results are compared with the bispectra of several modeled time series of spike-array type. The periodicity of 5 m found in the records seems to have two meanings: spacing of predominant spikes and wavelength of predominant sinusoidal wave. If this indicates the existence of internal waves having a vertical wavelength the same as the scale of homogeneous layers, it would suggest the possible importance of internal waves in the formation and maintenance mechanisms of oceanic microstructure. 相似文献
11.
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
12.
The estimated characteristics of the atmospheric boundary layer, obtained by the simulation of wind wave fields using three versions of the WAM numerical model are compared with the well-known empirical dependences of drag coefficient C d on wind speed U 10 and wave age A, as well as with the dependence of dimensionless roughness height z n on inverse wave age u*/с р. Calculations carried out for several years in the areas of the Pacific and Indian oceans, based on the ERA-interim and CFSR wind reanalyses have shown good agreement between the model and empirical dependences C d (U 10) and C d (A). The range of estimated variability for z n (u*/с р ) has been found to be significantly less than empirical. It has been also found that estimated values of wind speed U 10W (t) are overestimated from 5 to 10% in all versions of WAM models compared with the input wind reanalysis U 10R (t) at the moments of appearance maximum values of wind U 10R (t). The reasons for the established features of the WAM model and their dependence on the model version are discussed. 相似文献
13.
The rates of the reduction of Cr(VI) with S(IV) were measured in deaerated NaCl solution as a function of pH, temperature and ionic strength. The rates of the reaction were found to be first order with respect to Cr(VI) and second order with respect to S(IV), in agreement with previous results obtained at concentrations two order higher than the present study. The reaction also showed a first-order dependence of the rates on the concentration of the proton and a small influence of temperature with an apparent energy of activation ΔHapp of 22.8 ± 3.4 kJ/mol. The rates were independent of ionic strength from 0.01 to 1 M. The rate of Cr(VI) reduction is described by the general expression
−d[Cr(VI)]/dt=k[Cr(VI)][S(IV)]2