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1.
基于一维综合孔径微波辐射计的海面温度反演研究   总被引：1，自引：0，他引：1  
Due to the low spatial resolution of sea surface temperature(T_S) retrieval by real aperture microwave radiometers,in this study, an iterative retrieval method that minimizes the differences between brightness temperature(T_B)measured and modeled was used to retrieve sea surface temperature with a one-dimensional synthetic aperture microwave radiometer, temporarily named 1 D-SAMR. Regarding the configuration of the radiometer, an angular resolution of 0.43° was reached by theoretical calculation. Experiments on sea surface temperature retrieval were carried out with ideal parameters; the results show that the main factors affecting the retrieval accuracy of sea surface temperature are the accuracy of radiometer calibration and the precision of auxiliary geophysical parameters. In the case of no auxiliary parameter errors, the greatest error in retrieved sea surface temperature is obtained at low T_S scene(i.e., 0.710 6 K for the incidence angle of 35° under the radiometer calibration accuracy of0.5 K). While errors on auxiliary parameters are assumed to follow a Gaussian distribution, the greatest error on retrieved sea surface temperature was 1.330 5 K at an incidence angle of 65° in poorly known sea surface wind speed(W)(the error on W of 1.0 m/s) over high W scene, for the radiometer calibration accuracy of 0.5 K.  相似文献   

2.
Momentum and heat flux were measured with a sonic anemometer at the Marine Observation Tower in the port of ItÔ. Under unstable conditions (T w -T a =3C4C), using the eddy correlation method, results show thatCd=(1.2±0.3)×10–3 andCh=(1.5±0.3)×10–3 at 5.5 m above mean sea level except for the case of weak winds.An unexpected relationship betweenCd and (–z/L) was observed, that is,Cd decreases as (–z/L) increases. If roughness variation over the sea is taken into account, we can explain the decrease in the range of (–z/L) less than 1, but not in the range greater than 1. This is due to a strong instability effect and the change of roughness class, from moderately rough to smooth.  相似文献   

3.
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4.
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   

5.
Diurnal changes in seawater temperature affect the amount of air–sea gas exchange taking place through changes in solubility and buoyancy-driven nocturnal convection, which enhances the gas transfer velocity. We use a combination of in situ and satellite derived radiometric measurements and a modified version of the General Ocean Turbulence Model (GOTM), which includes the National Oceanic and Atmospheric Administration Coupled-Ocean Atmospheric Response Experiment (NOAA-COARE) air–sea gas transfer parameterization, to investigate heat and carbon dioxide exchange over the diurnal cycle in the Tropical Atlantic. A new term based on a water-side convective velocity scale (w*w) is included, to improve parameterization of convectively driven gas transfer. Meteorological data from the PIRATA mooring located at 10°S10°W in the Tropical Atlantic are used, in conjunction with cloud cover estimates from Meteosat-7, to calculate fluxes of longwave, latent and sensible heat along with a heat budget and temperature profiles during February 2002. Twin model experiments, representing idealistic and realistic conditions, reveal that over daily time scales the additional contribution to gas exchange from convective overturning is important. Increases in transfer velocity of up to 20% are observed during times of strong insolation and low wind speeds (<6 m s−1); the greatest enhancement from w*w to the CO2 flux occurs when diurnal warming is large. Hence, air–sea fluxes of CO2 calculated using simple parameterizations underestimate the contribution from convective processes. The results support the need for parameterizations of gas transfer that are based on more than wind speed alone and include information about the heat budget.  相似文献   

6.
It is known that there is a front-like structure at the mixed layer depth (MLD) distribution in the subtropical gyre, which is called the MLD front, and is associated with the formation region of mode water. In the present article, the generation mechanism of the MLD front is studied using an idealized ocean general circulation model with no seasonal forcing. First, it is shown that the MLD front occurs along a curve where u g ·∇T s = 0 is satisfied (u g is the upper ocean geostrophic velocity vector, T s is the sea surface temperature and ∇ is the horizontal gradient operator). In other words, the front is the boundary between the subduction region (u g ·∇T s > 0) and the region where subduction does not occur (u g ·∇T s < 0). Second, we have investigated subduction of low potential vorticity water at the MLD front, which has been pointed out by past studies. Since u g ·∇T s = 0 at the MLD front, the water particles do not cross the outcrop at the MLD front. The water that is subducted at the MLD front has come from the deep mixed layer region where the sea surface temperature is higher than that at the MLD front. The temperature of the water in the deep mixed layer region decreases as it is advected eastward, attains its minimum at the MLD front where u g ·∇T s = 0, and then subducts under the warmer surface layer. Since the deep mixed layer water subducts beneath a thin stratified surface layer, maintaining its thickness, the mixed layer depth changes abruptly at the subduction location.  相似文献   

7.
High resolution measurements of carbon dioxide and oxygen were made in surface waters of the central Arkona Sea (Baltic Sea) from May 2003 to September 2004. Sensors for CO2 partial pressure (pCO2w) and oxygen (O2) concentration were mounted in 7 m depth on a moored platform which is used for hydrographic and meteorological monitoring. The pCO2w data were obtained in half hour intervals and O2 was measured each hour as an average of a 10 min measurement. To check the performance of the sensors, pCO2w and O2 were determined by shipboard measurements on a research vessel which visited the site in 1–2 month intervals. In addition, pCO2w was measured on a “volunteer observing ship” (VOS) passing the platform each second day at a distance of about 25 km. Minima of 220 to 250 μatm of pCO2w were observed at the time of the spring bloom and a cyanobacteria bloom in mid-summer. During winter the pCO2w was mostly close to equilibrium with the atmosphere but maxima of 430 to 530 μatm were also observed. The seasonality of oxygen and pCO2w showed an opposing pattern. From a multiple regression analysis, we concluded that two processes primarily controlled pCO2w during our study: biological turnover and mixing. A parameterization, based on apparent oxygen utilisation (AOU) and salinity (S) only (pCO2w = 1.23 AOU + 43 S), reproduced the seasonality of pCO2w in surface water reasonably well. Based on our pCO2, salinity, and temperature data set, we attempted to separate processes changing total inorganic carbon concentrations (CT) by using an alkalinity–salinity relation for the area. The contribution of CO2 gas exchange and mixing were calculated and from this the biological turnover was deduced to reveal the calculated CT changes.The net annual uptake of CO2 in the central Arkona Sea was estimated to be about 1.5 Tg (1.5·1012 g) which was approximately balanced by a net oxygen release considering the uncertainties of the flux calculations. Near-coast CO2 emission due to episodic upwelling partly compensated the uptake of the central part of the Arkona Sea reducing the overall magnitude of the CO2 uptake.  相似文献   

8.
Current meter data from various depths near the sea bottom collected for 31 days at time intervals of 10 minutes using a subsurface buoy system at a depth at 38 m on the continental shelf off Akita, Japan have been analyzed. The results show the existence of a stationary Ekman layer. The typical range of the characteristic parameters are estimated as follows; friction velocity: 0.38 cm s–1; Ekman layer thickness: 16 m; logarithmic layer thickness: 4 m–6 m; constant flux layer thickness: 0.4–0.6 m; Ekman veering: 28.7°; drag coefficient: 0.24×10–2–0.53×10–2. Veering was also observed in the logarithmic layer.  相似文献   

9.
Measurements of bromoform (CHBr3), diiodomethane (CH2I2), chloroiodomethane (CH2ICl) and bromoiodomethane (CH2IBr) were made in the water column (5–100 m depth) of the Southern Ocean within 0–40 km of the Antarctic sea ice during the ANTXX1/2 transect of the German R/V Polarstern, at five locations between 70–72°S and 9–11°W in the Antarctic spring/summer of 2003–2004. Some of the profiles exhibited a very pronounced layer of surface sea-ice meltwater, as evidenced by salinity minima and temperature maxima, along with surface maxima in concentrations of CHBr3, CH2I2, CH2ICl and CH2IBr. These results are consistent with in situ surface halocarbon production by ice algae liberated from the sea ice, although production within the sea ice followed by transport cannot be entirely ruled out. Additional sub-surface maxima in halocarbons occurred between 20 and 80 m. At a station further from shore and not affected by surface sea-ice meltwater, surface concentrations of CH2I2 were decreased whereas CH2ICl concentrations were increased compared to the stations influenced by meltwater, consistent with photochemical conversion of CH2I2 to CH2ICl, perhaps during upward mixing from a layer at  70 m enhanced in iodocarbons. Mean surface (5–10 m) water concentrations of halocarbons in these coastal Antarctic waters were 57 pmol l− 1 CHBr3 (range 44–78 pmol l− 1), 4.2 pmol l− 1 CH2I2 (range 1.7–8.2 pmol l− 1), 0.8 pmol l− 1 CH2IBr (range 0.2–1.4 pmol l− 1), and 0.7 pmol l− 1 CH2ICl (range 0.2–2.4 pmol l− 1). Concurrent measurements in air suggested a sea-air flux of bromoform near the Antarctic coast of between 1 and 100 (mean 32.3, median 10.4) nmol m− 2 day− 1 and saturation anomalies of 557–1082% (mean 783%, median 733%), similar in magnitude to global shelf values. In surface samples affected by meltwater, CH2I2 fluxes ranged from 0.02 to 6.1 nmol m− 2 day− 1, with mean and median values of 1.9 and 1.1 nmol m− 2 day− 1, respectively.  相似文献   

10.
An accurate numerical prediction of the oceanic upper layer velocity is a demanding requirement for many applications at sea and is a function of several near-surface processes that need to be incorporated in a numerical model. Among them, we assess the effects of vertical resolution, different vertical mixing parameterization (the so-called Generic Length Scale –GLS– set of k–ε, k–ω, gen, and the Mellor–Yamada), and surface roughness values on turbulent kinetic energy (k) injection from breaking waves.First, we modified the GLS turbulence closure formulation in the Regional Ocean Modeling System (ROMS) to incorporate the surface flux of turbulent kinetic energy due to wave breaking. Then, we applied the model to idealized test cases, exploring the sensitivity to the above mentioned factors. Last, the model was applied to a realistic situation in the Adriatic Sea driven by numerical meteorological forcings and river discharges. In this case, numerical drifters were released during an intense episode of Bora winds that occurred in mid-February 2003, and their trajectories compared to the displacement of satellite-tracked drifters deployed during the ADRIA02-03 sea-truth campaign.Results indicted that the inclusion of the wave breaking process helps improve the accuracy of the numerical simulations, subject to an increase in the typical value of the surface roughness z0. Specifically, the best performance was obtained using αCH = 56,000 in the Charnok formula, the wave breaking parameterization activated, k–ε as the turbulence closure model. With these options, the relative error with respect to the average distance of the drifter was about 25% (5.5 km/day). The most sensitive factors in the model were found to be the value of αCH enhanced with respect to a standard value, followed by the adoption of wave breaking parameterization and the particular turbulence closure model selected.  相似文献   

11.
Estimation of the leeway drift of small craft   总被引：1，自引：0，他引：1  
Small craft (<6·4 m) leeway is determined as a function of the wind speed in the range of 5–20 knots (3·6–10·3 m/sec). Leeway is calculated relative to the surface current by measurement of the separation distance of the small craft from a dyed patch of surface water at sea, using time-sequenced aerial photography. Leeway increases linearly with wind speed for small craft equipped with or without a sea anchor in the wind range studied. Leeway for small craft without sea anchor can be calculated from the equation UL = 0.07 UW + 0.04 where UW is the wind speed at 2 m elevation. Leeway for small craft drifted off the be calculated from the equation ULD = 0·05 UW − 0·12. The small craft drifted off the downwind direction in about 80% of the experiments. The drift angle is variable and difficult to predict.  相似文献   

12.
Natural surface film experiments in inland waters and shallow offshore regions of the Baltic and Mediterranean Seas were carried out in the time period 1990–1999 under calm sea conditions using a novel device for sampling and force-area studies. The sampler-Langmuir trough-Wilhelmy filter paper plate system ‘cuts out’ an undisturbed film-covered sea area to perform π-A studies without any initial physico-chemical sample processing. The limiting specific area Alim (2.68–31.57 nm2/molecule) and mean molecular mass Mw (0.65–9.7 kDa) of microlayer surfactants were determined from the 2D virial equation of state applied to the isotherms. Enthalpy ΔH and entropy ΔSt of the 2D first-order phase transitions were evaluated using the Clausius-Clapeyron equation applied to the isotherms. Miscibility of film components and film structure evolution is expressed by the scaling exponent y adopting the 2D polymer film scaling theory. The stress-relaxation measurements revealed a two-step relaxation process at the interface with characteristic times τ1=1.1–2.8 and τ2=5.6–25.6 seconds suggesting the presence of diffusion-controlled and structural organisation relaxation phenomena. The obtained results suggest that natural films are a complex mixture of biomolecules covering a wide range of solubilities, surface activity and molecular masses with an apparent structural organisation exhibiting a spatial and temporal variability.  相似文献   

13.
Relations between sea-surface temperature (T s) and heat flux at the sea surface (F) have been investigated using data from ocean observation buoys located off Shikoku in the Sea of Japan and in the East China Sea. Wavelet transformation decomposed F and T s to wavelet coefficients (WLC) in the period-time domain. Assuming one-dimensional heat transfer by eddy diffusion in the upper ocean, the phase difference (δθ) defined as the difference between the phase of the temporal change rate of T s, and the phase of F ranges statistically from 0 to +π/4 when F changes T s, and is around −π/2 when heat convergence in the sea (Av) forces T s. The δθ values are distributed from 0 to +π/4 at one-day and one-year periods at all buoys. WLC amplitude (WLCA) of F at periods from 16 to 32 day periods, which may be caused by the atmospheric ridge-trough systems, maintains energy longer than WLCA at periods from 2 to 16 days, which may be caused by monsoonal surges. At periods from 2 to 64 days, δθ values distribute from 0 to +π/4 or around −π/2 at each event, reflecting the surroundings of each ocean, i.e., Kuroshio recirculation in the off-Shikoku area, water-temperature front in the Sea of Japan, and water exchange in the continental shelf edge in the East China Sea. We demonstrate that the wavelet analysis can characterize the correspondence between irregular signals of F and T s in various time scales and locations. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

14.
The chemical speciation of Cu and Zn was investigated by voltammetric titration methods in the surface waters (10 m) of the western Black Sea during an Istanbul–Sevastopol cruise conducted in November 1998. Supporting parameters (temperature (T), salinity (S), pH, alkalinity (Alk), suspended particulate matter (SPM) and dissolved and particulate 234Th) were obtained in order to distinguish hydrographic features against involvement of the metals in biogeochemical processes. In the Turkish continental slope region, the cruise track intersected a narrow vein of colder water originating on the western shelf. The core of this cold water vein was characterised by a relatively low salinity, higher specific alkalinity and higher metal (especially Cu) and metal-binding ligand concentrations.A very large portion of Cu (93–99.8%) and Zn (82–97%) was organically complexed. The degree of complexation was highest in shelf waters and lowest in the central gyre. Titration data for Cu were modelled by two classes of organic binding ligands characterised by (CL1=3–12 nM, log K1′=13.1–13.9) and (CL2=20–70 nM, log K2′=9.4–11.2). These ligands occurred mainly in the ‘dissolved’ phase, as defined by 0.4-μm filtration. The stronger Cu-binding ligand seemed to be produced in situ in response to Cu concentration, whereas the weaker Cu-binding ligand appeared to be derived from terrestrial sources and/or reducing shelf sediments. Titration results for Zn were generally represented by one class of ligands (CL1=8–23 nM, log K1′=9.4–10.2), which were almost uniformly distributed between the ‘dissolved’ (78±8%) and the particulate phase (22±8%). The concentration of these strong Zn-binding ligands showed a very good correlation with SPM (r2=0.64), which improved when the dissolved ligands alone were considered (r2=0.78). It is hypothesised that these ligands were produced in situ by the bacterial breakdown of particulate organic matter.  相似文献   

15.
An improved gas chromatographic system was constructed to analyze oceanic dissolved N2, Ar and O2 with a higher accuracy and shorter analytical time. To obtain a higher accuracy of N2, Ar and O2 measurements, the following was added to the system: (I) an air trapping system; (II) a N2–CO2 trapping system after the operation of the air trapping system; (III) an active carbon column system for separating N2 and CO2 completely and (IV) the introduction of automatic valves controlling most of the system. Compared to previous studies, the precision of the measurements of N2, Ar and O2 concentrations was higher at 0.04%, 0.05% and 0.02%, respectively, and our analytical time was shorter at 600 s. Using the improved analytical technique, concentrations of N2 (CN2, 561.69–611.81 μmol/kg) and Ar (CAr, 15.126–16.238 μmol/kg), saturation states of N2 (ΔN2, − 5.1–0.9%) and Ar (ΔAr, − 7.0 to − 1.1%) from 0 m to 3000 m depth in the western North Pacific were observed during March 2005. Based on these data, we propose a new concept for estimating the amount of bubble injection (B). The total error in calculating B was estimated to be about 20%. We estimated B from 12 to 43 μmol/kg in this region using the observational values of N2 and Ar. As each water mass had a significantly different value of B even with an error of 20%, it is possible to use it as an index of sea surface state for when each water mass is produced in the sea surface mixed layer. Moreover, based on our values of B, we estimated preformed dissolved oxygen (DO) (CpreDO, 309–332 μmol/kg) and the saturation state of CpreDO (ΔpreDO, − 7.0 to − 1.2%) in this region. Thus, the difference between CpreDO and DO content in the ocean interior may be a more useful index for biogenic organic decomposition in the ocean field compared to Apparent Oxygen Utilization (AOU). Until now, the estimation of oceanic uptake of anthropogenic CO2 has used AOU as a major parameter. Therefore, it may be necessary to re-evaluate the oceanic uptake of anthropogenic CO2 based on our new concept of B.  相似文献   

16.
A circular storm moves with a constant speedc along a geostrophic flow similar to a western boundary current in the upper layer of a two-layer ocean with the motionless lower layer. The linear inertia terms are retained. Effects of the current becomes more conspicuous for smallerc and insignificant forc above 10 m s–1. The inertia effects are manifested in cellular patterns of the interface perturbations with cell lengths of(c–vf –1 in a wake of the storm with a radius of an order of 100 km, wherev is the current velocity. On the left hand edge where the flow has a strong shear, the interface displacements have large amplitudes which increase with a distance along the path in a wake of the storm. These disturbances propagate to the left of the edge within an angle of cot–1 (c 2/gH0–1), whereg is the reduced gravity andH 0 is the depth of the interface at the edge of the current. Comparison with the observations during Typhoon Trix in 1971 south of Japan suggests that fluctuations of the daily mean sea level with several days' periods observed along the southern coast of Japan may be due to the stationary oscillations of the Kuroshio caused by the inertia undulations along its left edge or due to the propagating perturbations to the left.  相似文献   

17.
Resuspension, transport, and deposition of sediments over the continental shelf and slope are complex processes and there is still a need to understand the underlying spatial and temporal dynamical scales. As a step towards this goal, a two-dimensional slice model (zero gradients in the alongshore direction) based on the primitive flow equations and a range of sediment classes has been developed. The circulation is forced from rest by upwelling or downwelling winds, which are spatially uniform. Results are presented for a range of wind speeds and sediment settling speeds. Upwelling flows carry fine sediments (low settling speeds) far offshore within the surface Ekman layer, and significant deposition eventually occurs beyond the shelf break. However, coarser sediments quickly settle out of the deeper onshore component of the circulation, which can lead to accumulation of bottom sediments within the coastal zone. Downwelling flows are more effective at transporting coarse sediments off the shelf. However, strong vertical mixing at the shelf break ensures that some material is also carried into the surface Ekman layer and returned onshore. The concentrations and settling fluxes of coarse sediments decrease offshore and increase with depth under both upwelling and downwelling conditions, consistent with trends observed in sediment trap data. However, finer sediments decrease with depth (upwelling) or reach a maximum around the depth of the shelf break (downwelling). It is shown that under uniform wind conditions, suspended sediment concentrations and settling fluxes decay offshore over a length scale of order τs/ρf|ws|, where τs is the wind stress, ρ the water density, f the Coriolis parameter, and ws is the sediment settling velocity. This scaling applies to both upwelling and downwelling conditions, provided offshore transport is dominated by wind-driven advection, rather than horizontal diffusion.  相似文献   

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20.
-In this paper, an improvement and revision of the theory of Miiller (1974, 1976), has been made under two conditions: (1) the horizontal component of the Coriolis force has been taken into account in the equations of motion for the internal wave field; and (2) the role of internal waves with frequencies close to the inertial frequency has been considered. The values of the viscosity coefficients and the diffusivity coefficients obtained in this paper are: Theappearance of the cross-diffusion (vc) of momentum is a natural result from the effect of the horizontal Coriolis force. Therefore the role of the horizontal shear of the mean flow cannot be absolutely separated from that of the vertical shear. So far in testing Muller's theory, the approximation of effective wave stress obtained by Ruddick and Joyce (1979) was extensively used, but it has to be revised under the conditions of this paper. The revised approximation shows that the internal waves with low frequencies close to the inertial frequency pl  相似文献   

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