共查询到20条相似文献，搜索用时 31 毫秒
1.
Algorithm for HF radar vector current measurements 总被引：1，自引：0，他引：1
A new algorithm is proposed, called the stream function method (SFM) for producing vector current maps from radial data measured
by dual-site high frequency surface wave radar (HFSWR). In SFM, a scalar stream function is constructed under some oceanographic
assumptions. The function describes the two-dimensional (2-D) ocean surface water motion and is used to obtain the distribution
of vector currents. The performance of SFM is evaluated using simulated radial data, which demonstrates that SFM has advantages
over typical vectorial combination methods (VCM) both in error acceptance and robustness, and excels another method based
on least-squares fitting (LSF) in recovering the complicated current models. Furthermore, SFM is capable of providing the
total currents based on radials from single-site radar. We also test the assumptions of horizontal non-divergence in the simulation.
The new algorithm is applied to the field experiment data of Wuhan University’s ocean state measuring and analyzing radar
(OSMAR), collected in the coastal East China Sea during April 11–17, 2004. Quantitative comparisons are given between radar
results by three current algorithms and in-situ current meter measurements. Preliminary analysis of the vertical current shear is given based on the current meter measurements. 相似文献
2.
Shallow water depth retrieval from space-borne SAR imagery 总被引：1，自引：1，他引：0
Kaiguo Fan Weigen Huang Hui Lin Jiayi Pan Bin Fu Yanzhen Gu 《Journal of Oceanography》2011,67(4):405-413
Based on shallow water bathymetry synthetic aperture radar (SAR) imaging mechanism and the microwave scattering imaging model
for oceanic surface features, we developed a new method for shallow water depth retrieval from space-borne SAR images. The
first guess of surface currents and winds are estimated from the normalized radar crossing section (NRCS) profile of shallow
water bathymetry SAR imagery, according to the linear theory and geophysical model function. The NRCS profile is then simulated
by the microwave scattering imaging model. Both the surface currents and winds are adjusted by using the dichotomy method
step by step to make the M4S-simulated NRCS profiles approach those observed by SAR. Then, the surface currents and the wind
speeds are retrieved when a best fit between simulated signals and the SAR image appears. Finally, water depths are derived
using the Navier–Stokes equation and finite difference method with the best estimated currents and the surface winds. The
method is tested on two SAR images of the Taiwan Shoal. Results show that the simulated shallow water NRCS profile is in good
agreement with those measured by SAR with the correlation coefficient as high as 85%. In addition, when water depths retrieved
from the SAR image are compared with in situ measurements, both the root mean square and relative error are less than 3.0 m
and 6.5%, respectively, indicating that SAR images are useful for shallow water depth retrieval and suggesting that the proposed
method in this paper is convergent and applicable. 相似文献
3.
On the basis of the data of field measurements, we present the results of numerical analysis of the intensity of vertical
turbulent exchange in stratified layers of the Black Sea in the region of the shelf–continental-slope boundary depending on
the local stratification. The experiments were carried out within the framework of the GEF/BSERP and Black Sea-2004 international projects. The data were obtained by using a probing version of the Sigma-1 measuring complex. In processing the data of measurements, we apply a procedure of evaluation of the coefficient of vertical
turbulent diffusion depending on the external conditions based on the analysis of the spectra of the gradient of temperature
fluctuations. For the two studied regions of the shelf, the coefficients of turbulent exchange turn out to be much higher
(by about an order of magnitude) than for the open sea under similar conditions. This can be explained by the specific features
of the bottom topography affecting the dynamics of quasiinertial waves playing to role of the main causes of small-scale mixing
and vertical diffusion.
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 14–24, November–December, 2008. 相似文献
4.
V. V. Knysh G. K. Korotaev S. G. Demyshev V. N. Belokopytov 《Physical Oceanography》2005,15(3):142-160
We compare the thermohaline and dynamic characteristics of the Black Sea reconstructed by using two versions of climatic temperature
and salinity fields:old (1903–1982)and new (1903–2003). The fields are reconstructed with the help of continuous assimilation
of the climatic temperature and salinity in the model. It is shown that the climatic thermohaline fields constructed with
regard for the data of observations for the last 20 yr are characterized by an insignificant elevation of the halocline (pycnocline)in
the winter-spring period and the elevation of the upper boundary of the cold intermediate layer in the spring-summer period.
The intensity of surface geostrophic currents is greater than the same quantity computed on the basis of the old climatic
data for the whole year. The horizontal currents in the sea computed according to the new climatic data are more intense.
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Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 11–30, May–June, 2005. 相似文献
5.
The Princeton Ocean Model is adapted to the water area of the Balaklava Bay for the numerical analysis of circulation. The
calculations are performed with the help of the diagnostic method by using the data of the hydrological survey carried out
in the bay in August 1992. We study the structure of the surface and bottom currents in the analyzed period as well as the
vertical circulation of waters and the circulation averaged over the depth. The obtained three-dimensional fields of currents
are used for the numerical analysis of the process of propagation of passive contaminating impurities from the sources located
on the coasts of the Balaklava Bay.
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Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 49–61, May–June, 2005. 相似文献
6.
The results of shipboard measurements of the modulation characteristics of 3.2 cm radar signals scattered by a rough sea surface
at low grazing angles are reported. The experiments were carried out from on-board a drifting research vessel in the Atlantic
trade wind zone at wind speeds of 7–10 m s−1 and coinciding directions of the wind and waves. Azimuthal isotropy of the modulation spectra was observed. It is emphasized
that the ‘sea surface-scattered signal’ modified modulation transfer function is somewhat larger for horizontal polarization
than for vertical polarization.
Translated by V. Puchkin. 相似文献
7.
We analyze the seasonal variability of the climatic hydrophysical fields of the Black Sea reporduced in three numerical experiments
carried out according to the model of circulation. The numerical predictions are performed for a period of 12.5 yr on the
basis of the hydrological data accumulated in 1983–1995. The monthly average climatic fields of the current speed are reconstructed
according to the data on the climatic fields of temperature and salinity by the method of hydrodynamic adaptation (standard).
It is shown that, in prognostic calculations, the seasonal variability of temperature and salinity is qualitatively close
to the “standard” dependence. At the same time, the quantitative difference between the climatic behavior of the model and
the standard dependence may be significant. The annual cycle of the currents is characterized by the intensification of the
Main Black-Sea Current in winter. The structure of the hydrophysical fields of the sea in the model becomes much more realistic
if it is based on the actual hydrological data.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
8.
Yu. B. Ratner A. P. Tolstosheev A. L. Kholod S. V. Motyzhev 《Physical Oceanography》2009,19(3):170-185
We consider some specific features of creation of the database according to the results of drifter experiments carried out
in the Black Sea in 2001–2006. The general statistical information on all buoy studies in the sea is presented. The criteria
used to filter the primary data are suggested. The principles of formation and structuring of the drifter database are presented.
As an example, we describe the procedure and the results of comparison of model estimates with the data of contact measurements
of the sea-surface temperature by drifting buoys. 相似文献
9.
We perform the experimental verification of the applicability of the theory of similarity to the wave boundary layer and the
assessment of wave-induced perturbations of the air flow depending on various conditions of stratification of the atmosphere
and the state of the sea. The measurements were carried out from a stationary platform located in the coastal part of the
Black Sea. The experimental procedure is based on the simultaneous measurements of the profile and fluctuations of the wind
speed at 5–6 levels in the 1.3–21-m layer, the elevations of the sea surface, the directions of waves and winds, and the mean
gradients of temperature and humidity of air. The structure of the boundary layer in the region of measurements depends on
the direction of the wind. For weak and moderate onshore winds (< 9 m/sec), the approximate balance is preserved between the
production and dissipation of turbulent energy in the cases of unstable and neutral stratification. On the average, the estimates
of friction velocity according to the profiles are higher than the dissipative estimates by 10% mainly due to the deficiency
of dissipation near the surface. For the offshore wind, the structure of the boundary layer abruptly changes and is determined
not by the local parameters but by strong turbulent eddies formed over the dry land. The intensity of low-frequency turbulent
fluctuations and the gradient of wind velocity near the surface in the coastal zone are 1.5–2 times higher than for the open
sea.
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Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 42–61, May–June, 2007. 相似文献
10.
I. I. Karpatovich 《Physical Oceanography》2006,16(4):247-255
We consider a quasigeostrophic spectral model used for the prediction of synoptic currents in the barotropic ocean. The spectral
method is based on the expansion of the current function in a double series in cosines. An algorithm of numerical evaluation
of the nonlinear term in the equation of potential eddy is described in detail.
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Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 62–69, July–August, 2006. 相似文献
11.
Yu. V. Artamonov 《Physical Oceanography》2006,16(3):177-187
The monthly average values of the anomalies of the ocean level (according to the satellite data for 1992–2002) and the annual
average dynamic heights (hydrological data) are used to compute the seasonal cycle of geostrophic currents on the surface
of the Atlantic Ocean. It is shown that the west and east currents are intensified with a phase difference of several months.
At the same time, their latitudinal displacements are quasisynchronous. A delay of the seasonal signal in the east-west direction
of about 2–3 months (on the average) is typical of currents in the tropical zone of the Northern Hemisphere. On the contrary,
in the South Atlantic, the seasonal signal propagates in the west-east direction and its phase delay can be as large as almost
six months.
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Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 60–71, May–June, 2006. 相似文献
12.
Use of nautical radar as a wave monitoring instrument 总被引：2，自引：0，他引：2
Common marine X-Band radars can be used as a sensor to survey ocean wave fields. The wave field images provided by the radars are sampled and analysed by a wave monitoring system (called WaMoS II) developed by the German research institute GKSS. This measuring system can be mounted on a ship, on offshore stations or at coastal locations. The measurement is based on the backscatter of microwaves from the ocean surface, which is visible as ‘sea clutter' on the radar screen. From this observable sea clutter, a numerical analysis is carried out. The unambiguous directional wave spectrum, the surface currents and sea state parameters such as wave periods, wave lengths, and wave directions can be derived. To provide absolute wave heights, the response of the nautical radar must be calibrated. Similar to the wave height estimations for Synthetic Aperture Radars, the so-called ‘Signal to Noise Ratio' leads to the determination of the significant wave height (HS). In this paper, WaMoS II results are compared with directional buoy data to show the capabilities of nautical microwave radars for sea state measurements. 相似文献
13.
The seasonal climatic circulation of the sea reconstructed on the basis of assimilation of new arrays of many-year average
hydrological data in a model is analyzed. Five layers are discovered in the structure of climatic currents in the sea in depth:
the surface Ekman layer (∼ 10 m), a layer with small vertical gradients of the kinetic energy (∼ 10–60 m), a layer with relatively
high vertical gradients of the kinetic energy (∼ 60–150 m), a layer with gradual decrease in the kinetic energy and intensification
(from 250–350 m) of the east cyclonic gyre and Batumi anticyclonic eddy (∼ 150–1000 m), and an abyssal layer characterized
by an almost barotropic velocity (∼ 1000–2000 m). The specific features of the seasonal evolution of currents at these depths
are investigated. It is shown that the key role in the formation of deep-water circulation of the sea is played by the south
east flow, east cyclonic gyre, and Batumi anticyclonic eddy.
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Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 28–45, November–December, 2005. 相似文献
14.
V. G. Bondur Yu. V. Grebenyuk E. V. Ezhova V. I. Kazakov D. A. Sergeev I. A. Soustova Yu. I. Troitskaya 《Izvestiya Atmospheric and Oceanic Physics》2010,46(4):482-491
In a large test reservoir at the Institute of Applied Physics, Russian Academy of Sciences, a series of experiments were performed
to investigate the surface manifestations of internal waves radiated by a subsurface buoyant jet. The field of currents on
the water surface of the reservoir was studied through the distribution of temperature with shallow thermocline. Using Particle
Tracking Velocimetry (PTV), the velocity field of surface currents was measured. A theoretical model was developed to calculate
the rates of disturbances on the surface. A comparison with experimental data indicated that the calculated data of the surface
rate value are overestimated. This discrepancy was explained by the presence of a film of surface-active substances (SASs)
with experimentally obtained parameters. Using scale modeling coefficients, we estimated the parameters of internal waves
radiated by the subsurface wastewater system and the values of their surface manifestations in field conditions. We estimated
the hydrodynamic contrasts in the field of surface waves, which can be caused by these inhomogeneous currents on the surface.
For a wind velocity of 5 m/s, the magnitude of the contrast in the field of short waves can reach up to 10–25%, which is detected
with confidence by remote-sensing methods. 相似文献
15.
A. V. Polyakov Yu. M. Timofeyev A. B. Uspensky 《Izvestiya Atmospheric and Oceanic Physics》2011,47(9):1092-1096
Numerical experiments on the simultaneous retrieval of the temperature and spectral emissivity of different land types are
performed on the basis of inversion of the simulated high spectral resolution measurements by the IRFS-2 satellite IR sounder.
The IRFS-2 data inversion method is based on using a priori information on the spectral behavior of emissivity of different
land types and the multiple linear regression technique. The rms errors of determination of the underlying surface temperature
using different solving operators are 0.26–0.71 K. The application of the developed IRFS-2 measurement inversion method makes
it possible to estimate the land surface emissivity with an rms error not larger than 0.015. 相似文献
16.
On the basis of the satellite and ship data of many-year observations, we parametrize the albedo of the ocean-atmosphere system
both for the conditions of “fair weather” and for the maximum and climatic optical thicknesses of oceanic clouds. These results
are used to develop a procedure of practically exact reconstruction of the monthly average fluxes of integral solar radiation
and the radiation budget over the ice-free surface of the oceans according to the data of satellite measurements of albedo
(Nimbus NOAA satellite, 1974–1983) for arbitrary conditions of transparency of the atmosphere and cloudiness. We determine the current
and climatic monthly average values and the characteristics of interannual variability of all components of the radiation
mode of the ocean-atmosphere system with a spatial resolution of 500×500 km.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
17.
Ionometric measurements of the complexation degree of fluorides in seawater of 5–35‰ salinity at 25°C were carried out using
two procedures for the standardization of the measuring electrochemical circuits. It was shown that, if we determine the degree
of the fluorine complexation in seawater using the measured values of the total coefficients of the activity, the fraction
of free ions is much dependent on the value used of the activity coefficient of the free ions calculated by means of one of
the versions of either the second or third approximation of the Debye-Huckel electrostatic theory of strong electrolyte solutions.
With the more correct measurement of the fluorine complexation degree in seawater on the basis of the comparison of the EMF
values in pure KCl-KF solutions and in mixtures of these solutions and seawater at equal ionic power and fluoride concentrations,
a close correlation was revealed for the free ion fraction in three series of experiments at fluorine contents of 0.2, 0.3,
and 0.4 mM (the concentration of the fluorine in seawater of 35‰ salinity amounts to 0.421 ± 0.014 mM.) 相似文献
18.
In the coastal zone, as a result of mixing of waters, it is difficult to identify turbulent phenomena with a spatial scale
of 0.1–1 km accompanied by strong vertical flows according to the data of measuring temperature. On the basis of the data
of direct measurements, it is shown that turbulent structures are well pronounced in the field of breaking of wind waves.
We deduce empirical estimates of the response of the intensity of wave breaking to the magnitude of divergence of the current
and develop a theoretical model of the influence of inhomogeneities of currents on wave breaking capable of describing the
experimental data.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
19.
A. N. Solov’yev 《Oceanology》2010,50(6):909-914
The annual (2004–2006) series of probing using a multichannel filter-fluorimeter from the water’s surface to the bottom at
fixed sites in Kaliningrad Bay and the adjacent areas were carried out. The following parameters were recorded: the water
turbidity and temperature, the intensity of the fluorescence of the photosynthetic pigment (excitation at 450 nm, detection
band 675–820 nm), and the intensity of the background fluorescence of the dissolved organic matter. The high levels of “red
fluorescence” presumably related to the presence of photosynthetic bacterioplankton, live phytoplankton, or their mixture
(which demands further biological identification) annually registered in the aphotic zone of the water column represent specific
feature of the obtained data. 相似文献
20.
To study the long-term variability of the thermohaline and dynamic characteristics of the Black Sea, we use three versions
of climatic fields, namely, the fields reconstructed in the model according to the old (1903–1982) and new (1903–2003) hydrological
climatic data arrays of temperature and salinity and according to the data of satellite altimetry. The analysis of the altimetry-based
climatic fields confirms the distinctions (established earlier according to the old and new data arrays) in the seasonal variability
of the integral characteristics of temperature and salinity and in the structures of hydrophysical fields in the sea. It is
shown that, in the winter-spring season, the thermohaline fields reconstructed according to the new and altimetry data arrays
are characterized by a small elevation of the halocline (pycnocline) and the upper boundary of the cold intermediate layer.
In all seasons, the altimetry-based surface geostrophic currents contain numerous mesoscale eddies with different signs of
rotation. Moreover, in all seasons, the Rim Current reconstructed according to the altimetry data is characterized by a narrower
jet almost along the entire its length. This jet is especially intense near the coasts of West Anatolia.
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Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 3–17, July–August, 2006. 相似文献