共查询到20条相似文献，搜索用时 765 毫秒
1.
Correction method for full-depth current velocity with lowered acoustic Doppler current profiler (LADCP) 总被引：1，自引：0，他引：1
A new method is presented to process and correct full-depth current velocity data obtained from a lowered acoustic Doppler
current profiler (LADCP). The analysis shows that, except near the surface, the echo intensity of a reflected sound pulse
is closely correlated with the magnitude of the difference in vertical shear of velocity between downcast and upcast, indicating
an error in velocity shear. The present method features the use of echo intensity for the correction of velocity shear. The
correction values are determined as to fit LADCP velocity to shipboard ADCP (SADCP) and LADCP bottom-tracked velocities. The
method is as follows. Initially, a profile of velocity relative to the sea surface is obtained by integrating vertical shears
of velocity after low-quality data are rejected. Second, the relative velocity is fitted to the velocity at 100–800 dbar measured
by SADCP to obtain an “absolute” velocity profile. Third, the velocity shear is corrected using the relationship between the
errors in velocity shears and echo intensity, in order to adjust the velocity at sea bottom to the bottom-tracked velocity
measured by LADCP. Finally, the velocity profile is obtained from the SADCP-fitted velocity at depths less than 800 dbar and
the corrected velocity shear at depths greater than 800 dbar. This method is valid for a full-depth LADCP cast throughout
which the echo intensity is relatively high (greater than 75 dB in the present analysis). Although the processed velocity
may include errors of 1–2 cm s−1, this method produced qualitatively good current structures in the Northeast Pacific Basin that were consistent with the
deep current structures inferred from silicate distribution, and the averaged velocities were significantly different from
those calculated by the Visbeck (2002) method. 相似文献
2.
Nearly every spring since 1990, hydrographic data have been collected along a section in the Labrador Sea known as AR7W. Since 1995, lowered acoustic doppler current profiler (LADCP) data have also been collected. In this work we use data from six of these sections, spanning the time period 1995 through 2008, to determine absolute velocity across AR7W and analyze the main features of the general circulation in the area. We find that absolute velocity fields are characterized by strong, nearly barotropic flows all along the section, meaning there is no “level of no motion” for geostrophic velocity calculations. There is strong variability from year to year, especially in the strength of the boundary currents at each end; nevertheless, combining data from.all 6 sections yields a well-organized velocity field resembling that presented by Pickart and Spall (2007), except that our velocities tend to be stronger: there is a cyclonic boundary current system with offshore recirculations at both ends of the line; the interior is filled with virtually uniform, top-to-bottom bands of velocity with alternating signs. At the southwestern end of the section, the LADCP data reveal a dual core of the Labrador Current at times when horizontal resolution is adequate. At the northeastern end, the location of the recirculation offshore of the boundary current is bimodal, and hence the apparent width of the boundary current is bimodal as well. In the middle of the section, we have found a bottom current carrying overflow waters along the Northwest Atlantic Mid-Ocean Channel, suggesting one of various possible fast routes for those waters to reach the central Labrador Sea. We have used the hydrographic data to compute geostrophic velocities, referenced to the LADCP profiles, as well as to compute ocean heat transport across AR7W for four of our sections. For all but one year, these fluxes are comparable to the mean air–sea heat flux that occurs between AR7W and Davis Strait from December to May (O(50–80 TW)), and much larger than the annual average values (O(10–20 TW)). 相似文献
3.
V. V. Knysh G. K. Korotaev A. I. Mizyuk A. S. Sarkisyan 《Izvestiya Atmospheric and Oceanic Physics》2012,48(1):57-73
This paper considers the main steps in improving the methods for calculating the ocean (sea) dynamics on the basis of observational
data on sea-water temperature and salinity. The results of diagnostic and adaptation calculations for the near-equatorial
area of the West Atlantic in the area of the Lomonosov countercurrent formation are presented. We consider the problem of
the complex use of measurements of temperature, salinity, and current velocity in the POLYMODE polygons with their assimilation
into the model using a Kalman filter. The results of calculations of the coordinated fields with the mechanism of geostrophic
adaptation and using asynchronous measurements obtained by the Razrezy program are given. We discuss further modifications
of the assimilation algorithms for hydrological observation data in models of sea dynamics and the principles of adaptation
of hydrophysical fields that made it possible to reconstruct the climate fields of the Black Sea and to reproduce the basin
dynamics for 23 years. 相似文献
4.
On the basis of the results derived by theoretical analysis [1] and laboratory physical modelling [2] of the circulation seawater
and stratification, induced by buoyancy fluxes, the suggestion has been made that, possibly, the Black Sea currents system
is three-layered. It has been supposed that an anticyclonic current flows in the basin.
To verify this deduction, the data from MHI's archived dataset have been treated, and results from twoad hoc expeditions are submitted here. Analysis of the vertical structure of currents, based on thein situ velocity measurements, using various means and calculations of the geostrophic circulation, has confirmed that a flow with
the theoretically predicted parameters may exist in the Black Sea.
Translated by Vladimir A. Puchkin. 相似文献
5.
For the first time, an acoustic Doppler current profiler (ADCP) produced by the RDI is used in the water area of the Black
Sea in the lowered mode. This direction in the application of acoustic Doppler current profilers is now in the stage of development
and verification of various procedures of measurements with subsequent data processing and enables one to get the distributions
of current velocities down to depths of 1000–6000 m depending on the modification of the instrument. We describe the procedures
of measurements performed with the help of the ADCP in the lowered mode in the course of an expedition and the stages of processing
of the primary data based on the experience of application of similar acoustic current profilers at the Marine Hydrophysical
Institute of the Ukrainian National Academy of Sciences accumulated in the 1980s. We generalize the experience of application
of ADCP under the hydrological conditions of the Black Sea, propose the algorithms of data processing, present the profiles
of absolute current velocity at several stations, compare these profiles with the geostrophic velocities, and determine the
deep-water structure of the field of currents in a shelf-open-sea section made along 31.17°E.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 31–48, July–August, 2006. 相似文献
6.
We propose a method for the adaptive numerical analysis of current velocities in a basin including a shelf zone and having
a lengthy open boundary with the sea, at which the current velocity is not given. This method is based on a multilayer quasiisopycnic
model. We use an approach according to which one introduces additional terms of the source type into the equations of heat
and salt transfer and the equation of evolution of the thicknesses of layers. We describe the results of calculations of the
current velocities in the northwest part of the Black Sea in June on the basis of climatic data. We also analyse specific
features of thermohaline and dynamic structure of waters.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
7.
The measurements data provided by an antenna of distributed temperature sensors, mounted on an oceanographic tower in the
South Crimea continental shelf area, were applied to study the mechanism for the generation of short-period internal waves
with anomalous amplitudes in the Black Sea. For analysis, information was incorporated concerning the background hydrological
and meteorological conditions that were observed during the experiment. A mathematical model for the phenomenon under study
has been constructed, and calculations of the anomalous internal wave generation have been presented. The paper contains a
comparative analysis of thein situ data and simulation results, and demonstrates a good qualitative/quantitative agreement between the parameters of internal
waves.
Translated by Vladimir A. Puchkin. 相似文献
8.
Currents in the Drake Passage are studied using the data of a hydrographic section along the Shackleton Transverse Ridge observed in November 2007. The distribution of the velocity component normal to the section was computed by two methods: (a) directly on the basis of the lowered acoustic Doppler current profiler (LADCP) data; (b) by the calculation of geostrophic currents based on the CTD data with estimating the depth averaged velocity on the basis of the LADCP data. The main results of the research are the relatively low estimated value of the Antarctic Circumpolar Current (ACC) transport, which accounts for 65–70% of the ACC transports in December 2003 and November 2005, and the confirmation of the existence of several abyssal currents confined to the deep passages of the bottom topography. 相似文献
9.
The paper presents the results of an analysis of hydrological data obtained on cruise 89 of the R/V Professor Vodyanitskii from September 30 through October 19, 2016, in the central area of the northern Black Sea. Currents were measured using a lowered acoustic Doppler current profiler (LADCP) to a depth of 350 m. Examples of the current velocity profiles and conditional density at individual stations are presented. The averaged characteristics of the vertical current structure in the seasonal and permanent pycnoclines are discussed. The isopycnally averaged kinetic energy (KE) demonstrates an almost linear dependence on the conditional density (σθ). In the seasonal pycnocline, EK = 0.2–0.013σθ; in the permanent pycnocline, EK = 0.12–0.007σθ. An interpretation is given for the variability of the kinetic energy with depth. It is shown that the maxima of the averaged vertical shear profile correspond to the occurrence depth of the seasonal and permanent pycnoclines. The mean Richardson number has a value of ~10 in the upper sea layer and decreases with depth, assuming a value of ~3 at the 300 m horizon. The estimate for the vertical turbulent diffusion coefficient from the simplified model shows its increase with depth. 相似文献
10.
A. G. Zatsepin A. G. Ostrovskii V. V. Kremenetskiy S. S. Nizov V. B. Piotukh V. A. Soloviev D. A. Shvoev A. L. Tsibul’sky S. B. Kuklev O. N. Kukleva L. V. Moskalenko O. I. Podymov V. I. Baranov A. A. Kondrashov A. O. Korzh A. A. Kubryakov D. M. Soloviev S. V. Stanichny 《Izvestiya Atmospheric and Oceanic Physics》2014,50(1):13-25
The first data on the creation of the subsatellite polygon on the Black Sea shelf and continental slope in the Gelendzhik area (designed in order to permanently monitor the state of the aquatic environment and biota) and the plans for maintaining and developing this polygon are presented. The autonomous measuring systems of the polygon in the composition of bottom stations with acoustic Doppler current profilers (ADCP), Aqualog robotic profilers, and thermo-chains on moored buoy stations should make it possible to regularly obtain hydrophysical, hydrochemical, and bio-optical data with a high spatial-time resolution and transmit these data to the coastal center on a real-time basis. These field data should be used to study the characteristics and formation mechanisms of the marine environment and biota variability, as well as the water-exchange processes in the shelf-deep basin system, ocean-atmosphere coupling, and many other processes. These data are used to calibrate the satellite measurements and verify the water circulation numerical simulation. It is assumed to use these data in order to warn about the hazardous natural phenomena and control the marine environment state and its variation under the action of anthropogenic and natural factors, including climatic trends. It is planned to use the polygon subsatellite monitoring methods and equipment in other coastal areas, including other Black Sea sectors, in order to create a unified system for monitoring the Black Sea shelf-slope zone. 相似文献
11.
A. G. Zatsepin V. B. Piotouh A. O. Korzh O. N. Kukleva D. M. Soloviev 《Oceanology》2012,52(5):579-592
The results of long-term measurements (16 months) of the current??s velocity in the Black Sea coastal zone near Golubaya Bukhta (Blue Bay) by a bottom mounted acoustic Doppler current profiler (ADCP) are presented and discussed. It was found that the alongshore component of the current dominates and its absolute value is an order of magnitude larger than the absolute value of the normal to the shore component. The annual average value of the alongshore current??s velocity is close to zero. A well pronounced oscillatory mode of the alongshore current??s velocity is revealed. This mode is characterized by quasi-periodic changes in the direction of the alongshore current. The maximal amplitudes of the unidirectional alongshore current??s velocity are observed with a time scale from several hours to several days. 相似文献
12.
This paper discusses the quasi-stationary Black Sea rim current velocity field observed at seven points of the shelf area
and continental slope in the vicinity of South Crimea from 6 June to 15 July, 1991. Current velocity fluctuations conditioned
by the difference in atmospheric pressures over the eastern part of the sea and the western one, with the wind speed being
5 cm s−1, have been studied. Inertial and seiche flows are described numerically. The peculiarities of the kinematics of the Black
Sea rim current’s regular component have been scrutinized.
Translated by Vladimir A. Puchkin. 相似文献
13.
This paper discusses the possibility of measurement of the current velocity vector characteristics averaged over the time of continuous regular down-up probings from a moving carrier. The measurements can be carried out either from a moving vessel or from a helicopter, floating on or hovering above the sea surface. As an illustration for the suggested technique,in situ observations compiled by a free-component (±XYZ) VEGA-3 probe in the Guiana current region in March 1990 are provided. Comparison of the results with buoy data shows good agreement within the accuracy limits of the instruments employed.Translated by Vladimir A. Puchkin. 相似文献
14.
A. V. Garmashov A. A. Kubryakov M. V. Shokurov S. V. Stanichny Yu. N. Toloknov A. I. Korovushkin 《Izvestiya Atmospheric and Oceanic Physics》2016,52(3):309-316
Wind-velocity data obtained from in situ measurements at the Golitsyno-4 marine stationary platform have been compared with QuikSCAT scatterometer data; NCEP, MERRA, and ERA-Interim global reanalyses and MM5 regional atmospheric reanalysis. In order to adjust wind velocity measured at a height of 37 m above the sea surface to a standard height of 10 m with stratification taken into account, the Monin–Obukhov theory and regional atmospheric reanalysis data are used. Data obtained with the QuikSCAT scatterometer most adequately describe the real variability of wind over the Black Sea. Errors in reanalysis data are not high either: the regression coefficient varies from 0.98 to 1.06, the rms deviation of the velocity amplitude varies from 1.90 to 2.24 m/s, and the rms deviation of the direction angle varies from 26° to 36°. Errors in determining the velocity and direction of wind depend on its amplitude: under weak winds (<3 m/s), the velocity of wind is overestimated and errors significantly increase in determining its direction; under strong winds (>12 m/s), its velocity is underestimated. The influence of these errors on both spatial and temporal estimates of the characteristics of wind over the Black Sea is briefly considered. 相似文献
15.
We demonstrate the possibility of determination of the spectral characteristics of absorption and backward scattering of light
in the Black Sea according to the data of a SeaWiFS satellite device. We use specially selected data of observations obtained under favorable atmospheric conditions. It is shown
that the results of calculations performed by using different methods are almost identical and weakly depend on the model
parameters of the spectral course of the coefficients of absorption of light by yellow substance and its scattering by suspended
particles. 相似文献
16.
Forecasting of tsunami wave heights at the Russian coast of the Black Sea is discussed. Prognostic numerical calculations
of tsunamis were carried out for the tsunami sources uniformly distributed in the Black Sea basin (a total of 55 events).
Their results are compared with the results of numerical modeling of the historical events (in 1939 and 1966) and the data
of not numerous measurements. A preliminary forecast is made on this basis for the tsunami wave heights along the Russian
coast of the Black Sea. 相似文献
17.
18.
We analyze the statistical structure of the data of remote sensing of the fields of surface temperature and the concentration
of chlorophyll in the northwest part of the Black Sea with an aim to apply the method of optimal interpolation to the restoration
of the maps of these fields according to the restricted amounts of data. We determine the scales of smoothing for the selection
of the random components of the fields and estimate their difference from the statistical model uniform and isotropic over
the space correlation coefficients. The functions of spectral densities are constructed along various sections and the best
intervals of discretization of the fields required to perform the optimal interpolation with given accuracy are determined.
It is shown that the construction of the maps of fields under the conditions of controlled accuracy of reconstruction of their
values remains possible even if the amounts of the input satellite data are significantly decreased. We consider a procedure
of evaluation of the best possible amounts of data required for the use of the method of optimal interpolation. Some examples
of application of this procedure to the data of remote sensing of the fields of surface temperature and the concentration
of chlorophyll are presented. 相似文献
19.
A method of extracting wave parameters from surface displacement measured from a moving platform is presented. The article first presents a method for accurately measuring surface displacement using a single beam altimeter and heave sensor. A least squares approach is presented to estimate wave parameters using vessel velocity and perceived wave frequency that eliminates Doppler due to vessel motion. Two techniques for estimating wave frequency are presented: a block data method using MUSIC and a real-time method using demodulation. Sea trial results demonstrate that this method is as effective as a WaveRider buoy for estimating wave parameters. 相似文献
20.
We present a survey of the principles and methods of satellite monitoring of the ocean, analyze the prospects of application of the data of satellite measurements to the operative diagnostics and prediction of circulation in the Black Sea, and discuss the physical foundations of remote sensing, the possibilities of contemporary equipment aimed at the observation of the sea surface from satellites, and the applicability of satellites as retransmitters of the data of measurements from free-drifting buoys. The contemporary oceanographic investigations carried out from satellites enable one to use the accumulated data for the numerical analysis of currents in seas and oceans in the model of general circulation as well as for the creation of a system of operative diagnostics and prediction of the state of marine environment. Examples of experimental realization of elements of the system of operative diagnostics of the state of the Black Sea based on the use of the satellite data are presented and the prospects of prediction of currents in the basin are analyzed. 相似文献