scholarly journals Tidal currents and Kuroshio transport variations in the Tokara Strait estimated from ferryboat ADCP data

2017 ◽  
Vol 122 (3) ◽  
pp. 2120-2142 ◽  
Author(s):  
Xiao-Hua Zhu ◽  
Hirohiko Nakamura ◽  
Menghong Dong ◽  
Ayako Nishina ◽  
Toru Yamashiro
Keyword(s):  
Tidal Currents ◽  
Tokara Strait ◽  
Adcp Data ◽  
Kuroshio Transport

Assimilation of Ship-Mounted ADCP Data for Barotropic Tides: Application to the Ross Sea

2005 ◽  
Vol 22 (6) ◽  
pp. 721-734 ◽  
Author(s):  
S. Y. Erofeeva ◽  
Laurie Padman ◽  
Gary Egbert
Keyword(s):  
Numerical Solutions ◽  
Ross Sea ◽  
Acoustic Doppler Current Profiler ◽  
Tidal Currents ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Current Profiler ◽  
Inverse Solutions ◽  
Adcp Data ◽  
Mean Circulation

Abstract The application of a generalized inverse approach for assimilating vessel-mounted acoustic Doppler current profiler (VM-ADCP) data into numerical solutions of barotropic tides is described. The derived estimates of tidal currents can be used to detide the VM-ADCP data and expose underlying mean circulation. The methodology is illustrated with data assimilation models of tidal currents in the Ross Sea. The prior solution, obtained by solving the nonlinear shallow-water equations by time stepping with a linear bottom friction parameterization and elevation of open boundary conditions obtained from a circum-Antarctic tide model, provides reasonably good fit to most available moored current meter data. Two inverse solutions were obtained: one assimilating moored current meter records and the other assimilating three cruises of VM-ADCP data. Fitting either the mooring time series or the VM-ADCP records leads to only small changes relative to the prior solution currents, except over the shelf break where short length scale, energetic diurnal topographic vorticity waves are present. It is shown that the dynamics embedded in the representer functions provides reasonable tidal corrections even with no prior information about forcing at open boundaries.

scholarly journals Tempo‐Spatial Variations of the Kuroshio Current in the Tokara Strait Based on Long‐Term Ferryboat ADCP Data

2019 ◽  
Vol 124 (8) ◽  
pp. 6030-6049 ◽  
Author(s):  
Zhao‐Jun Liu ◽  
Hirohiko Nakamura ◽  
Xiao‐Hua Zhu ◽  
Ayako Nishina ◽  
Xinyu Guo ◽  
...  
Keyword(s):  
Kuroshio Current ◽  
Spatial Variations ◽  
Tokara Strait ◽  
Adcp Data ◽  
The Kuroshio

scholarly journals Singular Spectrum Analysis of Nonstationary Tidal Currents Applied to ADCP Data from the Northeast Brazilian Shelf

2006 ◽  
Vol 23 (1) ◽  
pp. 138-151 ◽  
Author(s):  
Marcio L. Vianna ◽  
Viviane V. Menezes
Keyword(s):  
Time Series ◽  
Spectrum Analysis ◽  
Singular Spectrum Analysis ◽  
Tidal Currents ◽  
Shelf Area ◽  
Current Time ◽  
Singular Spectrum ◽  
Adcp Data ◽  
Tidal Constituents ◽  
Short Time

Abstract The development of new tools for the analysis of nonstationary currents, including tidal currents, has been the subject of recent research. In this work a method for studies of nonstationary barotropic or baroclinic currents based on empirical orthogonal function (EOF) and singular spectrum analysis (SSA) is proposed. It represents a new alternative to other methods of analysis of tidal currents in strong interaction with nontidal forcing, for example, the continuous wavelet transform. The advantage of the SSA method resides in the fact that it is fast, easy to implement, efficient for short-time records, and is based on the covariance structure of the data. If significant tidal constituents occur in the measurements, these are determined by the method itself even with short-time-series records. This is in contrast to the harmonic analysis (HA), where a large table of tidal constituents stated a priori are fitted to the data, even if the presence of some of these are spurious and not justified physically. The method is first demonstrated in the analysis of a synthetic current time series and then applied to an hourly current ADCP profile dataset of 410 days from the northeast Brazilian shelf. In both cases the SSA results were compared to the classical HA and the neoclassical short-term HA (STHA). The description of the shelf area where the ADCP was placed, the deployment and data acquisition operations, and the quality control data analysis are included for completeness. Analysis of the full ADCP quality-controlled data was done after a separation of the subtidal from the tidal high-frequency bands, although this traditional separation is not strictly necessary and was only made to better compare with HA and STHA. Analysis of the tidal band obtained from the ADCP data showed that the extracted tidal ellipse constituents present coherent oscillations dominated by the annual and 57-day periods, and changes in the sense of rotation of the current vector from anticyclonic to cyclonic in the ellipses. The subtidal band variability is shown to be also dominated by an annual and a 57-day period component, both polarized along the isobaths, which is suggestive of a nonlinear interaction of the subtidal and the tidal variability.

scholarly journals Detiding ADCP Data in a Highly Variable Shelf Sea: The Celtic Sea

2005 ◽  
Vol 22 (1) ◽  
pp. 84-97 ◽  
Author(s):  
L. Carrillo ◽  
A. J. Souza ◽  
A. E. Hill ◽  
J. Brown ◽  
L. Fernand ◽  
...  
Keyword(s):  
Least Squares ◽  
Least Squares Method ◽  
Three Dimensional ◽  
Acoustic Doppler Current Profiler ◽  
Tidal Currents ◽  
Shelf Area ◽  
Residual Currents ◽  
Current Profiler ◽  
Adcp Data ◽  
Celtic Sea

Abstract This paper presents a comparison of two conventional detiding techniques carried out for ship-mounted acoustic Doppler current profiler (ADCP) data collected in the European shelf area of the Celtic Sea during the summer of 1998. One technique consisted of extracting the vertically averaged tidal currents obtained from a barotropic three-dimensional numerical tidal model. The second technique consisted of fitting the spatiotemporal ADCP data using least squares and polynomial spatial functions. In the least squares technique, the incorporation of zero velocity normal to the coast appears to improve the estimation of the tidal currents near the coast. Quantitative comparisons of the results from both techniques with historical current meter observations are shown. However, both methods showed limitations in accurately representing the tidal currents in the study area. Consequently, an alternative detiding technique is proposed. This technique consists of blending the tidal currents derived from the numerical model with those fitted to the ADCP data from the least squares method. Improved results were obtained using the blending technique. ADCP-derived residual currents were comparable with contemporaneous flows measured using drifting buoys and also with estimates obtained by geostrophic calculations.

MAPPING TIDAL CURRENTS AND RESIDUAL CURRENTS BY USE OF COASTAL ACOUSTIC TOMOGRAPHY

2017 ◽  
Author(s):  
Xiao-Hua Zhu ◽  
Xiao-Hua Zhu ◽  
Ze-Nan Zhu ◽  
Ze-Nan Zhu ◽  
Xinyu Guo ◽  
...  
Keyword(s):  
Shallow Water ◽  
Shallow Water Equations ◽  
Mean Amplitude ◽  
Momentum Equation ◽  
Tidal Currents ◽  
Acoustic Tomography ◽  
Mean Values ◽  
Residual Currents ◽  
Water Depths ◽  
Deep Area

A coastal acoustic tomography (CAT) experiment for mapping the tidal currents in the Zhitouyang Bay was successfully carried out with seven acoustic stations during July 12 to 13, 2009. The horizontal distributions of tidal current in the tomography domain are calculated by the inverse analysis in which the travel time differences for sound traveling reciprocally are used as data. Spatial mean amplitude ratios M2 : M4 : M6 are 1.00 : 0.15 : 0.11. The shallow-water equations are used to analyze the generation mechanisms of M4 and M6. In the deep area, velocity amplitudes of M4 measured by CAT agree well with those of M4 predicted by the advection terms in the shallow water equations, indicating that M4 in the deep area where water depths are larger than 60 m is predominantly generated by the advection terms. M6 measured by CAT and M6 predicted by the nonlinear quadratic bottom friction terms agree well in the area where water depths are less than 20 m, indicating that friction mechanisms are predominant for generating M6 in the shallow area. Dynamic analysis of the residual currents using the tidally averaged momentum equation shows that spatial mean values of the horizontal pressure gradient due to residual sea level and of the advection of residual currents together contribute about 75% of the spatial mean values of the advection by the tidal currents, indicating that residual currents in this bay are induced mainly by the nonlinear effects of tidal currents.

Sign in / Sign up

Export Citation Format

Share Document