Academic literature on the topic 'Tidal Current Constituent Ellipse'

The tidal circulation in Paranagua Bay (Parana State, Southern Brazil) was studied based on the Princeton Ocean Model. The model domain covered the near shore region and the estuarine area, with about 1 km grid resolution in cross-shore and along-shore directions. Homogeneous and diagnostic distributions for temperature and salinity were used and 12 tidal constituents were considered to specify the elevations at the open boundaries. Tidal analysis of 29-days time series of elevations and currents for each grid point generated corange and cophase lines as well as the correspondent axes of the current ellipses for each constituent. These computed values reproduced well the observed amplifications and phase lags of surface elevations and currents. Residual flows show the formation of tidal eddies, related to coastal geometry and bottom topography.

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.

Abstract. The South China Sea (SCS) and the Java Sea (JS) are connected through the Karimata Strait, Gaspar Strait, and the southern Natuna Sea, where the tides are often used as open boundary condition for tidal simulation in the SCS or Indonesian seas. Tides, tidal currents, and tidal energy fluxes of the principle constituents K1, O1, Q1, M2, S2, and N2 at five stations in this area have been analyzed using in situ observational data. The results show that the diurnal tides are the dominant constituents in the entire study area. The constituent K1 has the largest amplitude, exceeding 50 cm, whereas the amplitudes of M2 are smaller than 5 cm at all stations. The amplitudes of S2 may exceed M2 in the Karimata and Gaspar straits. Tidal currents are mostly of rectilinear type in this area. The semi-major axes lengths of the diurnal tidal current ellipses are about 10 cm s−1, and those of the semidiurnal tidal currents are smaller than 5 cm s−1. The diurnal tidal energy flows from the SCS to the JS. The semidiurnal tidal energy flows from the SCS to the JS through the Karimata Strait and the eastern part of the southern Natuna Sea but flows in the opposite direction in the Gaspar Strait and the western part of the southern Natuna Sea. Harmonic analysis of sea level and current observation also suggest that the study area is located in the antinodal band of the diurnal tidal waves, and in the nodal band of the semidiurnal tidal waves. Comparisons show that the existing models are basically consistent with the observational results, but further improvements are necessary.

Abstract. The South China Sea (SCS) and the Java Sea (JS) are connected through the Karimata Strait, Gaspar Strait, and the southern Natuna Sea, where the tides are often used as open boundary condition for tidal simulation in the SCS or Indonesian seas. Tides, tidal currents and tidal energy fluxes of the principle constituents K1, O1, Q1, M2, S2 and N2 at five stations in this area have been analyzed using in-situ observational data. The results show that the diurnal tides are the dominant constituents in the entire study area. The constituent K1 has the largest amplitude, exceeding 50 cm, whereas the amplitudes of M2 are smaller than 5 cm at all stations. The amplitudes of S2 may exceed M2 in Karimata and Gaspar Straits. Tidal currents are mostly of rectilinear type in this area. The major semi axis lengths of the diurnal tidal current ellipses are about 10 cm s−1, and those of the semi-diurnal tidal currents are smaller than 5 cm s−1. The diurnal tidal energy flows from the SCS to the JS. The semi-diurnal tidal energy flows from the SCS to the JS through the Karimata Strait and the eastern part of the southern Natuna Sea but flows in the opposite direction in the Gaspar Strait and the western part of the southern Natuna Sea. Harmonic analysis of sea level and current observation also suggest that the study area is located in the loop band of the diurnal tidal waves, and in the nodal band of the semi-diurnal tidal waves. Comparisons show that the existing models are basically consistent with the observational results, but further improvements are necessary.