Tidal asymmetry in estuaries with mixed semidiurnal/diurnal tides
Nidzieko, Nicholas J.
MetadataShow full item record
Tidal asymmetry in estuaries with mixed, mainly semidiurnal tides arises from both the interaction of principal tides and the higher harmonics generated by distortions within the estuary. The duration asymmetry in rise and fall of water level caused by principal tides on the west coast of the continental United States is ebb-dominant, and so the tide entering estuaries is also ebb-dominant, prior to any internal distortions within the estuary. The interaction of higher harmonics with principal constituents either augments or cancels the duration asymmetry in the principal tides. In estuaries where tidal elevation and velocity phase are near quadrature (90° out of phase), the duration asymmetry in tidal elevation leads to asymmetries in tidal current magnitude. Asymmetry can be conveniently quantified in terms of the sample skewness, γ1, the normalized third sample moment about the mean. An analytic approximation to the skewness shows that traditional metrics of asymmetry, namely the ratio of constituent amplitudes and the relative constituent phase difference, arise from calculating the third sample moment. Observations from three California estuaries of different morphologies are presented as an illustration of how skewness can be used to quantify asymmetry in real systems. As in semidiurnal systems, morphology is a good predictor of whether higher harmonics engender ebb-dominance or flood-dominance, however asymmetry imposed by principal tides at the mouth must first be overcome and so there is a spatial evolution in the total asymmetry. Quantifying observations via skewness should be considered in addition to traditional metrics in estuaries with mixed tides.
Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 115 (2010): C08006, doi:10.1029/2009JC005864.
Showing items related by title, author, creator and subject.
The importance of tidal and lateral asymmetries in stratification to residual circulation in partially mixed estuaries Scully, Malcolm E.; Friedrichs, Carl T. (American Meteorological Society, 2007-06)Measurements collected in the York River estuary, Virginia, demonstrate the important impact that tidal and lateral asymmetries in turbulent mixing have on the tidally averaged residual circulation. A reduction in turbulent ...
Scully, Malcolm E.; Friedrichs, Carl T. (American Geophysical Union, 2007-07-28)Observations collected at two laterally adjacent locations are used to examine the processes driving sediment transport in the partially mixed York River Estuary. Estimates of sediment flux are decomposed into advective ...
Tidal asymmetry and residual circulation over linear sandbanks and their implication on sediment transport : a process-oriented numerical study Sanay, Rosario; Voulgaris, George; Warner, John C. (American Geophysical Union, 2007-12-22)A series of process-oriented numerical simulations is carried out in order to evaluate the relative role of locally generated residual flow and overtides on net sediment transport over linear sandbanks. The idealized ...