On analysis and prediction of tides on the west coast of Great Britain |
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| Authors: | M Amin |
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| Institution: | Institute of Oceanographic Sciences, Bidston Observatory. Birkenhead, Merseyside L43 7RA |
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| Abstract: | Summary. Long-period tidal records from eight ports on the west coast of Great Britain are analysed, using both the harmonic method and the response function. Time series up to 9.5 yr were used so that fine structure of certain regions of high energy in the tidal residual spectrum may be examined. This also assisted in accurate separation of tides from surges. According to the currently accepted formulation of M1, its composition is not compatible with its actual composition in the real tide and, as such, has no useful purpose to serve in computation of predictions. Constituents Sa, Ssa, MA, and MB, are adversly affected by weather and long records are essential for their accurate separation. It has been observed that annual perturbations of S2, similar to those confirmed in recent years for M2, also exist but these are not readily recognisable because their speeds are the same as those of constituents T2 and R2. These perturbations, being highly sensitive to meteorological forces, are mainly responsible for cusps or humps in the vicinity of major tidal constituents in tidal residual spectra. The relationship of radiational and gravitational tides is found to be in very good agreement with theoretical results. In summer months non-predictable variance reduces to about half of the annual variance, reflecting the regional weather conditions of summer and winter. |
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