A Necessary Constraint on the Use of Extended Harmonic Analysis for Tide Predictions

When American and British tide researchers, in an effort to improve tide predictions for large-range shallow-water tides, greatly expanded the number of tide constituents (extended harmonic analysis), they chose the added frequencies by selecting peaks of energy greatly exceeding the continuum (noise level) in a high-resolution Fourier analysis of tide residuals (observed minus predicted). Unfortunately, some tide agencies are now routinely analyzing for a greatly expanded number of constituents without checking as to whether the amplitudes of these added constituents are significantly larger than the continuum. They do this believing that more is necessarily better; actually, in some cases, a future prediction may be worse unless this check is done routinely

The Evolution of Modern Tide Analysis and Prediction — Some Personal Memories

The science of tide analysis and prediction reached so high a level of achievement in the early years of this century that there was little change or improvement for about fifty years. However, as electronic computers became both available and more powerful, very significant changes were introduced into virtually all aspects of tide observation, analysis and prediction. By virtue of this author’s service for many years in the U.S. Coast and Geodetic Survey, the Atlantic Meteorological and Oceanographic Laboratories and, more recently, at Scripps Institution of Oceanography, he has been a participant in many aspects of the changed procedures. His memories of how these changes came about are featured in this paper

A harmonic method for predicting shallow-water tides

The development of an objective technique for identifying significant hidden frequencies in the spectrum makes it possible to accurately predict shallow-water tides by harmonic methods. For Anchorage, Alaska, the 114 constituents used include frequencies in every species (cycles per day) from 0 to 12. The larger set of constituents improved the predictions in times of high and low waters, range of tide, and shape of curve. The stationary characteristics of some of the added constituents have been tested with three years of Philadelphia data

The optimum wiggliness of tidal admittances

Some numerical experiments with recent offshore tide measurements have examined various parameters involved in tidal prediction by the response method: the number of prediction weights, their lead (and lag) times, and the treatment of radiational tides. The optimum number of weights depends directly on the length of record and inversely on noise level in a tidal band; more weights degrade the prediction and generate an artificial wiggliness in the admittance

The cross spectrum of sea level at San Francisco and Honolulu

Continuous series of tide records from 1905 to 1956 at San Francisco and Honolulu were reduced to smoothed values at 32-hour intervals. The cross spectrum of the resulting seri es was computed by the Tukey method for 750 narrow-frequency bands at intervals of 0.0005 cycles per day. The curves of spectral-energy density vary smoothly with frequency; the only significant peaks occur at tidal frequencies...

Travel Times of Seismic Sea Waves to Honolulu

again focused attention 'on the necessity for adequate protective measures against similar disasters in the future. The problem is obvi-ously complex, involving rapid loca,tion of the epicenter, the detection of the sea wave as it moves toward the Hawaiian Islands, a quick method of determining the time the wave will reach the islands, and finally an adequate means of providing security for people and property. The purpose of this study was the preparation of a chart of the Pacific Ocean which would show the travel time to Honolulu of a seismic sea wave from the plotted position of an earthquake epi-center (see Fig. 1, insert sheet). Given the time of the disturbance, the arrival time of the wave at Honolulu becomes immediately available. Oceanographers have long accepted the concept that the velocity of a seismic sea wave is a function of the depth of water and they have expressed it mathematically as v = Vgd, where v is the velocity of the wave, g the acceleration of gravity, and d the depth of the water. However, this formula for velocity has been considered by some authorities to be a rough approxima-tion; it was believed that the actual velocity would always be somewhat slower. The results of the computations made in the course of the study by Green (1946) created more confidence in the accuracy of travel times computed by means of this formula. These computations were not in-fluenced by the recorded arrival times; the times to several of the more distant place