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Marshall D. Earle

Abstract

A numerical wean surface wave model has been developed specifically to operate on desktop super micro-computers. The model uses one or more local and moving grids within which waves of importance at a location of interest are generated. Within these grids, processes of wave energy propagation, dissipation due to opposing winds, and generation by the wind are numerically performed using decoupled propagation numerical wave modeling techniques similar to those in several operational wave models which run on large computers. Swell is propagated accurately from generation areas to the location by great circle techniques. To enhance model use and computer efficiency, the model is general with arbitrary grid spacings, numbers of grid points, computational time steps, and wave energy frequency bands. Tests for three different meteorological situations (a strong frontal system, a major hurricane, and a severe extratropical storm) show that the same model can be used for many types of conditions of interest. The tests also show that the wave growth and dissipation algorithm, which are similar to those in other wave models, could be improved. Specific run times depend on model parameter values (grid spacing, number of grid points, time step, and number of frequency hands). For typical values, a real-time day of wave forecasting or hindcasting can be accomplished in one to ten minutes on available relatively low cost super microcomputers.

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Marshall D. Earle, Kathryn A. Bush, and Glenn D. Hamilton

Abstract

Unusally severe storms occurred in the northeast Pacific Ocean between January and March 1983, and waves from these storms caused extensive erosion and damage along the U.S. west coast. Wave conditions as measured by eight data buoys are described for an intense storm of northern California with significant wave heights up to 12.9 m that occurred during February 1983. A very uncommon feature of the wave spectra is considerable energy at long periods of 20 to 25 s. Long period waves were generated west of the northern buoys and propagated as high swell to the southern buoys. Swell propagation was consistent with classical wave theory. The ability to quantitatively identify high swell at northern buoys prior to its arrival at buoys off southern California may have real-time swell forecast applications. Differences between measurements and numerical wave model forecasts and hindcasts indicate the value of the wave data and areas where numerical modeling of such storm-generated waves could be improved.

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Mark F. Giardina, Marshall D. Earle, John C. Cranford, and Daniel A. Osiecki

Abstract

A low-cost tide gauge was developed and field tested to demonstrate a technology that would enable more cost-effective and greater sampling of spatially variable water levels and ocean surface waves. The gauge was designed to be adaptable to expendable and, possibly, air-deployed use for applications such as support of naval operations. The gauge incorporates a single printed circuit board that includes a very low power 3.3-Vdc microprocessor and 1 Mbyte of nonvolatile flash memory. A low-cost solid-state pressure sensor provides pressure data that are corrected automatically as a function of measured pressure and temperature and are processed within the gauge to provide low-frequency water levels and nondirectional surface wave information. Gauge-operating lifetimes range from more than four months to more than two years, depending on the data collection mode (tide or tide–wave) and the data collection interval (half-hourly or hourly). Gauge measurements are compared to measurements from a Sea-Bird Electronics, Inc., wave and tide gauge that uses a high quality quartz sensor.

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