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SPOTL: Some Programs for Ocean-Tide Loading

  • Author(s): Agnew, Duncan Carr
  • et al.
Abstract

The increasing precision of geodetic measurements has made the effects of loading by ocean tides(or other sources) important to a wider range of researchers than just the earth-tide community.Computing such loading effects has, however, remained a rather specialized activity. This collectionof programs aims to make it easy to compute load tides, or, with slight modifications, the effects ofother loads.Given that the most accurate representations of the ocean tides require both global and regionalmodels, my aim has also been to make it easy to combine different tidal models, and to use differentEarth models (though the method is restricted to spherically symmetric ones). Especially for theglobal ocean tide there are many models available; this package provides a set of current modelsfound using different methods.The package also includes programs to allow the computed loads (or the ocean tide) to be convertedinto harmonic constants, and to compute the tide in the time domain from these constants. Forcompleteness a program for direct computation of the body tides is included; while its accuracy isnot as high as that of some others (for example Merriam (1992)), it should be more than adequatefor representing any but (perhaps) gravity-tide measurements with low-noise instruments.This package can actually be used to find the surface effects of any load, so long as these effects arefrom elastic deformation, which is appropriate for any load with a time constant shorter than years:for example, changing reservoir water levels, seasonal groundwater changes, and non-tidal oceanloading.

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