Tidal ocean loading


Abstract

This page provides a summary of activities in modeling ocean loading in Goddard VLBI group

Introduction

The Earth as a whole responses to external forces as an elastic body. Tides in the ocean redistribute water mass with respect to land. Therefore, the weight of the column of water above the given point periodically changes. These changes may reach 40 mm vertical and 5 mm horizontal. Tidal ocean loading should be taken into account in reduction of astronomical and space geodesy observations when precision better than 5 nrad or 4 cm is required.

Results

Ocean tide can be characterized be a sum of harmonic constituents. For computing site displacements caused by tidal ocean loading a global ocean tidal maps for major harmonic constituents should be used. A tidal map represents the amplitude of the sea level due to harmonic constituent and the phase with respect of the astronomical tide. The global map is convolved with Green's functions which describes Earth's crust response on a loading of the point mass. I used software SPOTL developed by D. Agnew for computation of the displacements due to ocean loading. The following ocean tidal maps were used: In total, ocean loading for 26 frequencies is modeled.

Validation of the model

The model was extensively tested against the whole set of VLBI observations. More details can be found here.

Files for downloading

3-D displacements of VLBI stations caused by ocean loading.
File Format Size Comment
2003d_oclo.hps HARPOS
420 Kb This files is in the form suitable for reduction of observations. The plug-in interface to the Mark-4 VLBI analysis software Calc/Solve is provided.
2005f_oclo.hps HARPOS
1150 Kb This files is in the form suitable for reduction of observations. The plug-in interface to the Mark-4 VLBI analysis software Calc/Solve is provided.

Links

  1. Ocean tide loading provider (Hans-George Scherneck)

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Web page was prepared by Leonid Petrov ()
Last update: 20-JAN-2006 20:47:53