Service of the contribution to the geopotential due to atmosphere, land water storage and ocean



Contents:

Abstract

This page provides links to files relevant to the service of the atmospheric contribution to the geopotential provided by the International Mass Loading Service. The service provides time series of Stokes coefficients of the contribution of atmosphere, land water storage and the ocean to the geopotential into a series of spherical harmonics up to degree/order 64/64. The Stokes coefficients are updated within one hour of model update.

Introduction

Variations of the sureface pressure exerted by the atmosphere, land water storage and oceans causes changes in the Earth's gravity field. These changes should be taken in account for reduction of high precision observations.

Service of the contribution to geopotential cause by the atmosphere land water storage and the ocean

On 2005.01.24 the service of atmospheric contribution to geopotential was established.

The series of the Stokes coefficients of the harmonic expansion of the contribution of the atmosphere, land water storage, and the oceabn to the geopotential to degree/order 64/64 are computed.

Files to Download

Contribution to the geopotential caused by

Latency

See the current latency of the Mass Loading Service.

Method

The Stokes coefficient are obtained by expansion of the input pressure field into series of spherical harmonics. The Stokes coefficients are of this expansion are multiplied by a factor which depends on the load Love number of the certain degree. We used the load Love numbers derived by P. Gegeot on the basis of the preliminary Earth model (PREM) with of the surface pressure field. The loading Love numbers are expressed in the reference frame of the total Earth, i.e. the solid Earth and the atmosphere. Therefore degree 0 and degree 1 Stokes coefficients are zero.

NB: Harmonic variations at 20 frequencies, such as annual, semi-annual, diurnal, semi-dirunal, and otheres were evaluated using least sauares and removed from the surface pressure field. Therefore, the time series of the contribution to the geopotential does not contains harmonic terms

The Stokes coefficients using so called "4π normalization over the unit sphere". This means that the integral of the square of each spherical harmonics is 1/(4π).

Citation instruction

If you use this time series in your analysis, you are welcome to acknowledge in your publication that you used "the Stokes coefficients of the harmonic expansion of the contribution of the atmosphere to the geopotential provided by the International Mass Loading Service which are available on the Web at http://massloading/vgep (Petrov & Boy, 2005)".

References

  1. J.-P. Boy, L. Petrov, Memo on computing Stokes coefficients of the expansion of the atmosphere contribution to the geopotential into a series of spherical harmonics, Internal memo, unpublished, 2005. Available here.

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This page was prepared by Leonid Petrov ()
Last update: 2017.07.09_12:11:01