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.
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.
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.
Contribution to the geopotential caused by
- atmosphere:
| GEOS-FPIT |
Data range: [20000101_0000
,
20240418_2100
] UTC; |
Last update: 20240419_0317
UTC. |
Step 3 hours |
| MERRA2 |
Data range: [19800101_0000
,
20240301_1800
] UTC; |
Last update: 20240322_1905
UTC. |
Step 6 hours |
- land water storage:
| GEOS-FPIT |
Data range: [20000101_0030
,
20240418_1830
] UTC; |
Last update: 20240419_0318
UTC. |
Step 3 hours |
| MERRA2 |
Data range: [19800101_0000
,
20240301_2100
] UTC; |
Last update: 20240322_2113
UTC. |
Step 6 hours |
- non-tidal ocean:
| OMCT05 |
Data range: [unknown
,
unknown
] UTC; |
Last update: unknown
UTC. |
Step 6 hours |
See the current latency of the Mass Loading Service.
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
-
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.
Back to the International Mass Loading Service.
This page was prepared by Leonid Petrov
(
)
Last update: 2017.07.09_12:08:00