Spherical harmonic coefficients of 10-day gravity field models
These are 10-day gravity field models from SH degree 2 up to SH degree and order 50, given every 10 days, using GRACE and LAGEOS data (in ITRF2000).
Models are provided every 10 days and are based solely on the 10 days (maximum) of data that are in this time interval (whereas « version 1 » models were provided every 10 days but were based on three consecutive 10-day periods with the weighting 0.5/1./0.5).
10-day models are stabilized towards EIGEN-GRGS.RL02.MEAN-FIELD , more precisely towards the realization of EIGEN-GRGS.RL02.MEAN-FIELD at each given epoch, with a new constraint law that depends on the degree and on the order of each coefficient (in version 1, the law was only degree-dependent and the models were constrained towards the static part of EIGEN-GL04S and later EIGEN-GL04C ).
It is reminded to the users of the GRGS products that NO SMOOTHING OR FILTERING is necessary when using them, since they have already been stabilized during their generation process.
There are some gaps in this time series, coming either from GPS, from accelerometers or from KBR data gaps. Twenty 10-day solutions are missing:
|Dates (yyyy-mm-dd)||Dates (yyyy-doy)||Julian days 1950|
Grids, images and movies
Grids, images and movies of geoid and equivalent water heights differences with static field are provided. The grids are 1° x 1° global grids of geoid height or equivalent water heights differences (in meters) between time-variable solutions and static field(at reference date if the static field includes time-variable terms). The images represent geoid or equivalent water heights differences (in millimeters) between time-variable solutions and static field (at reference date if the static field includes time-variable terms). Images are compiled in geoid or EWH movies.
The files provided here contain the so-called « dealiasing products » used by CNES/GRGS, temporally averaged in a manner consistent with the way the time-variable gravity field models are produced. In the processing of the GRACE data, the gravitational influence of the Earth atmospheric pressure on the satellites’ orbits, as well as the oceanic response to it, is taken into account in the form of ECMWF 3-D atmospheric pressure fields over the whole Earth every 6 hours (with linear interpolation in-between) and MOG2D model of the response of the oceanic domain to the atmospheric forcing (pressure and wind) at the same temporal resolution. A conversion from Pascal to normalized gravitational potential units is performed.
Reference paper : Bruinsma, S., Lemoine, J.-M., Biancale, R., et al: CNES/GRGS 10-day gravity field models (release 02) and their evaluation, Adv. Space Res., 45, 4, 587-601, 2010, doi: 10.1016/j.asr.2009.10.012.
Since 2009/08/31, a recomputed « XMASCEN » correction for the KBR-R measurement has been substituted for the one found in the Level-1B files. The « XMASCEN » correction accounts for the distance, along the measurement line of sight, between the KBR antenna phase centres and the satellites centres of mass. It depends on the satellites position, attitude and KBR antenna phase centre coordinates in the satellite reference frame. We have recomputed this correction, taking into account adjusted coordinates of the KBR antenna phase centres [Horwath et al., 2010], thus greatly reducing the horizontal striping at ~1000 km wavelength sometimes observed in the temporal solutions.
Reference paper : Horwath, M., Lemoine, J.-M., Biancale, R., Bourgogne, S.: Improved GRACE science results after adjustment of geometric biases in the Level-1B K-band ranging data, Journal of Geodesy, 2010/10/06, doi: 10.1007/s00190-010-0414-2. Read article.