GRACE GFZ RL05

The GFZ RL05 time-series is being released since March 17, 2012 and has replaced its precursor RL04 after the monthly solution for April 2012. At the time of writing (May 2013), GFZ RL05 solutions cover the time span from January 2003 till February 2013, including 117 monthly models and 494 weekly models, respectively. For the following months no models are available due to missing or anomalous L1B data: June 2003, January 2011, June 2011, May 2012, October 2012 and March 2013.

There have been no changes in information content compared to RL04, i.e. the RL05 models contain gravitational variations caused by hydrology, cryosphere, episodic events such as large earthquakes, glacial isostatic adjustment (GIA) and errors or unmodelled effects of the applied background models. A major difference w.r.t. RL04 is the fact that no rates for the spherical harmonic coefficients C20, C30, C40, C21 and S21 are included anymore, so users do not have to take care of applying any rates before analyzing the RL05 time-series (the reference epoch of each solution is the middle of the data span which has been used).  The maximum degree and order of the RL05 models has been reduced to 90x90 (RL04: 120x120).

For some dedicated months suffering from sparse ground track coverage caused by short-interval repeat orbit patterns (e.g. 4d-repeat peaked in 09/2004, 3d-repeat peaked in 05/2012), the solutions  are stabilized by applying a modified version of the regularization method used for previous releases, which is based on Kaula’s power law (Bettadpur, S (2004), GRACE Mission Status and Gravity Field Product Improvement Plans, Eos Trans. AGU, 85(47), Fall Meet. Suppl., Abstract G23A-01).

Compared to RL04, the current RL05 time-series shows improvements of about a factor of 2 in terms of noise reduction (i.e. less pronounced typical GRACE striping artefacts) and spatial resolution. The latter is displayed in the figure below, where cumulated degree variances of the models’ calibrated errors are shown. The level of mm-geoid accuracy has been improved from ~525km (RL04) to ~350km (RL05).

More details on RL05 can be found in the GFZ GRACE Level-2 Processing Standards Document for Level-2 Product Release 0005 or in the Release Notes for GFZ GRACE Level-2 Products - version RL05.

If any results based on the GFZ RL05 time series are published, users are kindly requested to cite the following reference:

Dahle, Christoph; Flechtner, Frank; Gruber, Christian; König, Daniel; König, Rolf; Michalak, Grzegorz; Neumayer, Karl-Hans (2012): GFZ GRACE Level-2 Processing Standards Document for Level-2 Product Release 0005, (Scientific Technical Report STR12/02 – Data, Revised Edition, January 2013), Potsdam, 21 p. DOI: 10.2312/GFZ.b103-1202-25