TUD-L2B-5dayEWH-GRACE

Novel GRACE-Only Level-2B gridded product

Welcome to the v1.0exp release of our 5-day resolution GRACE-derived dataset and its associated visualizations.

This collection contains experimental data products developed from GRACE K-band ranging (KBR) residual Level-1B (L1B), used in the gravity field recovery processing strategy.

These Level-2B products, gridded Equivalent Water Height (EWH), can be used for sub-monthly mass change studies.

Last update: 2025-04-25.

Directory Contents

Background & Overview

What are LGDs?

LGDs or Line-of-Sight Gravity Differences refer to the relative along-track component of the gravity difference vector between the GRACE(-FO) satellites.

Note: Throughout this site, LGDs refer to residual Line-of-Sight Gravity Differences, values after subtraction of background models.

From LGDs to EWH

Equivalent Water Heights are derived from the LGD grids using a yearly computed scaling and bias factors via linear regression:

EWH [cm] = S [cm/(nm/s²)] x LGD [nm/s²] + B [cm],

where S is the scaling factor and B is the bias.

Dataset in `TUD-L2B-5day/`

Product name: TUD-5d GRACE Level-2B LGD-derived product v1.0exp

TUD-L2B-5dayEWH_2002_2016.nc: NetCDF file of 5-day Equivalent Water Height from LGD
images/: Figures used in the dataset README documentation file.
plotting_tools/: Scripts to generate visualizations and summaries
quality_checks/: Images and report for validating the dataset integrity
requirements.txt: Python dependencies for plotting and analysis
LICENSE: two licenses for the dataset and provided plotting software
README.md: Documentation of dataset.

`TUD-L2B-5dayEWH_2002_2016.nc`

Variable name: “ewh_hf_lgd” - Equivalent Water Height estimates derived by regression in [cm].
Dimensions: lat, lon and time.
Time Range: January 2002 - August 2016
Grid cell size: 0.5 deg latitude x 0.5 deg longitude
Temporal Sampling: 5-day to sub-weekly

Files are separated by variable type and include metadata such as units, dimensions, and global attributes.

Plots and Figures

`lgd_visuals/`

Spatiotemporal visualization of LGDs via a GIF.
These LGDs were filtered within the frequency band: [0.9, 11] mHz which approximately coincides with the SH degrees [5, 62].

`ewh_visuals/`

Spatiotemporal visualization of the High-Frequency Level-2B product via a GIF.
plots/ contains a collection of global maps of the Level-2B product.

All plots are in .png format and named with corresponding year or region identifiers.

Future Work

We are already investigating improvements to generate version v2.0, with the focus being on:

investigating different gridding strategies,
exploring spatial filters to remove along-orbit non-gravitational artefacts present in the LGD solutions,
use of different time periods (sub-yearly) for the computation of scales and biases.
use of different GRACE-only Level-2 data (from CSR), and associated filters for the linear regression law,
improvements related to the LGD-EWH mapping itself.

Acknowledgments

This dataset is derived from:

Residual Level-1B (including pre-fit and post-fit) range-rate data has been provided by the Center for Space Research (CSR), Texas, USA. These data were derived from the RL06 processing strategy, up to spherical harmonic degree and order 180. DOI: https://doi.org/10.18738/T8/VY3U8L

Residual Level-1B data are classified as:

Pre-fit range-rate: Gravity retrieval input vector of reduced range-rate observations (from standard Level-1B).
Post-fit range-rate: Obtained after least-squares fitting: d = A. x, where A is the design matrix and x is the estimated parameter vector.
Geo-fit range-rate: Portion of the post-fit signal expressed only in terms of monthly Spherical Harmonic coefficients.
Post-fit residuals: The difference between pre-fits and post-fits, retaining sub-monthly geophysical gravity signals and unmodeled background model residuals (e.g., AOD1B RL06).

We thank CSR for providing us and making this data public. This research would not have been possible without it.

Citation

This dataset is experimental (v1.0exp). If used, please cite:

https://doi.org/10.4121/a685e7cf-1b84-4007-b206-89ae1c71dd6c.v1

`

References

Bettadpur, Srinivas; Save, Himanshu; Tapley, Byron; Nagel, Peter; Kang, Zhigui; Poole, Steven; Pie, Nadege; Ries, John, (2025). “CSR RL06 GRACE geofit and postfit dataset”, https://doi.org/10.18738/T8/VY3U8L, Texas Data Repository, V1.

Ghobadi-Far, K., Han, S.-C., Weller, S., Loomis, B. D., Luthcke, S. B., Mayer-Guerr, T., & Behzadpour, S. (2018).
A transfer function between line-of-sight gravity difference and GRACE intersatellite ranging data and an application to hydrological surface mass variation.
Journal of Geophysical Research: Solid Earth, 123, 9186-9201.
https://doi.org/10.1029/2018JB016088