Global satellite gravity data products for prompt detection of short-term Mass Change (MC)

Tang, Miao; Han, Shin-Chan; Yuan, Linguo; Yeo, In-Young; Khaki, Mehdi; Papanikolaou, Thomas Loudis; Yang, Xinghai; Liu, Yifu; Jiang, Zhongshan

doi:10.5194/essd-2025-829

Preprints

https://doi.org/10.5194/essd-2025-829

Preprints

02 Feb 2026

| 02 Feb 2026

Status: a revised version of this preprint was accepted for the journal ESSD and is expected to appear here in due course.

Global satellite gravity data products for prompt detection of short-term Mass Change (MC)

Miao Tang, Shin-Chan Han, Linguo Yuan, In-Young Yeo, Mehdi Khaki, Thomas Loudis Papanikolaou, Xinghai Yang, Yifu Liu, and Zhongshan Jiang

Abstract. We present the globally available dataset of Line-of-sight Gravity Differences (LGD) as a new data product to fill the long-standing gap of investigating sub-monthly surface mass change from the satellite gravimetry along-track perspective. The dataset is generated directly from Gravity Recovery and Climate Experiment Follow-on (GRACE-FO) Level-1B intersatellite ranging observations, positioned conceptually between Level-1B measurements and Level-2 monthly gravity field solutions. Provided as along-track time series, LGD delivers instantaneous, in situ gravity change at satellite altitude, thus ensuring the fidelity of measurements by avoiding the complex preprocessing, regularization, and filtering applied to monthly products. The LGD dataset enables monitoring of sub-monthly terrestrial water storage variability and provides accurate information on timing and magnitude of water mass changes. GRACE-FO’s ground track allows LGD retrievals every 5–6 days in most low and mid latitude regions, while the revisit interval becomes shorter toward higher latitudes. Our LGD data products also contain climatology in the form of along-track gravity variations. We demonstrate its potential through case studies, including along-track diagnosis of flash drought evolution in the southeastern United States and the characterization of sub-monthly hydrological extremes in global hotspots. Results show that the LGD dataset resolves the critical timing (onset, peak, and termination) of hydrological extremes, which is unattainable from monthly products. The LGD dataset is available at https://doi.org/10.5281/zenodo.17766177 (Tang et al., 2025), which is expected to pave the way for advances in sub-monthly hydrological monitoring and can serve as a unique constraint for hydrological and geophysical models, opening new opportunities for Earth system sciences.

Received: 26 Dec 2025 – Discussion started: 02 Feb 2026

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.

Download & links

Miao Tang, Shin-Chan Han, Linguo Yuan, In-Young Yeo, Mehdi Khaki, Thomas Loudis Papanikolaou, Xinghai Yang, Yifu Liu, and Zhongshan Jiang

Status: closed

RC1:
'Comment on essd-2025-829', Anonymous Referee #1, 24 Mar 2026

Please find attached the file to see my review comments.
The article is subject to technical corrections, which are essential for correct reproducibility and completeness.

Citation: https://doi.org/10.5194/essd-2025-829-RC1
- AC1: 'Reply on RC1', Shin-Chan Han, 09 Jun 2026
  
  The comment was uploaded in the form of a supplement: https://essd.copernicus.org/preprints/essd-2025-829/essd-2025-829-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/essd-2025-829-AC1
CC1:
'Comment on essd-2025-829', Hong Li, 04 Jun 2026

Dear Authors,
I am very interested in the preprint entitled “Global satellite gravity data products for prompt detection of short-term Mass Change (MC)”. This work presents, for the first time in a systematic manner, a global dataset of Line-of-sight Gravity Differences (LGD) derived directly from GRACE-FO Level-1B observations, together with a detailed description of the generation methodology, data structure, and potential applications. I believe this study is of great scientific significance and practical value.
First, as an along-track instantaneous gravity observable, LGD breaks through the temporal resolution limitation of conventional GRACE/GRACE-FO monthly solutions (L2 or Mascon products). It captures surface mass variations at intervals of 5–6 days or even shorter, filling a long-standing gap in sub-monthly hydrological monitoring. More importantly, it paves the way for transitioning satellite gravimetry from pure scientific research towards operational applications, such as near-real-time early warning of flash droughts and rapid floods. The case studies presented (e.g., flash drought in the southeastern United States, sub-monthly changes in the Amazon and South Sudan) clearly demonstrate the unique advantage of the LGD dataset in resolving the onset, peak, and termination phases of hydrological extremes.
Second, since the transfer function method was introduced by Ghobadi-Far et al. (2018), LGD has gained broad interest in fields such as seismology, hydrology, and drought studies. However, the computation of LGD involves complex procedures including dynamic orbit integration, accelerometer calibration, and spectral transformation, which creates a high technical barrier for many potential users. The authors have done an outstanding job in processing the data with great care, making the entire workflow publicly available as a ready-to-use dataset. By downloading the published data, I found the data quality to be very high, with very few outliers, reflecting the authors’ rigorous data processing. Furthermore, the authors provide two additional functional LGD time series (L2-synthetic LGD and climatology-based LGD), which involve substantial extra work and offer users a rich set of product choices.
The paper also provides a clear and detailed description of the entire processing chain from L1B to LGD (reference orbit integration, range-rate residuals, range-acceleration residuals, transfer function, and band partitioning). The open-source code for forward-modeling LGD from L2 monthly solutions is also shared, ensuring good reproducibility.
While I strongly support this work, I would like to offer one minor technical suggestion. In Figure 5c, the LRI-LGD curves show noticeable high-frequency spikes (e.g., near the equator and between 30°N–0°N). Based on my understanding, these spikes are mainly caused by imperfect handling of phase jumps induced by attitude-control thruster firings in the JPL LRI1B RL04 product. If alternative LRI1B products from other institutions—such as HUST V01 (Huazhong University of Science and Technology), SYSU S10 (Sun Yat-sen University), or AEI V54 (Albert Einstein Institute)—are used, these thruster-induced artifacts can be further suppressed, thereby improving the signal-to-noise ratio of LRI-LGD in the frequency band around 20 mHz, albeit to a limited extent. The authors may consider evaluating the impact of different LRI1B products in a future update.
In addition, the current dataset only covers the GRACE-FO period (June 2018 – December 2024). Many long-term hydrological studies require a longer time series. I hope that the authors will process and release the LGD results for the GRACE mission (e.g., 2002–2017) as soon as possible. I believe this is not only my personal wish but also a common expectation among many potential users.
Overall, this dataset represents a major advance in satellite gravimetry, providing a valuable new tool for sub-monthly hydrological monitoring and Earth system science. Thank you again for the authors’ excellent work.
Sincerely,
HongLi

Citation: https://doi.org/10.5194/essd-2025-829-CC1
- AC2: 'Reply on CC1', Shin-Chan Han, 09 Jun 2026
  
  We sincerely thank Hong for the positive evaluation of our work, for carefully reviewing both the manuscript and the released dataset, and for recognizing the potential value of LGD for sub-monthly hydrological monitoring and Earth system science. We are particularly grateful for the encouraging comments regarding the quality of the dataset, the transparency of the processing workflow, and the effort devoted to making the data and code openly available.
  We also appreciate the valuable suggestion concerning alternative preprocessed LRI1B products. We agree that the use of improved LRI1B datasets, such as those developed by Huazhong University of Science and Technology, may further suppress residual artifacts related to phase jumps and attitude-control thruster firings, thereby leading to improved LRI-LGD quality and signal-to-noise ratio. We will carefully evaluate these products and consider incorporating them into future updates of the LGD dataset.
  We fully agree that a longer LGD record would greatly enhance the value of the dataset for long-term hydrological and climate studies. The generation and validation of GRACE-era LGD products are currently underway, and we will make every effort to release the corresponding GRACE LGD dataset as soon as possible in a future update.
  We thank you again for the constructive comments, encouragement, and strong support of this work.
  
  Citation: https://doi.org/10.5194/essd-2025-829-AC2
RC2:
'Comments on essd-2025-829', Guillaume Ramillien, 10 Jul 2026

Review of manuscript: "Global satellite gravity data products for prompt detection of short-term Mass Change"
July, 2026
GENERAL
The authors propose to recover surface water mass change from laser measurements data provided by the GRACE-FO mission and reduced for continental hydrology. This type of data ensures a better temporal resolution that enables to detect intra-month mass variations due to climatic events more accurately. Mapping of surface water mass is fast by considering the transfer function approach developed previously by Ghobadi-Far et al. (2018). The following discussion about the data frequency content and its exploitable bandwidth of the KBR and Laser Ranging Interferometry (LRI) related to surface spatial resolution remains very interesting, even if the question of improving the spatial resolution itself is much debatable due to remaining cross-track errors by considering the Ghobadi-Far et al. filtering, as it is shown numerically in the document. Moreover, the availability of these new type of LRI dataset is proposed and this would be really appreciated by research community. The quality of the presentation of this original work is very good and deserves to be published in ESSD once some minor corrections will be made (see my comments below).
MINOR CORRECTIONS
P.5. It would be simpler to explain that the raw along-track LRI observations are reduced in the GOCO6s software from known accelerations, including gravitational potential models listed in Table 1.
P.8. "using least-squares": is this a kind of 6-parameter least-square adjustment for each SH coefficient (constant term + linear trend + annual and semi-annual terms)? Please precise.
P.16. "20° of the equators": do you mean a 40° band of latitude centered on the Equator? Please precise.
P.20. "southeastern United States (SEUS)": "SouthEastern United States (SEUS)".
In all the document:
Please check the definition of acronyms, e.g. SEUS looks to be used in the text before being defined. Write "Line-O-Sight (LOS)" instaed of "line-of-sight (LOS)"
Text in the figures are sometimes too small, e.g. Figures 7 and 9. Please redraw them with larger text if necessary.
--- End of document ---

Citation: https://doi.org/10.5194/essd-2025-829-RC2
- AC3: 'Reply on RC2', Shin-Chan Han, 16 Jul 2026
  
  The comment was uploaded in the form of a supplement: https://essd.copernicus.org/preprints/essd-2025-829/essd-2025-829-AC3-supplement.pdf
  
  Citation: https://doi.org/10.5194/essd-2025-829-AC3

Status: closed

RC1:
'Comment on essd-2025-829', Anonymous Referee #1, 24 Mar 2026

Please find attached the file to see my review comments.
The article is subject to technical corrections, which are essential for correct reproducibility and completeness.

Citation: https://doi.org/10.5194/essd-2025-829-RC1
- AC1: 'Reply on RC1', Shin-Chan Han, 09 Jun 2026
  
  The comment was uploaded in the form of a supplement: https://essd.copernicus.org/preprints/essd-2025-829/essd-2025-829-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/essd-2025-829-AC1
CC1:
'Comment on essd-2025-829', Hong Li, 04 Jun 2026

Dear Authors,
I am very interested in the preprint entitled “Global satellite gravity data products for prompt detection of short-term Mass Change (MC)”. This work presents, for the first time in a systematic manner, a global dataset of Line-of-sight Gravity Differences (LGD) derived directly from GRACE-FO Level-1B observations, together with a detailed description of the generation methodology, data structure, and potential applications. I believe this study is of great scientific significance and practical value.
First, as an along-track instantaneous gravity observable, LGD breaks through the temporal resolution limitation of conventional GRACE/GRACE-FO monthly solutions (L2 or Mascon products). It captures surface mass variations at intervals of 5–6 days or even shorter, filling a long-standing gap in sub-monthly hydrological monitoring. More importantly, it paves the way for transitioning satellite gravimetry from pure scientific research towards operational applications, such as near-real-time early warning of flash droughts and rapid floods. The case studies presented (e.g., flash drought in the southeastern United States, sub-monthly changes in the Amazon and South Sudan) clearly demonstrate the unique advantage of the LGD dataset in resolving the onset, peak, and termination phases of hydrological extremes.
Second, since the transfer function method was introduced by Ghobadi-Far et al. (2018), LGD has gained broad interest in fields such as seismology, hydrology, and drought studies. However, the computation of LGD involves complex procedures including dynamic orbit integration, accelerometer calibration, and spectral transformation, which creates a high technical barrier for many potential users. The authors have done an outstanding job in processing the data with great care, making the entire workflow publicly available as a ready-to-use dataset. By downloading the published data, I found the data quality to be very high, with very few outliers, reflecting the authors’ rigorous data processing. Furthermore, the authors provide two additional functional LGD time series (L2-synthetic LGD and climatology-based LGD), which involve substantial extra work and offer users a rich set of product choices.
The paper also provides a clear and detailed description of the entire processing chain from L1B to LGD (reference orbit integration, range-rate residuals, range-acceleration residuals, transfer function, and band partitioning). The open-source code for forward-modeling LGD from L2 monthly solutions is also shared, ensuring good reproducibility.
While I strongly support this work, I would like to offer one minor technical suggestion. In Figure 5c, the LRI-LGD curves show noticeable high-frequency spikes (e.g., near the equator and between 30°N–0°N). Based on my understanding, these spikes are mainly caused by imperfect handling of phase jumps induced by attitude-control thruster firings in the JPL LRI1B RL04 product. If alternative LRI1B products from other institutions—such as HUST V01 (Huazhong University of Science and Technology), SYSU S10 (Sun Yat-sen University), or AEI V54 (Albert Einstein Institute)—are used, these thruster-induced artifacts can be further suppressed, thereby improving the signal-to-noise ratio of LRI-LGD in the frequency band around 20 mHz, albeit to a limited extent. The authors may consider evaluating the impact of different LRI1B products in a future update.
In addition, the current dataset only covers the GRACE-FO period (June 2018 – December 2024). Many long-term hydrological studies require a longer time series. I hope that the authors will process and release the LGD results for the GRACE mission (e.g., 2002–2017) as soon as possible. I believe this is not only my personal wish but also a common expectation among many potential users.
Overall, this dataset represents a major advance in satellite gravimetry, providing a valuable new tool for sub-monthly hydrological monitoring and Earth system science. Thank you again for the authors’ excellent work.
Sincerely,
HongLi

Citation: https://doi.org/10.5194/essd-2025-829-CC1
- AC2: 'Reply on CC1', Shin-Chan Han, 09 Jun 2026
  
  We sincerely thank Hong for the positive evaluation of our work, for carefully reviewing both the manuscript and the released dataset, and for recognizing the potential value of LGD for sub-monthly hydrological monitoring and Earth system science. We are particularly grateful for the encouraging comments regarding the quality of the dataset, the transparency of the processing workflow, and the effort devoted to making the data and code openly available.
  We also appreciate the valuable suggestion concerning alternative preprocessed LRI1B products. We agree that the use of improved LRI1B datasets, such as those developed by Huazhong University of Science and Technology, may further suppress residual artifacts related to phase jumps and attitude-control thruster firings, thereby leading to improved LRI-LGD quality and signal-to-noise ratio. We will carefully evaluate these products and consider incorporating them into future updates of the LGD dataset.
  We fully agree that a longer LGD record would greatly enhance the value of the dataset for long-term hydrological and climate studies. The generation and validation of GRACE-era LGD products are currently underway, and we will make every effort to release the corresponding GRACE LGD dataset as soon as possible in a future update.
  We thank you again for the constructive comments, encouragement, and strong support of this work.
  
  Citation: https://doi.org/10.5194/essd-2025-829-AC2
RC2:
'Comments on essd-2025-829', Guillaume Ramillien, 10 Jul 2026

Review of manuscript: "Global satellite gravity data products for prompt detection of short-term Mass Change"
July, 2026
GENERAL
The authors propose to recover surface water mass change from laser measurements data provided by the GRACE-FO mission and reduced for continental hydrology. This type of data ensures a better temporal resolution that enables to detect intra-month mass variations due to climatic events more accurately. Mapping of surface water mass is fast by considering the transfer function approach developed previously by Ghobadi-Far et al. (2018). The following discussion about the data frequency content and its exploitable bandwidth of the KBR and Laser Ranging Interferometry (LRI) related to surface spatial resolution remains very interesting, even if the question of improving the spatial resolution itself is much debatable due to remaining cross-track errors by considering the Ghobadi-Far et al. filtering, as it is shown numerically in the document. Moreover, the availability of these new type of LRI dataset is proposed and this would be really appreciated by research community. The quality of the presentation of this original work is very good and deserves to be published in ESSD once some minor corrections will be made (see my comments below).
MINOR CORRECTIONS
P.5. It would be simpler to explain that the raw along-track LRI observations are reduced in the GOCO6s software from known accelerations, including gravitational potential models listed in Table 1.
P.8. "using least-squares": is this a kind of 6-parameter least-square adjustment for each SH coefficient (constant term + linear trend + annual and semi-annual terms)? Please precise.
P.16. "20° of the equators": do you mean a 40° band of latitude centered on the Equator? Please precise.
P.20. "southeastern United States (SEUS)": "SouthEastern United States (SEUS)".
In all the document:
Please check the definition of acronyms, e.g. SEUS looks to be used in the text before being defined. Write "Line-O-Sight (LOS)" instaed of "line-of-sight (LOS)"
Text in the figures are sometimes too small, e.g. Figures 7 and 9. Please redraw them with larger text if necessary.
--- End of document ---

Citation: https://doi.org/10.5194/essd-2025-829-RC2
- AC3: 'Reply on RC2', Shin-Chan Han, 16 Jul 2026
  
  The comment was uploaded in the form of a supplement: https://essd.copernicus.org/preprints/essd-2025-829/essd-2025-829-AC3-supplement.pdf
  
  Citation: https://doi.org/10.5194/essd-2025-829-AC3

Miao Tang, Shin-Chan Han, Linguo Yuan, In-Young Yeo, Mehdi Khaki, Thomas Loudis Papanikolaou, Xinghai Yang, Yifu Liu, and Zhongshan Jiang

Data sets

GRACE Follow-On line-of-sight gravity data products M. Tang et al. https://doi.org/10.5281/zenodo.17766177

Miao Tang, Shin-Chan Han, Linguo Yuan, In-Young Yeo, Mehdi Khaki, Thomas Loudis Papanikolaou, Xinghai Yang, Yifu Liu, and Zhongshan Jiang

Viewed

Total article views: 929 (including HTML, PDF, and XML)

HTML	PDF	XML	Total	BibTeX	EndNote
483	407	39	929	48	87

HTML: 483
PDF: 407
XML: 39
Total: 929
BibTeX: 48
EndNote: 87

Views and downloads (calculated since 02 Feb 2026)

Month	HTML	PDF	XML	Total
Feb 2026	138	130	12	280
Mar 2026	95	103	13	211
Apr 2026	93	77	2	172
May 2026	48	60	2	110
Jun 2026	24	7	7	38
Jul 2026	85	30	3	118

Cumulative views and downloads (calculated since 02 Feb 2026)

Month	HTML	PDF	XML	Total
Feb 2026	138	130	12	280
Mar 2026	95	103	13	211
Apr 2026	93	77	2	172
May 2026	48	60	2	110
Jun 2026	24	7	7	38
Jul 2026	85	30	3	118

Viewed (geographical distribution)

Total article views: 883 (including HTML, PDF, and XML) Thereof 883 with geography defined and 0 with unknown origin.

Country	#	Views	%

Latest update: 26 Jul 2026

Short summary

This study presents a new global dataset that quantifies Earth’s mass changes by using gravity signals recorded from the GRACE spacecrafts. This dataset captures instantaneous mass changes and can reveal short-term dynamics that standard monthly data products do not provide. This enables prompt detection of rapid events such as flash droughts and floods and offers critical information to support improved monitoring of short-term water and mass variations.


Total:	0
HTML:	0
PDF:	0
XML:	0