the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 13 Aug 2024
GravIS: mass anomaly products from satellite gravimetry
Abstract. Accurately quantifying global mass changes at the Earth’s surface is essential for understanding climate system dynamics and their evolution. Satellite gravimetry, as realized with the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) missions, is the only currently operative remote sensing system that can track large-scale mass variations, making it a unique monitoring opportunity for various geoscientific disciplines. To facilitate easy accessibility of GRACE/GRACE-FO results also beyond the geodetic community, the German Research Centre for Geosciences (GFZ) developed the Gravity Information Service (GravIS) portal (https://gravis.gfz-potsdam.de). This work aims to introduce the user-friendly mass anomaly products provided at GravIS that are specifically processed for hydrology, glaciology, and oceanography applications. These mass change data, available in both a gridded representation and as time series for predefined regions, are routinely updated as new monthly GRACE/GRACE-FO gravity field models become available. The associated GravIS web portal visualizes and describes the products, demonstrating their usefulness for various studies and applications in geosciences. Together with GFZ’s complementary information portal globalwaterstorage.info, GravIS supports widening the dissemination of knowledge about satellite gravimetry in science and society and highlights the significance and contributions of the GRACE/GRACE-FO missions for understanding changes in the climate system.
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Status: closed
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RC1: 'Comment on essd-2024-347', Anonymous Referee #1, 22 Sep 2024
The manuscript offers a thorough overview of the Gravity Information Service (GravIS), presenting mass anomaly products derived from GRACE and GRACE-FO data. The structure is well-organized, with detailed explanations of methodologies and products, and it provides substantial value by making complex satellite gravimetry data more accessible to non-experts in geodesy. This promotes broader use across various disciplines, including hydrology, oceanography, and glaciology. I would recommend publishing the manuscript in ESSD after addressing the following concerns.
Major Concerns:
(1) The GravIS tool is described as being designed for non-expert users, offering GRACE-related products without requiring them to process the data themselves. However, there are several existing tools that offer similar functionality. The authors should provide a comprehensive list of these available platforms and compare the key features of GravIS against them. This will help clarify the unique advantages of using GravIS over other tools on the market.
(2) To make the GravIS web portal more useful, several enhancements could be considered:
Data Sources: GravIS currently provides mass anomaly results based on GRACE solutions from GFZ and COST-G. It would be beneficial for users to have the option to compare these results with data from other prominent centers, such as CSR and JPL. Adding a cross-comparison feature with these additional datasets would greatly enhance the utility and versatility of the service.
Custom Region Selection: GravIS allows users to select predefined regions, such as river basins or climatically similar areas, for regional results. While river basin averages are commonly referenced in the literature, enabling users to define their own custom regions by drawing a polygon would add significant value. This would offer more flexibility for those focused on specific areas not covered by the existing predefined options.
Greenland and Antarctica Options: When dealing with the drainage basins in Greenland and Antarctica, only a single option is currently provided. Offering multiple options or further customization for these regions would make the tool more convenient for researchers working on these specific basins.
Ocean Bottom Pressure: I noticed that there doesn’t seem to be an option to provide results that consider self-gravitation and loading effects for ocean bottom pressure.
Batch Downloading: Implementing a batch download option would be extremely useful for researchers conducting global studies. The ability to download all time-series data at once would significantly streamline the process for users requiring extensive datasets for broader analyses.
Minor concerns:
(1)The manuscript alternates between "GRACE/GRACE-FO" and "GRACE/-FO." It would be clearer to choose one format and consistently use it throughout the manuscript.
In Section 2.1.3, it appears that the authors use results based on Swenson et al. (2008), while the uncertainties are derived from Sun et al. (2016). To my knowledge, Sun et al. (2016) improved upon Swenson et al. (2008) by incorporating self-attraction and loading effects. I am curious as to why the authors chose not to use the solutions by Sun et al. (2016) directly, given that these improvements could offer more accurate results.
(3)Ensure consistency of "GravIS" capitalization. It appears as "Gravis" in Line 471.
Citation: https://doi.org/10.5194/essd-2024-347-RC1 -
RC2: 'Comment on essd-2024-347', Anonymous Referee #2, 24 Sep 2024
This paper presents new GRACE/GRACE-FO mass anomaly products available on the Gravity Information Service (GravIS) portal, which includes various Level-2B and Level-3 datasets based on GFZ and COST-G. GravIS offers objectively processed and user-friendly Level-3 products (grids and regional averages) of mass anomalies for hydrology, glaciology, and oceanography applications. The authors also describe the processing steps applied to the GravIS mass anomaly products, the applications of GravIS products, and GravIS's update policies.
However, I have a few suggestions for improvement before the manuscript is published.
- Section 2.2 does not present the spatial uncertainty distribution for the Level-3 products. I believe it would be beneficial to include figures illustrating the spatial distribution of uncertainty for the three gridded products.
- Scientists without a geodetic background can also choose mascon products provided by CSR, GSFC, or JPL. Compared to mascon data, what are the advantages and distinguishing features of GravIS products in the context of hydrology, glaciology, and oceanography applications?
- Line 126-128, the subsequent section numbers are not increasing continuously. Is there any special consideration?
- In Section 2.2.3, unlike the ice-mass changes (Figs. 3 and 4) and TWS products (Fig. 5), there is no corresponding figure for the OBP product. I recommend including a diagram of the OBP gridded product along with a regional average time series.
- Line 226’Currently, the ICE-6G_D (VM5a) model (Peltier et al., 2018) is used to correct the GravIS Level-2B products for GIA’, and Line 228 ‘Note that GIA model errors are not propagated into the uncertainties of the Level-2B coefficients at present’. For users of Level-3 products, does this imply that the GIA model of gridded datasets can be adjusted simply by adding or subtracting the values from different GIA models?
- How is signal recovery performed during the inversion from L2 to L3, and how is signal leakage correction handled?
- Why is the resolution of the Gridded products set to 50 km?
- Comparison: It is necessary to compare the results of spherical harmonic coefficients with Mascon products, compare with the results from different institutions, existing studies, and other measurement methods, such as satellite altimetry results.
- Please provide all the codes, datasets, and results uploaded to an open-access link.
Citation: https://doi.org/10.5194/essd-2024-347-RC2 - AC1: 'Response to referee comments on essd-2024-347', Christoph Dahle, 30 Oct 2024
Status: closed
-
RC1: 'Comment on essd-2024-347', Anonymous Referee #1, 22 Sep 2024
The manuscript offers a thorough overview of the Gravity Information Service (GravIS), presenting mass anomaly products derived from GRACE and GRACE-FO data. The structure is well-organized, with detailed explanations of methodologies and products, and it provides substantial value by making complex satellite gravimetry data more accessible to non-experts in geodesy. This promotes broader use across various disciplines, including hydrology, oceanography, and glaciology. I would recommend publishing the manuscript in ESSD after addressing the following concerns.
Major Concerns:
(1) The GravIS tool is described as being designed for non-expert users, offering GRACE-related products without requiring them to process the data themselves. However, there are several existing tools that offer similar functionality. The authors should provide a comprehensive list of these available platforms and compare the key features of GravIS against them. This will help clarify the unique advantages of using GravIS over other tools on the market.
(2) To make the GravIS web portal more useful, several enhancements could be considered:
Data Sources: GravIS currently provides mass anomaly results based on GRACE solutions from GFZ and COST-G. It would be beneficial for users to have the option to compare these results with data from other prominent centers, such as CSR and JPL. Adding a cross-comparison feature with these additional datasets would greatly enhance the utility and versatility of the service.
Custom Region Selection: GravIS allows users to select predefined regions, such as river basins or climatically similar areas, for regional results. While river basin averages are commonly referenced in the literature, enabling users to define their own custom regions by drawing a polygon would add significant value. This would offer more flexibility for those focused on specific areas not covered by the existing predefined options.
Greenland and Antarctica Options: When dealing with the drainage basins in Greenland and Antarctica, only a single option is currently provided. Offering multiple options or further customization for these regions would make the tool more convenient for researchers working on these specific basins.
Ocean Bottom Pressure: I noticed that there doesn’t seem to be an option to provide results that consider self-gravitation and loading effects for ocean bottom pressure.
Batch Downloading: Implementing a batch download option would be extremely useful for researchers conducting global studies. The ability to download all time-series data at once would significantly streamline the process for users requiring extensive datasets for broader analyses.
Minor concerns:
(1)The manuscript alternates between "GRACE/GRACE-FO" and "GRACE/-FO." It would be clearer to choose one format and consistently use it throughout the manuscript.
In Section 2.1.3, it appears that the authors use results based on Swenson et al. (2008), while the uncertainties are derived from Sun et al. (2016). To my knowledge, Sun et al. (2016) improved upon Swenson et al. (2008) by incorporating self-attraction and loading effects. I am curious as to why the authors chose not to use the solutions by Sun et al. (2016) directly, given that these improvements could offer more accurate results.
(3)Ensure consistency of "GravIS" capitalization. It appears as "Gravis" in Line 471.
Citation: https://doi.org/10.5194/essd-2024-347-RC1 -
RC2: 'Comment on essd-2024-347', Anonymous Referee #2, 24 Sep 2024
This paper presents new GRACE/GRACE-FO mass anomaly products available on the Gravity Information Service (GravIS) portal, which includes various Level-2B and Level-3 datasets based on GFZ and COST-G. GravIS offers objectively processed and user-friendly Level-3 products (grids and regional averages) of mass anomalies for hydrology, glaciology, and oceanography applications. The authors also describe the processing steps applied to the GravIS mass anomaly products, the applications of GravIS products, and GravIS's update policies.
However, I have a few suggestions for improvement before the manuscript is published.
- Section 2.2 does not present the spatial uncertainty distribution for the Level-3 products. I believe it would be beneficial to include figures illustrating the spatial distribution of uncertainty for the three gridded products.
- Scientists without a geodetic background can also choose mascon products provided by CSR, GSFC, or JPL. Compared to mascon data, what are the advantages and distinguishing features of GravIS products in the context of hydrology, glaciology, and oceanography applications?
- Line 126-128, the subsequent section numbers are not increasing continuously. Is there any special consideration?
- In Section 2.2.3, unlike the ice-mass changes (Figs. 3 and 4) and TWS products (Fig. 5), there is no corresponding figure for the OBP product. I recommend including a diagram of the OBP gridded product along with a regional average time series.
- Line 226’Currently, the ICE-6G_D (VM5a) model (Peltier et al., 2018) is used to correct the GravIS Level-2B products for GIA’, and Line 228 ‘Note that GIA model errors are not propagated into the uncertainties of the Level-2B coefficients at present’. For users of Level-3 products, does this imply that the GIA model of gridded datasets can be adjusted simply by adding or subtracting the values from different GIA models?
- How is signal recovery performed during the inversion from L2 to L3, and how is signal leakage correction handled?
- Why is the resolution of the Gridded products set to 50 km?
- Comparison: It is necessary to compare the results of spherical harmonic coefficients with Mascon products, compare with the results from different institutions, existing studies, and other measurement methods, such as satellite altimetry results.
- Please provide all the codes, datasets, and results uploaded to an open-access link.
Citation: https://doi.org/10.5194/essd-2024-347-RC2 - AC1: 'Response to referee comments on essd-2024-347', Christoph Dahle, 30 Oct 2024
Data sets
Post-processed GRACE/GRACE-FO Geopotential GSM Coefficients GFZ RL06 (Level-2B Product) Christoph Dahle and Michael Murböck https://doi.org/10.5880/GFZ.GRAVIS_06_L2B
Post-processed GRACE/GRACE-FO Geopotential GSM Coefficients COST-G RL01 (Level-2B Product) Christoph Dahle and Michael Murböck https://doi.org/10.5880/COST-G.GRAVIS_01_L2B
GFZ GravIS RL06 Continental Water Storage Anomalies Eva Boergens et al. https://doi.org/10.5880/GFZ.GRAVIS_06_L3_TWS
COST-G GravIS RL01 Continental Water Storage Anomalies Eva Boergens et al. https://doi.org/10.5880/COST-G.GRAVIS_01_L3_TWS
GFZ GravIS RL06 Ocean Bottom Pressure Anomalies Henryk Dobslaw et al. https://doi.org/10.5880/GFZ.GRAVIS_06_L3_OBP
COST-G GravIS RL01 Ocean Bottom Pressure Anomalies Henryk Dobslaw et al. https://doi.org/10.5880/COST-G.GRAVIS_01_L3_OBP
GFZ GravIS RL06 Ice-Mass Change Products Ingo Sasgen et al. https://doi.org/10.5880/GFZ.GRAVIS_06_L3_ICE
COST-G GravIS RL01 Ice-Mass Change Products Ingo Sasgen et al. https://doi.org/10.5880/COST-G.GRAVIS_01_L3_ICE
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