Input management
batch import Level-2 GSM products, preserve product-center, release, month, lmax, and replacement metadata.
Satellite Gravity Field
GRACE Level-2 Processing Workflow
From GSM spherical harmonics to gridded EWH products
Technical notes and reproducible workflow records for transforming GRACE and GRACE-FO Level-2 spherical harmonic solutions into physically consistent equivalent water height products.
00
Learning Center
Start from a topic, then move between workflow notes, method records, data products, and software releases.
WorkflowProcessing chain
Acquire, preprocess, filter, synthesize, and validate Level-2 products.
MethodsFiltering notesCompare Gaussian, decorrelation, DDK, HSAF, and leakage correction routes.
DataProducts and referencesTrack GSM coefficients, EWH grids, Mascon references, masks, and diagnostics.
ArticlesReproducible recordsRead project notes with assumptions, checks, and processing contracts.
01
Software capability overview
content copy for the GRACE Level-2 desktop workflow software. The section can later be replaced with real screenshots, versioned feature descriptions, and release-specific notes.
Filter comparison
run Gaussian, decorrelation, DDK, and HSAF routes side by side with explicit product tags and diagnostics.
Product preview
inspect global maps, basin averages, anomaly time series, and residual stripe patterns before export.
Basin analysis
compute area-weighted TWSA, annual/semi-annual amplitudes, linear trends, leakage-corrected series, and comparison tables.
Reproducible export
write outputs with configuration snapshots, figure previews, processing logs, and checksum-ready release folders.
Quality control
collect map checks, spectral checks, unit checks, reference-product comparison, and missing-month audit results.
a screenshot of the desktop processing workspace, including dataset selection, filter routing, and export status.
a figure or short animation showing gridded EWH preview, color scale control, and product comparison.
time-series plots, annual amplitude maps, trend summaries, and leakage-correction reports.
02
Processing Pipeline
Click any processing node to inspect the scientific contract behind the step.
01 Acquire Collect monthly Level-2 GSM Stokes coefficients and product metadata.
Principle
Input should be treated as a Level-2 gravity-field solution, usually monthly GSM spherical harmonic coefficients. The product name, processing center, release, maximum degree/order, time stamp, missing month flag, and reference frame must remain explicit.
Formula
\[S(\theta,\lambda,t)=\{\Delta C_{lm}(t),\Delta S_{lm}(t)\},\quad 0\le m\le l\le l_{\max}\]
Configuration example
- product
- HUST-Grace2024 / CSR RL06 / GFZ RL06 / JPL RL06
- max_degree
- 60
- monthly_solution
- true
Quality checks
- Verify the product release and lmax.
- Preserve the month identifier before any interpolation.
- Keep the raw input immutable.
02 Preprocess Apply low-degree replacement, GIA correction, background-field alignment, and anomaly baseline removal.
Principle
Preprocessing converts monthly coefficients into a consistent anomaly field. Typical operations include degree-1 geocenter replacement, C20/C30 replacement using SLR, GIA correction, optional destriping preconditions, and subtraction of a stated mean field.
Formula
\[\Delta C'_{lm}=\Delta C_{lm}-\Delta C_{lm,\mathrm{mean}}-\Delta C_{lm,\mathrm{GIA}}\]
Configuration example
- replace_degree1
- true
- replace_c20_c30
- SLR
- gia_model
- ICE-6G_D
- baseline
- 2004-01..2009-12
Quality checks
- State the baseline period.
- Record all replacement products.
- Never mix corrected and uncorrected products under one tag.
03 Filter Route de-striping, spatial smoothing, DDK, and HSAF products through explicit product tags.
Principle
Filtering reduces correlated north-south striping and random high-degree noise while preserving physically interpretable mass signals. Gaussian, Fan, PnMm decorrelation, DDK, and HSAF should be routed as separate products rather than overwritten arrays.
Formula
\[\hat{x}=F\{x\},\quad F\in\{\mathrm{Gaussian}(r),\mathrm{Fan}(r),\mathrm{PnMm},\mathrm{DDK}_k,\mathrm{HSAF}\}\]
Configuration example
- GAUSS_300
- Gaussian smoothing, 300 km radius
- FAN_300_P3M6
- Fan filter with P3M6 decorrelation
- DDK4
- anisotropic regularization product
- HSAF
- Hankel spectrum analysis filtering
Quality checks
- Save every filter result with a unique tag.
- Record all radii and polynomial parameters.
- Compare signal loss, residual stripes, and leakage behavior.
04 Synthesize Transform corrected spherical harmonics into gridded equivalent water height anomalies.
Principle
Spherical harmonic synthesis converts corrected coefficients into equivalent water height. The Love-number correction, Earth radius, water density, grid resolution, land/ocean mask, and units must be consistent across products.
Formula
\[\mathrm{EWH}(\theta,\lambda)=\frac{a\rho_e}{3\rho_w}\sum_{l=0}^{l_{\max}}\sum_{m=0}^{l}\frac{2l+1}{1+k_l}\bar{P}_{lm}(\cos\theta)\left(\Delta C_{lm}\cos m\lambda+\Delta S_{lm}\sin m\lambda\right)\]
Configuration example
- output_unit
- cmEWH
- grid
- 1deg or 0.5deg
- love_numbers
- Wahr / Farrell
- lmax
- 60
Quality checks
- Confirm cmEWH/mmEWH units.
- Use one grid convention for comparisons.
- Keep masks and coastline buffers versioned.
05 Validate Check maps, basin averages, leakage correction, trends, and independent product consistency.
Principle
Validation should combine visual quality control with quantitative diagnostics. Basin-mean time series, annual amplitude, trend, leakage-corrected regional products, Mascon comparison, hydrology models, and altimetry are separate evidence layers.
Formula
\[\mathrm{TWSA}_{\mathrm{basin}}(t)=\frac{\sum_i A_i\,\mathrm{EWH}_i(t)}{\sum_i A_i}\]
Configuration example
- diagnostics
- map_preview, basin_mean, annual_amp, trend, rmse
- references
- CSR_Mascon, GLDAS, Hydroweb
Quality checks
- Review maps before statistics.
- Report leakage/scaling assumptions.
- Compare against at least one independent product when possible.
03
Data Products
Keep data products explicit, versioned, and auditable.
Gridded EWH
Monthly equivalent-water-height anomalies on controlled grids with product metadata and diagnostics.
Read preview note
Mascon comparison
Independent products for checking spatial patterns, basin averages, and long-term behavior.
Read workflow note04
Method Notes
A compact record of each filter family and its routing contract.
Gaussian / Fan / DDK
Baseline filter families for reproducible comparison and controlled product tags.
Read article05
Recent Articles
Latest notes from the processing log.
A reproducible GRACE Level-2 workflow Filter products as a graph, not a checklist Preview is a quality-control surface
All articles Software releases
Access versioned installers, release notes, and software usage information from the download page.
Good processing is transparent, testable, and reproducible.
Workflow first, results follow.