After learning and understanding, we know that GRACE Level 2 RL06 data needs further post-processing before it can be used. Including the replacement of C20 items, C21, S21 items, different filtering methods, GIA correction and so on. Wondering if there is any program or code that can do this? And be able to manipulate the data freely.
Some tips on how to post-process GRACE Level 2 RL06 data are:
- Download the GRACE Level 2 RL06 data products from the GRACE Tellus website or the PO.DAAC website. You can choose between different data centers (JPL, CSR, GFZ) and different solutions (GSM, GAC, GAD). The GSM solution contains the spherical harmonic coefficients of the gravity field variations¹.
- Subtract a long-term mean field from the data products. You can use the mean field provided by GFZ or calculate your own mean field as an unweighted average of the available GSM products in a certain period².
- Replace the coefficients C20, C30, C21 and S21 and their formal standard deviations by values estimated from a combination of GRACE/GRACE-FO and Satellite Laser Ranging (SLR). You can use the values provided by GFZ or other sources².
- Apply a filter to reduce the noise and enhance the signal in the data products. You can use different types of filters, such as Gaussian, DDK, VDK, or Swenson¹. The choice of filter depends on your research question and the spatial and temporal resolution that you need.
- Subtract a linear trend caused by Glacial Isostatic Adjustment (GIA) from the data products. You can use a numerical model for GIA correction, such as ICE-6G_D_VM5a provided by GFZ or other sources².
- Insert geocenter coefficients (C10, C11, S11) into the data products. You can use the geocenter coefficients estimated by GFZ or other sources².
- Remove the estimated aliased signal of the S2 tide (161 days period) from the data products. This step is optional and depends on your research question².
(1) Data Updates & Announcements | Data – GRACE Tellus. https://grace.jpl.nasa.gov/data/data-updates/.
(2) Post-processed GRACE/GRACE-FO Geopotential GSM Coefficients GFZ RL06 .... https://dataservices.gfz-potsdam.de/gravis/showshort.php?id=escidoc:4175889.
(3) UTCSR/JPL GRACE Level-2 RL06 datasets release | PO.DAAC. https://podaac.jpl.nasa.gov/announcements/2018-07-16_UTCSR/JPL_GRACE_Level-2_RL06_datasets_release.
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