MATLAB functions to estimate the GRACE terrestrial water storage anomaly based on the improved point-mass solution

MATLAB functions to estimate the Terrestrial Water Storage Anomaly (TWSA) based on the Improved Point-Mass (IPM) solution, which further details are available in Ferreira et al. (2020).

The codes are provided only for educational purposes and can be modified as necessary by potential users.

The main goal is to solve the inverse problem of estimating TWSA based on the gravitational potential at GRACE's altitude (~500 km). The potential can be computed from the unfiltered spherical harmonic coefficients (Level-2 data). It is also necessary to provide the a priori information, which consists of a grid containing TWSA. This can be computed from the filtered spherical harmonic coefficients using the standard methods (Wahr et al., 1998).

An example considering the residual gravitational potential at 500 km altitude (observations) and the a priori information, TWSA, are available at a resolution of 3-by-3 degrees, which is suitable for most of the hardware available. Finer resolution is possible at the cost of computations resources.

References:

Ferreira, V.G., Yong, B., Seitz, K., Heck, B., Grombein, T., 2020. Introducing an Improved GRACE Global Point-Mass Solution—A Case Study in Antarctica. Remote Sens. 12, 3197. https://doi.org/10.3390/rs12193197

Wahr, J., Molenaar, M., Bryan, F., 1998. Time variability of the Earth’s gravity field: Hydrological and oceanic effects and their possible detection using GRACE. J. Geophys. Res. 103, 30,205-30,229. https://doi.org/10.1029/98JB02844