ALBERT

Description: Limited by the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) measurement principle and sensors, the spatial resolution of mass flux solutions is about 2–3° in mid-latitudes at monthly intervals. To retrieve a mass flux solution in the Tibetan Plateau (TP) with better visual spatial resolution, we combined truncated singular value decomposition (TSVD) and Tikhonov regularization to solve for a mascon modeling. The monthly mass flux parameters resolved at 1° are smoothed to about 2° by truncating the eigen-spectrum of the normal equation (i.e., using the TSVD approach), and then Tikhonov regularization is applied to the truncated normal equation. As a result, the terms beyond the native resolution of GRACE/GRACE-FO data are truncated, and the errors in higher degree and order components are dampened by Tikhonov regularization. In terms of root mean squared errors, the improvements are 27.2% and 12.7% for the combined method over TSVD and Tikhonov regularization, respectively. We confirm a decreasing secular trend with −5.6 ± 4.2 Gt/year for the entire TP and provide maps with 1° resolution from April 2002 to April 2019, generated with the combined TSVD and Tikhonov regularization method.

Description: Dividing the sea-level budget into contributions from ice sheets and glaciers, the water cycle, steric expansion, and crustal movement is challenging, especially on regional scales. Here, Gravity Recovery And Climate Experiment (GRACE) gravity observations and sea-level anomalies from altimetry are used in a joint inversion, ensuring a consistent decomposition of the global and regional sea-level rise budget. Over the years 2002-2014, we find a global mean steric trend of 1.38 ± 0.16 mm/y, compared with a total trend of 2.74 ± 0.58 mm/y. This is significantly larger than steric trends derived from in situ temperature/salinity profiles and models which range from 0.66 ± 0.2 to 0.94 ± 0.1 mm/y. Mass contributions from ice sheets and glaciers (1.37 ± 0.09 mm/y, accelerating with 0.03 ± 0.02 mm/y**2) are offset by a negative hydrological component (-0.29 ± 0.26 mm/y). The combined mass rate (1.08 ± 0.3 mm/y) is smaller than previous GRACE estimates (up to 2 mm/y), but it is consistent with the sum of individual contributions (ice sheets, glaciers, and hydrology) found in literature. The altimetric sea-level budget is closed by coestimating a remaining component of 0.22 ± 0.26 mm/y. Well above average sea-level rise is found regionally near the Philippines (14.7 ± 4.39 mm/y) and Indonesia (8.3 ± 4.7 mm/y) which is dominated by steric components (11.2 ± 3.58 mm/y and 6.4 ± 3.18 mm/y, respectively). In contrast, in the central and Eastern part of the Pacific, negative steric trends (down to -2.8 ± 1.53 mm/y) are detected. Significant regional components are found, up to 5.3 ± 2.6 mm/y in the northwest Atlantic, which are likely due to ocean bottom pressure variations.

Description: RECOG - REgional COrrections for GRACE: The dataset contains a monthly global earthquake correction for GRACE-level 3 total water storage anomalies (TWSA) for CSR, GFZ and ITSG solutions. The correction is monthly available from January 2003 to December 2016 and is used to correct for the Sumatra-Andaman (2004) and Tohoku (2011) earthquake by using a method described in Einarsson et al. (2010), where a co- and a post-seismic signal is modeled. The files contain longitude, latitude, time and the correction field of TWSA on an 0.5° grid. In the processing of the data, we included replacing lower degree coefficients, DDK3 filtering, reduced a temporal mean from 2003 to2016 and applied a correction for glacial isostatic adjustment. More information about the computation and application of the earthquake correction can be found in Deggim et al. (2020, in preparation). For more information about the GRACE processing visit following website: https://www.apmg.uni-bonn.de/daten-und-modelle/grace_level3_monthly_solutions, last access 12.08.2020.

Description: The global land water storage (GLWS) data set is produced by assimilating (Eicker at al., 2014) gridded GRACE and GRACE-FO-derived total water storage anomalies (TWSA) into the WaterGAP global hydrological model using the Parallel Data Assimilation Framework (PDAF, Nerger and Hiller, 2013). The resulting data set represents thus an optimal synthesis of GRACE data and all data sets that went into the hydrological model. This synthesis seeks to fit GRACE (-FO) TWSA grids within error bars, and at the same time it solves the horizontal and vertical water balances as represented in the hydrological model, again within error bars. To this end, the uncertainty of the hydrological model simulation is represented via an n-member ensemble, where we take into account the uncertainty of forcing (precipitation and radiation) data as well as the uncertainty of some model calibration parameters. As a result, when no GRACE (-FO) data is available, the GLWS data set represents the mean – or the median additionally provided - of an ensemble where each member is dynamically consistent with the model. It is important to understand that this mean/median depends on the ensemble creation and thus will differ from published WaterGAP standard runs, even if there is no GRACE data within a particular month. It is also important to understand the assimilation-derived GLWS data set does not represent a simple downscaling of the GRACE data, i.e. spatial smoothing of GLWS does not necessarily correspond to GRACE (-FO) TWSA. The monthly level 3 GLWS data represent the total water storage anomaly (TWSA) on 0.5° grids and level 2 GLWS data represent groundwater, soil moisture and surface water. They are provided now for 01/2003 to 12/2019. Additionally, the standard deviation is provided (computed from the ensemble). As default, GLWS is derived from the ensemble mean, here, we additionally provide the ensemble median. The main updates with respect to the release 001 were the use of an updated version of WaterGAP as well as minor bug fixes in the assimilation.

Description: TND-IGG RL01: This dataset is the first release of thermospheric neutral densities (TND) processed at the Institute of Geodesy and Geoinformation (IGG), University of Bonn, Germany. TNDs are derived from accelerometer measurements of the satellites GRACE-A, CHAMP and Swarm-C. For GRACE-A and CHAMP we first calibrate the accelerometer data within a precise orbit determination procedure (Vielberg et al., 2018). For Swarm-C we use the calibrated along-track accelerations from ESA (Siemes et al., 2016). In a second step, solar and Earth radiation pressure accelerations according to Vielberg and Kusche (2020) are reduced from the calibrated accelerometer data. The resulting atmospheric drag is then related to the thermospheric neutral density following the direct procedure by Doornbos et al. (2010) with temperature and density of atmospheric constituents from the empirical model NRLMSIS2.0. We apply an accommodation coefficient of 0.93 for GRACE, 0.82 for Swarm and 0.85 for CHAMP. Detailed information about the processing can be found in the ReadMe.txt and in Vielberg et al. (2021, in review). The final thermospheric neutral densities with a temporal resolution of 10 seconds are provided as monthly netCDF files.