LAUSR

In order to reduce high frequency non-tidal mass changes, while inverting for the Earth’s time-variable gravity fields from the Gravity Recovery And Climate Experiment (GRACE) measurements, it is usual to apply the Atmospheric and Oceanic De-aliasing (AOD1B) products. However, limitations in these products count as a potential threat to the accuracy of time-variable gravity fields derived from GRACE, as well as its follow-on mission(s). Therefore, in this study, we show to what extent the GRACE-type gravity recovery procedure is sensitive to different non-tidal atmospheric background models. For this, we evaluate the atmospheric parts of the GeoForschungsZentrum (GFZ)’s AOD1B RL05 and RL06, as well as those computed as a part of the European Space Agency Earth System Model ESA-ESM, and the ITG3D model. These data products employ different atmosphere fields (operational and reanalysis data or their combination) from the European Centre for Medium-Range Weather Forecasts (ECMWF) as inputs, and they are also computed by implementing different 2-dimensional or 3-dimensional (2-D or 3-D) integration methods. The accuracy of these products is assessed by comparing the resulting GRACE K-Band Range-Rate (KBRR) residuals computed for time-variable gravity field inversions using each of them separately as a background model. Our investigations during 2006 indicate that: (i) applying ESA-ESM and ITG3D decreases averaged KBRR residuals by 2.8 nm/s and 3.4 nm/s compared to those reduced by the official RL05 products. (ii) Projecting these residuals onto the spatial domain indicates that the improvement covers 78.4% and 78.9% of the globe, respectively. (iii) We find that, compared to ESA-ESM, ITG3D can further reduce the KBRR residuals by 1.8 nm/s at regions of high latitudes, which likely improve the uncertainty of ice mass estimations. Our investigation of the AOD1B RL06 products covers 2006-2010, which indicates the advantage of using the higher temporal sampling, i.e. 3-hourly reanalysis data. Applying the RL06 reduces the averaged KBRR residuals by 44.2 nm/s with respect to the use of the RL05 for gravity field inversion. We, therefore, conclude that the integration method of ITG3D and utilizing reanalysis data with higher (than 6-hourly) temporal sampling rate are beneficial for GRACE-like gravity inversion such as the GRACE Follow-On mission with laser interferometric ranging system.