Assessing the stability of AOD1B atmosphere–ocean non-tidal background modelling for climate applications of satellite gravity data: long-term trends and 3-hourly tendencies

Abstract

SUMMARYThe GRACE Atmosphere and Ocean Level-1B (AOD1B) product is routinely applied in the processing of satellite gravimetry data to mitigate the impact of temporal aliasing. Spurious trends, low-frequency signals or bias jumps in the background model data can, if unaccounted for, introduce biases into the global gravity solutions which might be interpreted erroneously in subsequent geophysical analyses. Here, we examine the most recent release, RL07, of AOD1B for such artefacts. A focus is placed on the transition from the atmospheric re-analysis ERA5 to operational weather model data, in January 2018, which coincides with the gap between the missions GRACE and GRACE-FO. We find that linear trends computed from 1975 to 2020 are well below 30 Pa a–1 for all components of RL07. The assessment of 3-hourly tendencies gives no indication of bias jumps and shows that the transition in atmospheric data does not have an adverse effect on the consistency of RL07. We conclude with a comparison of the variability of both AOD1B RL06 and RL07 in the context of their application in satellite gravimetry.