CRA-LICOM: A global high-frequency atmospheric and oceanic temporal gravity field product (2002–2024)

Abstract. Modeling sub-daily mass changes, dominated by the atmosphere and the oceans, is not only essential for understanding weather and climate change but also serves as a fundamental requirement for nearly all existing terrestrial or space-borne geodetic observations to perform signal separation. Removing these high-frequency mass changes, through the usage of so-called de-aliasing products, is of particular interest for satellite gravity missions such as GRACE and GRACE-FO to prevent the aliasing of short-term mass changes into seasonal and long-term mass variability. However, establishing a global observation network to monitor high-frequency gravity signals is impractical. Thus, ongoing efforts focus on simulating this high-frequency signal by driving atmospheric/oceanic numerical models with specific climate-forcing fields and assimilating observational data. Its realization relies on a complicated system and the uncertainty of obtained results is non-negligible for its dependency on selected forcing field and ocean model.

To explore the signal and uncertainty of de-aliasing products, we establish China’s first de-aliasing computation platform, independently. This is achieved by using the recently released CRA-40 (China’s first generation of atmospheric reanalysis) as forcing fields to drive our in-house 3-D atmospheric integration model and the LASG/IAP (State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics) Climate System Ocean Model 3.0 (LICOM3.0). With this new platform, we reproduce an alternative high-frequency atmospheric and oceanic gravity de-aliasing product, called CRA-LICOM, at 6 hourly and 50 km resolution, covering 2002–2024 at a global scale. The product is freely available at https://doi.org/10.11888/SolidEar.tpdc.302016. Inter-comparisons with the products of GFZ (Deutsches GeoForschungsZentrum) and validations against independent observations have revealed: (i) the current version of CRA-LICOM has well satisfied the requirement of the state-of-the-art satellite gravity missions, as well as other geodetic measurements, and (ii) despite agreement across most areas, considerable uncertainty is found at marginal seas near continental shelves, particularly at high-latitude regions. Therefore, scientific applications that aim to understand the fast-changing global water cycle, as well as mission design of future satellite gravity that seeks accurate gravity de-aliasing, can use our product as a reliable source. The current platform has the potential to be improved in terms of modeling and data assimilation capacity, which will be outlined in this study.