Assessment of Land Surface and Atmospheric Model Mass Flux Using Water Balance Techniques and GRACE/GRACE-FO Data

GRACE mission data is used to derive variations in terrestrial water storage in order to evaluate approaches to the water balance. The data in the span of the GRACE and GRACE Follow-On missions is analyzed, and long-term behavior of a variety of basins is characterized. Terrestrial water storage variations are calculated via a combination of flux quantities from land surface models and atmospheric reanalyses using two common water balance approaches as well as a third approach using a novel algorithm for basin boundary discretization. Results are used to evaluate the new approach and form an understanding of its limitations, in relation to both the model data ingested as well as the characteristics of the regions in question.  From the results, we observe significant variations in model performance over diverse geography and climatic conditions, such as diminished accuracy in atmospheric reanalyses under the effect of long term drought. These observations suggest utility as a diagnostic to assess and inform improvement in the studied models.