Terrestrial Total Water Storage Anomalies (TWSA) at 50 km resolution and below from assimilating GRACE/-FO mass change into models

Abstract:

TWSA has been suggested to be included in the framework of Essential Climate Variables (ECVs). However, satellite gravimetry observations from GRACE and GRACE-FO provide limited spatial resolution, and we still miss a future technology concept that would promise to resolve the 50 km scale – the grid width at which most global hydrological models operate.

Data assimilation can be viewed as integrating satellite gravimetry data with prior information from hydrological reasoning and climate forcing data. But at the same time, it provides an effective downscaling of the satellite-derived TWSA, which we hypothesize here is informed by modelling but not be overly dependent on a particular model or climate forcing data set.

Based on Eicker et al., 2014, we have extended our ensemble-based data assimilating framework to cover nearly half of the global land surface, to assimilate GRACE/-FO TWSA jointly with other remote sensing and in-situ observables, and to simultaneously estimate (calibrate) hydrological model parameters. In this presentation, we will compare downscaled GRACE/-FO results over Europe while assimilating into two different models. We will emphasize potential applications such as TWSA vertical disaggregation and drought identification from TWSA and satellite-derived ground- and surface water anomalies.