Abstract. The amount of water stored on continents is an important constraint for
water mass and energy exchanges in the Earth system and exhibits large
inter-annual variability at both local and continental scales. From 2002 to
2017, the satellites of the Gravity Recovery and Climate Experiment
(GRACE) mission have observed changes in terrestrial water storage (TWS) with an
unprecedented level of accuracy. In this paper, we use a statistical model
trained with GRACE observations to reconstruct past climate-driven changes
in TWS from historical and near-real-time meteorological datasets at daily
and monthly scales. Unlike most hydrological models which represent water
reservoirs individually (e.g., snow, soil moisture) and usually provide
a single model run, the presented approach directly reconstructs total TWS
changes and includes hundreds of ensemble members which can be used to
quantify predictive uncertainty. We compare these data-driven TWS estimates
with other independent evaluation datasets such as the sea level budget,
large-scale water balance from atmospheric reanalysis, and in situ streamflow
measurements. We find that the presented approach performs overall as well
or better than a set of state-of-the-art global hydrological models (Water
Resources Reanalysis version 2). We provide reconstructed TWS anomalies at a
spatial resolution of 0.5∘, at both daily and monthly scales over
the period 1901 to present, based on two different GRACE products and three
different meteorological forcing datasets, resulting in six reconstructed TWS
datasets of 100 ensemble members each. Possible user groups and applications
include hydrological modeling and model benchmarking, sea level budget
studies, assessments of long-term changes in the frequency of droughts, the
analysis of climate signals in geodetic time series, and the interpretation
of the data gap between the GRACE and GRACE Follow-On missions. The
presented dataset is published at https://doi.org/10.6084/m9.figshare.7670849 (Humphrey and Gudmundsson, 2019) and updates will be
published regularly.