A global analysis of water storage variations from remotely sensed soil moisture and daily satellite gravimetry

Information on water storage changes in the soil can be obtained on a global scale from different types of satellite observations. While active or passive microwave remote sensing is limited to investigating the upper few centimeters of the soil, satellite gravimetry can detect changes in the full column of terrestrial water storage (TWS) but cannot distinguish between storage variations occurring in different soil depths. Jointly analyzing both data types promises interesting insights into the underlying hydrological dynamics and may enable a better process understanding of water storage change in the subsurface.

In this study, we aim to investigate the global relationship of (1) several satellite soil moisture (SM) products and (2) non-standard daily TWS data from the GRACE and GRACE-FO satellite gravimetry missions on different time scales. The six SM products analyzed in this study can be categorized based on their degree of post-processing and the observed soil depth. Original level-3 surface SM data sets of SMAP and SMOS are compared to post-processed level-4 data products (surface and root zone SM) and a multi-satellite product provided by the ESA CCI.

We decompose the signal into seasonal to sub-monthly frequencies and carry out the comparison with respect to spatial patterns and temporal variability. An additional time-shift analysis will indicate differences in the temporal dynamics of soil moisture storage change in varying depth layers. We will apply tailored temporal masking of the time series to focus on time spans with favorable signal-to-noise ratio and to exclude time spans of snow cover or frozen soil. Additional data sets, such as precipitation events, will be added to the analysis to enhance the interpretation of the comparison of soil moisture and water storage variations.