ausblenden:
Schlagwörter:
-
Zusammenfassung:
This study has been run in the context of the European Union research project G3P (Global Gravitybased
Groundwater Product) on developing Groundwater storage (GW) as a new product for the
EU Copernicus Services. GW variations can be derived on a global scale by subtracting from total
water storage (TWS) variations based on the GRACE/GRACE-FO satellite missions variations in
other water storage compartments such as soil moisture, snow, surface water bodies, and
glaciers. Due to the nature of data acquisition by GRACE and GRACE-FO, the data need filtering in
order to reduce North-South-oriented striping errors. However, this also leads to a spatially
smoothed TWS signal. For a consistent subtraction of all individual storage compartments from
GRACE-based TWS, the individual data sets for all other hydrological compartments need to be
filtered in a similar way as GRACE-based TWS.
In order to test different filter methods, we used compartmental water storage data of the global
hydrological model WGHM. The decorrelation filter known as DDK filter that is routinely used for
GRACE and GRACE-FO data introduced striping artifacts in the smoothed model data. Thus, we can
conclude that the DDK filter is not suitable for filtering water storage data sets that do not exhibit
GRACE-like correlated error patterns. Alternatively, an isotropic Gaussian filter might be used. The
best filter width of the Gaussian filter is determined by minimizing the differences between the
empirical spatial correlation functions of each water storage and the spatial correlation function of
GRACE-based TWS. We also analyzed time variations of correlation lengths such as seasonal
effects. Finally, the selected filter widths are applied to each compartmental storage data set to
remove them from TWS and to obtain the GW variations.
