Catchment-Averaged Monthly Water Budget Net Flux Timeseries 2002--2011 from ICON v2.6.4 Simulations, GRACE TWS, and GRDC Discharge over the EURO-CORDEX Domain

Description: This data set provides monthly resolved timeseries of area-averaged continental water net fluxes across the terrestrial-atmospheric boundary, assessed over a selection of 22 major river catchments in the EURO-CORDEX domain, covering the period 2002-06/2011-05. The term 'net flux', here, refers to the surplus of water mass gained from precipitation (P) to the ground, after consideration of water mass losses through non-precipitative water fluxes towards the atmosphere (E, effectively: evaporation). In simplified terms: it describes how much more water from precipitation each month stays at the ground compared to how much is evaporated back into the atmosphere. In addition to (P,E), this data set also provides the corresponding components' term in the continental water budget equation, i.e. $\frac{dS}{dt}+R$, as in $\frac{dS}{dt}=P-E-R$, where $\frac{dS}{dt}$ is the temporal change in terrestrial water storage S, and R is river discharge (streamflow). Data sources: P-E net flux is computed from individual P- and E-timeseries, assessed over the catchment area upstream from the river gauge stations, respectively. The timeseries are derived from ICON v2.6.4 simulations (da Silva Lopes et al., 2025) who employed three different sea surface temperature (SST) products as lower boundary condition over the ocean. For reference, we also include corresponding fluxes derived from ECMWF ERA5 Reanalysis. The different sources are used in fully consistent manner, i.e. none of the provided series here has 'mixed' P,E-sources. dS/dt is derived by means of monthly central differences from COST-G (GRACE satellite gravimetry). See netCDF header for details. R is catchment-averaged equivalent water height of observed river discharge as provided by GRDC, Koblenz, Germany. The individual GRDC ID numbers in the netCDF file names (and in the meta data therein) correspond to the hydroshed shapes available from GRDC. Each catchment shape defines the integration kernel for the aggregation of monthly water fluxes, respectively. Water budget residual: If all components of the budget equation were perfectly determined, their residual would approach zero. However, in reality this is hardly ever the case and systematic offsets can hint to, e.g., model insufficiencies or observation biases. Hence, in addition to both budget terms "P-E" and "dS/dt+R", this data set also provides readily computed timeseries of the water budget residual (i.e. the mis-closure) $\epsilon=P-E-R-dS/dt$. One will find that in many cases the PE variant with colder skin-type SST leads to ~10--15 mm/year less precipitation over the assessed regions. For easier visual comparison of such offsets, the residual timeseries are additionally provided in a 18-months post-filtered version (variables with "*_18M" within each netCDF). A more detailed description of the method can be found in the corresponding publication. Please note that the provided data set does NOT contain timeseries of individual components as not all its sources may be freely re-distributed. This data set is intended for use in regional climate analysis, model validation, and impact studies, including hydrological and ocean-land-atmosphere interaction research. Users are advised to consider the characteristics and limitations of regional climate model simulations when interpreting the data. Given the limited model time span, it is not advisable to interpret climate-related trends from the time-series, but instead focus on validation, model dynamics and impact-pathways. Data format: The data are stored in netCDF4 format with timestamps given in seconds since 2002-06-01T00:00:00. There is one .nc file per catchment, but Zenodo optionally provides the download of all files combined in a zip archive. File names follow the format DETECT_SST_PE-Budget_{GRDC_ID}_{STATION}_{RIVER}_v{VERSION}.nc, where: GRDC_ID: Seven-digit integer GRDC identification number of the river gauge station; corresponding HydroSHEDS-based shapes of watershed boundaries are provided by GRDC. STATION: GRDC name of the river gauge station, with blanks or special characters replaced where appropriate. RIVER: Name of the stream (river); note that this can also be a tributary to a major stream, e.g. Tisa, which is a sub-region of the Danube Ceatal-Izmail catchment. VERSION: three number code to represent the file version, e.g. "v1_0_0" represents the initial upload. NetCDF variables and naming scheme: Name (dimension) Type Units Description GRDC_ID int32 GRDC identifier of river gauge stationname string GRDC name of the catchment's defining station rivername string GRDC name of the catchment's river area uint64 m**2 Nominal surface area of the river catchment time int64 seconds since 2002-06-01T00:00:00 Mid-of-month time; this variable is the dimension for all flux variables PE_{era5sst_dly, era5skt_hly, mursst_dly, ERA5rea} (time) float mm month**-1 Boundary net flux (P-E) of the three SST set-ups and ERA5 reference dSdtR (time) float mm month**-1 Combined flux of terrestrial water storage change and river discharge Residual_{era5sst_dly, era5skt_hly, mursst_dly, ERA5rea} (time) float mm month**-1 Terrestrial water budget residual (P-E-R-dS/dt) Residual_{era5sst_dly, era5skt_hly, mursst_dly, ERA5rea}_18M (time) float mm month**-1 Terrestrial water budget residual with 18-month Gaussian smoother (post)