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Hydrological model

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GloFAS v4

.0 hydrological model

renalysis and forecasts are generated using LISFLOOD OS, a physically based spatially distributed hydrological model. More detailed information about this hydrological model (e.g. modelled physical processes) are available here.

Specifically, GloFAS v4 makes use of LISFLOOD OS v4.1.3.  Compared to the LISFLOOD OS version used to produce GloFAS v3, LISFLOOD OS v4.1.3 features updates in the hydrological routines, such as pixel-by-pixel computation of water infiltration into the soil, and improvements in the modelling of water abstraction for anthropogenic use. Moreover, LISFLOOD v4.1.3 benefits of significant improvements in the management of large input datasets and in the computational performances.

Consistently with all the previous GloFAS versions, the computations for GloFAS v4 are completed with daily time steps for all the hydrological processes, while sub-daily (4 hours) time steps are used for the modelling of river routing. All the output variables are available with daily resolution.

Implementation 

Static maps

Accurate representation of the rainfall-runoff processes in different climatic and socio-economic contexts requires a set of maps showing the morphological, pedological, vegetation, land cover, land and water use characteristics of the catchments. About 80 implementation maps are required as input to LISFLOOD OS. This set of implementation maps is referred to as “static maps” or “surface fields dataset”.

The spatial resolution of the GloFAS v4

implementation maps is 0.05 degrees, further information on the preparation, features, and availability of the dataset can be found here: CEMS-Flood surface field dataset - Copernicus Emergency Management Service - CEMS - ECMWF Confluence Wiki.

Meteorological forcings

The meteorological variables used by GloFAS v4 (and GloFAS v3) are total precipitation, 2-metre temperature, 2-metre dew temperature, 10-metre U wind component, 10-metre V wind component, surface solar radiation downwards, surface thermal radiation. These variables are provided as input to GloFAS from different meteorological datasets, depending on the purpose of the model simulation: hydrological reanalysis, medium range forecast, seasonal forecast. The list of meteorological datasets used for each purpose is available here.from GloFAS meteorological forcings - Copernicus Emergency Management Service - CEMS - ECMWF Confluence Wiki. The meteorological variables are upsampled from their native resolution to 0.05 degrees resolution using bilinear interpolation: the interpolation algorithm is implemented in the open-source pre-processor pyg2p. It is here noted that nearest neighbor interpolation was used for 0.1 degrees GloFAS set up (v3 and preceding versions).

2-metre temperature, 2-metre dew temperature, 10-metre U wind component, 10-metre V wind component, surface solar radiation downwards, surface thermal radiation are used to compute  reference values of evapotranspiration according to the Penmann-Monteith equation, which is implemented in the open source pre-processor LISVAP.

LISFLOOD OS then takes as input total precipitation, 2-metre temperature, and reference evapotranspiration. Similarly to all the previous GloFAS versions, the computations for GloFAS v4 are completed with daily time steps for all the hydrological processes, and sub-daily (4 hours) time steps for the river routing. All the output variables are available with daily time steps.

References

[1] Choulga, Moschini, Mazzetti, Grimaldi, Disperati, Beck, Salamon, and Prudhomme. “ Technical note: Surface fields for global environmental modelling”. Submitted for publication to HESS, MS type: Technical notefrom each source are pre-processed as described in this page.