CEMS-Flood meteorological forcing are derived from observations or from NWPs: the list and usage of data sources is provided by CEMS-Flood meterological forcing and land surface data - Copernicus Emergency Management Service - CEMS - ECMWF Confluence Wiki.

This page briefly explains the pre-processing of the observations or NWPs to prepare the gridded dataset required as input to the hydrological model.

• In-situ observations for EFAS are collected, quality checked, and interpolated by the CEMS-Meteorological Data Collection Centre. The quality checks are presented in, the interpolation algorithm is Spheremap. PAPER BY VERA

• 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.