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 LISFLOOD OS. Specifically, the required inputs are total precipitation, 2-metre temperature, and reference evapotranspiration. 

• Observations for EFAS are collected, quality checked, and interpolated by the CEMS-Meteorological Data Collection Centre (more details in this page). The interpolation algorithm is Spheremap: more details can be found in Thiemig et al. 2022

• NWPs are upsampled from their native resolution to the desired resolution of EFAS and GloFAS using the interpolation algorithms implemented in the open-source pre-processor pyg2p. Nearest neighbor interpolation was used up to EFAS v4 and GloFAS v3 (5km European and 0.1 degrees global set-ups, respectively). Bilinear interpolation is used for EFAS v5 and GloFAS v4 (1 arcmin European and 0.05 degrees global set-ups, respectively).

Reference values of evapotranspiration are computed using either observations or NWPs and following the Penmann-Monteith method, which is implemented in the open source pre-processor LISVAP.