Reference Evapotranspiration (METREF)

NRT Product available since Aug 2016


Product Documentation

This operational product is documented in the Algorithm Theoretical Basis Document (ATBD), Product User Manual document (PUM) and the Product Output Format document (POF) The validation results for this product are available in the (VR) document.


Data Policy

The use of LSA SAF products in publications is kindly requested to be duly acknowledged:
METREF was provided by the Satellite Application Facility on Land Surface Analysis (LSA SAF; Trigo et al., 2011)

Trigo, I. F., C. C. DaCamara, P. Viterbo, J.-L. Roujean, F. Olesen, C. Barroso, F. Camacho-de Coca, D. Carrer, S. C. Freitas, J. García-Haro, B. Geiger, F. Gellens-Meulenberghs, N. Ghilain, J. Meliá, L. Pessanha, N. Siljamo, and A. Arboleda, 2011: The Satellite Application Facility on Land Surface Analysis. Int. J. Remote Sens., 32, 2725-2744, doi: 10.1080/01431161003743199



Reference evapotranspiration, ETo, is the evapotranspiration rate from a clearly defined reference surface. The concept was introduced to allow the estimation of the evaporative demand of the atmosphere independently of crop type, crop development or management practices. ETo corresponds to the evapotranspiration from a hypothetical extensive well-watered field covered with 12 cm height green grass having an albedo of 0.23 would experience under the given down-welling short-wave radiation.


Product Description

The LSA SAF METREF provides daily ETo [mm/day] estimated from daily global radiation derived from SEVIRI/MSG, as this is the main driver of evapotranspiration over the extensive reference surface. The algorithm is described in the LSA SAF documents (see ATBD) and in DeBruin et al (2016).
The characteristics of land surfaces impact the radiation budget and influence the atmosphere boundary layer. The LSA METREF product, however, does not use atmospheric humidity and only presents a slight dependency on near surface air temperature. LSA SAF METREF is not affected by local effects, such as surface aridity or local advection.


Algorithm Description



Data Characteristics

The METREF product is computed within the area covered by the MSG disk. For each time-slot, the ETo field and respective Quality Control (QC) data are disseminated in HDF5 format; the relevant information concerning the data fields is included in the HDF5 tributes.


Product Uncertainties




De Bruin, H. A. R., I. F. Trigo, F. C. Bosveld and J.F. Meirink: A thermodynamically based model for actual evapotranspiration of an extensive grass field close to FAO reference, suitable for remote sensing application, J. Hydrometeor., doi: 10.1175/JHM-D-15-0006.1, 2016.

Example of Product