A revised Makkink formula is presented to estimate the Reference Crop Evapotranspiration (ET0), as defined by the FAO, requiring incoming solar radiation and air temperature only and allowing operational ET0 mapping with geostationary satellite (MSG) imagery. For 2008 daily MSG-ET0 compare well with 'ground-truth' data collected over well-watered 'FAO-grass'. The project is carried out in the context of the LSF SAF project (http://landsaf.meteo.pt/). It is argued that solar radiation must be preferred over measured net radiation as input variable for ET0 calculations.

4 Pags., 2 Figs. A derived version of this contribution was published later as Chapter Book: De Bruin H.A.R., Trigo I.F., Gavilán P., Martínez-Cob A., González-Dugo M.P. 2012. Reference crop evapotranspiration estimated from geostationary satellite imagery. En: Remote Sensing and Hydrology. Proceedings of a Symposium held at Jackson Hole, Wyoming, EE.UU., September 2010. IAHS Publ. 352: 111-114.

Peer reviewed