A multi-scales surface energy balance system for operational actual surface evapotranspiration monitoring

The evaporative fraction is an indicator of high interest for irrigation management and the monitoring of crop water needs. The DEMETER project provided opportunities to evaluate its possible use in an Irrigation Advisory Service (IAS) in an operational context, using high resolution satellite images. Mapping this indicator with pixels of a few tens of meters of size on an area of regional extent leads to associate different processes and parameters of different characteristic scales together. The Multi-Scale Surface Energy Balance System methodology proposed here focuses on the adequacy of the data used with the theoretical framework incorporated in models, both in terms of canopy to region scale integration of surface fluxes and in terms of time scale of surface and atmospheric processes. Moreover, the implementation was adapted in regard to operability constraints related to IAS, i.e. processing time and data availability. An experiment made with MSSEBS over one of the DEMETER reference area is presented, using a set of images acquired in the field of the SPARC 2003 campaign, during an entire growing season.