USE OF NOAA AVHRR DATA COMBINED WITH AN AGROMETEOROLOGICAL MODEL FOR EVAPORATION MAPPING

A new agrometeorological model was derived from the EARTH model (elaborated at the French Meteorological Office by Choisnel). It uses classical meteorological network daily data, and combines water and energy exchanges between soil and atmosphere at one hour intervals through an energy budget. The surface temperature is computed every hour as the solution of the energy budget equation. The model is first briefly presented. A comparison was made between our model and NOAA AVHRR satellite derived surface temperature; it shows good consistency. Simulated data from actual meteorological information were then used to generate simplified relationships for estimating daily evaporation: ET(d) - RN(d) = A - B(T(s) - T(a)), where RN(d) is the daily net radiation, T(s) is the surface temperature at 14.00 UT, T(a) is the maximum air temperature. The sensitivity of the coefficients A and B to the roughness length is also studied. Finally, an example of mapping of evaporation is given, using our algorithm combined with meteorological network data and information on land-use, for south-west France, in the framework of the HAPEX-MOBILHY experiment.