Monitoring evapotranspiration at landscape scale in Mexico: applying the energy balance model using remotely-sensed data

Thermal and spectral remotely sensed data make the monitoring from flux energy variables in the land atmosphere interface possible. Therefore, remotely sensed data can be used as an alternative to estimate actual evapotranspiration (ET) by applying the energy balance equation. In order to test the applicability of this approach in Mexico, MODIS (Moderate Resolution Imaging Spectroradiometer) estimations from land surface variables are used at 16-day intervals of composite data. Ancillary information is collected from 2000 ground stations. The methodology includes the Simplified Surface Energy Balance model (SSEB) and its intercomparison with a combined model from the Surface Energy Balance Algorithm (SEBAL) and the Two Source Energy Balance (TSEB) procedures. Preliminary results applied to one 16-day interval during winter, 2002, showed that ET is spatially structured at a landscape level. The most significant discrepancies between estimations are found due to the general assumptions applied to each model. Secondly, the use of interpolated ancilliary data from local observations, along with remote sensing data, provides a better representation of spatial variations of ET with SEBAL-TSEB model for the study period. There is not enough evidence to asses objectively the performance of both applied procedures. Further testing is required to evaluate at a local scale the reliability from estimations.