A time domain triangle method approach to estimate actual evapotranspiration: Application in a Mediterranean region using MODIS and MSG-SEVIRI products

In this study, spatially distributed estimates of regional actual evapotranspiration (ET) were obtained using a revised procedure of the so called "triangle method" to parameterize the Priestley-Taylor φ coefficient. In the procedure herein proposed, named Time-Domain Triangle Method (TDTM), the triangular feature space was parameterized considering pairs of Ts-VI values obtained by exploring, for each pixel, only their temporal dynamics. This new method was developed using time series products provided by MODIS and MSG-SEVIRI sensors. Moreover the proposed procedure does not depend on ancillary data, and it is only based on remotely sensed vegetation indices and day-night time land surface temperature differences.Two different test areas located in Sicily were selected for testing and validating the approach. Satellite ET rates were validated versus directly measured fluxes of mass (ET) obtained by eddy covariance (EC) towers during the observation period 2010-2012.The proposed approach predicts daily ET rates with an acceptable level of accuracy for practical purposes; therefore, the TDTM can be considered as a simple and effective tool to easily estimate, at regional scale, spatial and temporal changes of this key-variable related to water resource management, agriculture, ecology and climate change.