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Proceedings Paper

Assessing daily actual evapotranspiration through energy balance: an experiment to evaluate the selfpreservation hypothesis with acquisition time
Author(s): A. Maltese; F. Capodici; G. Ciraolo; G. La Loggia; G. Rallo
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Paper Abstract

An operational use of the actual evapotranspiration estimates requires the integration from instantaneous to daily values. This can commonly be achieved under the hypothesis of daytime self-preservation of the evaporative fraction. In this study, it has been evaluated the effect of this assumption on the assessment of daily evapotranspiration from proximity sensing images acquired at hourly intervals over a homogeneous olive groove. Results have been validated by comparison with observations made by a micrometeorological (EC-flux tower) and an eco-physiological (sap flux) sensor. SEBAL model has been applied to thermal and multispectral images acquired during a clear day on August 2009 trough a FLIR A320G thermal camera and a Tetracam MCA II multispectral camera, installed on a tethered helium balloon. Thermal and multispectral images were characterized by very high spatial resolution. This experiment aims to analyze two effects: 1) the consistency of the self-preservation hypothesis for daily estimates of the actual evapotranspiration from hourly assessments at different times of the day; 2) the effects of the spatial resolution on the performances of the energy balance model. To evaluate the effects of the spatial resolution, semi-hourly observations made by a flux tower and sap-flow measures were compared to the evapotranspiration estimates performed using downscaled images at resolutions close to canopy sizes (2, 5 and 10 m). Results show that the best estimates are obtained with a spatial resolution comparable to the average size of the canopy with images taken approximately at 10 UTC.

Paper Details

Date Published: 16 October 2013
PDF: 13 pages
Proc. SPIE 8887, Remote Sensing for Agriculture, Ecosystems, and Hydrology XV, 888718 (16 October 2013); doi: 10.1117/12.2029873
Show Author Affiliations
A. Maltese, Univ. degli Studi di Palermo (Italy)
F. Capodici, Univ. degli Studi di Palermo (Italy)
G. Ciraolo, Univ. degli Studi di Palermo (Italy)
G. La Loggia, Univ. degli Studi di Palermo (Italy)
G. Rallo, Univ. degli Studi di Palermo (Italy)

Published in SPIE Proceedings Vol. 8887:
Remote Sensing for Agriculture, Ecosystems, and Hydrology XV
Christopher M. U. Neale; Antonino Maltese, Editor(s)

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