Remote sensing may be used to identify changes that occur in land use of Earth, resulting from natural and/or anthropic processes. Many of these changes can be diagnosed from the monitoring of radiative exchanges that take place at the surface. In this sense, this study aims to determine the net radiation at surface, by means of sateLλi te images covering Bananal Island, in the State of Tocantins, Brazil. TM-Landsat 5 images obtained in 2005 (cloud free), were used to generate maps of instantaneous and daily net radiation (Rn) based on SEBAL. The Rn values were validated with measurements performed in a micrometeorological tower installed within the Bananal Island. The instantaneous Rn values varied between 488.0 and 535.0 W m-2; while the daily Rn values varied between 132.7 and 145.3 W m-2. The disturbed areas showed decrease in net radiation. The daily net radiation presented relative mean error, mean absolute error and square root of mean square error equal to 1.95%, 2.78 W m-2 and 3.36 W m-2; respectively. According to the results, it may be concluded that the methodology used for Rn determination presented good accuracy.
Landsat 5; albedo; land surface temperature; radiation budget
