Obtenção do saldo de radiação através de imagens de satélite para a ilha do Bananal-TO.

Abstract

Remote sensing enables real time to identify changes that occur on Earth, resulting from various natural phenomena, but also due to anthropic processes. Many of these changes can be diagnosed from the determination and monitoring of radiative exchanges that take place at the surface. In this sense, this study aims to determine the net radiation at surface only by means of images generated by the Thematic Mapper (TM) of Landsat 5. at Ilha do Bananal - Tocantins State. Four TM - Landsat 5 images obtained on: June 03, July 21, August 06 and August 22, 2005 were used in the study. Thematic maps of albedo. Normalized Difference Vegetation Index - NDVI, land surface temperature - Ts (K), instantaneous net radiation - Rn,inst (WnT2) and daily net radiation - Rn24 (W m"2), were generated using the SEBAL algorithm. The Rn values were validated with measurements made in a micrometeorological tower installed inside the Ilha do Bananal. For two images (July 3 and August 22, 2005) two different areas (disturbed and natural vegetation) were selected to better assess the environmental impacts resulting from human occupation of that area. It can be seen large changes in deforested sites compared to sites with native vegetation: in deforested areas the albedo and land surface temperature increased and the same time NDVI and Rn (instantaneous and daily) were smaller than those observed in the native areas. The results show the influence and importance of native vegetation for the local climate. According with validation of the results the daily net radiation at surface presented EMR, EMA and REQM errors respectively equals to 1.95%, 2.78 W m"2 and 3.36 W m"2. According to the results obtained in this work we conclude that the methodology used for Rn determination presented good accuracy.