Balanço de radiação em áreas irrigadas utilizando imagens Landsat 5-TM.

Abstract

The main objective of the present study was the determination of the balance radiation at surface, based on seven spectral bands o f Landsat 5 - Thematic Mapper. Two images, taken on December 04, 2000 and October 04,2001, involving irrigated areas o f Nilo Coelho Project, part o f the Sobradinho Lake, native vegetation areas and part of the urban areas o f Petrolina, PE and Juazeiro, BA, were considered. It was applied the Surface Energy Balance Algorithm for Land - SEBAL, proposed by Bastiaanssen (1995), in order to calculate the albedo and the land surface temperature for each pixel o f the images. The incoming short wave radiation and the incoming long wave radiation were assessed by data from a weather station. In general, the radiation balance of the scene as a whole was larger in 2000, when it reached an aerial average value of 615.0 W.m"2 . In 2001, the averaged Rn value reached 583.9 W."2, although in some selected areas within the studied scene, Rn in 2001 was larger than the one of2000. It might be caused by occurrence of some rainfall events in the area studied on December of 2000. That would have affected the albedo and the land surface temperature mainly in the non-irrigated areas. The results obtained in irrigated orchards, when compared with other studies, show that the approach is confidant and have great importance.