Determinação do albedo de superfície em áreas irrigadas do projeto Jaíba (Minas Gerais), a partir de imagens Landsat

Abstract

The present study aimed to determine the surface albedo in irrigated areas of the Jaíba Project, located in the north of Minas Gerais state, between the coordinates UTM of 595204/626309 and 8308401/8341257 N - Zone 23. In the preparation of this project, it was used satellite images from Landsat 5 –TM, path/row 219/70, with images from January 31, Julian Day 31 (JD 31), April 21 (JD 111), June 24 (JD 175), July 10 (JD 191) and September 12 (JD 255) of the year 2011. The determination of surface albedo was performed according to the procedures of the algorithm SEBAL (Surface Energy Balance Algorithm for Land) based on the radiance of reflective channels of the TM sensor. The values of surface albedo of days 31 and 111 (San Francisco River) were in order of 9 to13%, associated with the increased of sediment load caused by the rainy season. The results of the albedo in natural vegetation places showed greater variation, in order of 9 to 16%. This result may be associated to the hole of seasonality over native vegetation and pasture, where the day 255 has presented the larger variation in the analyzed period, corresponding to the dry season. The values observed in the irrigated areas were in order of 16 to 23%, while the values in degraded vegetation, pasture and bare soil varied in order of 23 to 32%, consistent with the scientific literature.