An experiment was installed in the Campos dos Goytacazes County, RJ, in a sugar cane crop area where solar incident irradiation (Rs↓), outgoing radiation reflected by the surface (Rs↑) and net radiation(Rn) were measured. Data from four periods were analyzed: one in the tillering stage (109 DAS), two in the development of sprouts (197 e 258 DAS) and one during maturation (294 DAS). The daily variation of each radiation balance element and the relation between net and global radiation were evaluated and parameters such as albedo, long wave exchange coefficient and heat coefficient were estimated. The albedo showed increasing values as the crop leaf area index (LAI) increases with mean value of 0.24 during tillering stage, 0.24 during the development of sprouts and 0.27 to 0.30 during maturation. The mean albedo for all stages was 0.28 ± 0.03. The linear regression between net radiation and net short wave radiation showed a determination coefficient of 0.99. Heat coefficient (β) varied from 0.061 to -0.133 and the long wave exchange coefficient (λ) from -0.057 to 0.154. These coefficients turn out to be useful tools in surface and atmosphere energy transformation because they showed significant differences during the phenological stages of sugar cane crop.
solar irradiance; albedo; thermal coefficient; sugar cane
