Obtenção do saldo de radiação no Estado do Ceará utilizando imagens Modis.

Abstract

The energy balance components have been increasingly studied, especially because of their contribution to the management of water resources and numerical models and climate. The net radiation is one of these components and is used as an input to models that determine evapotranspiration. However, as it is a variable which is dependent on the nature of the surface, measuring weather stations enables exact values which cannot be used in heterogeneous areas. Thus, remote sensing is a useful tool because it allows weather and environmental information necessary to calculate the radiation balance in different geographical areas. Accordingly, this study aims to determine instantaneous and daily net radiation in the lower Jaguaribe water basin, through products of the MODIS sensor, onboard Aqua and Terra satellites. Thirty five images were used between the months of September at December, for the year 2005. The proposed methodology has been validated through instantaneous and daily net radiation calculated with data from a micrometeorological tower installed on an irrigated banana orchard located on the Frutacor Farm, in the municipality of Quixeré-CE, Brazil. The results were compared with data observed through the absolute and percent mean and root mean square errors. For the instantaneous net radiation, the mean error found was 7.40% for the Earth satellite and 15.61% for Aqua satellite. As for the mean daily balance errors were lower: 6.91% and 8.43% respectively. With these results, it is evident that the procedure is suitable for obtaining the radiation balance in the basin of the Lower Jaguaribe, especially with products from the Terra satellite.