Estimativa do saldo de radiação para distintas condições de céu usando dados de sensoriamento remoto para o Nordeste Brasileiro.

Abstract

The radiation balance on the Earth's surface is a variable of primary interest in areas such as hydrology, in climate studies and in agriculture. In certain situations, the presence of clouds is detected that prevent the obtaining of surface data information through satellite images. In this sense, the research aims to generate the balance of radiation in different sky conditions, used to the methodology of Bisht and Bras (BB10) to estimate the components of instantaneous Rn and Rn, 24h through, exclusively, products of the MODIS sensor. The impact of the cloud on the radiation components that reach the surface was deduced according to the data provided by the product MOD06, in addition, the following products were used: MOD07, MOD11 and MCD43A3. From these, cloud data, atmospheric profile data, surface albedo and emissivity are extracted. The algorithm was applied throughout the Brazilian Northeast, and to measure the accuracy of the estimates, validation was performed, whose experiments are on three different soil coverings (degraded, recovered and preserved) in the Caatinga area during the years of 2014, 2015 and 2016. Among the estimated components, short-wave radiation is the most influenced by clouds and, consequently, the most affected in the radiation balance. The validation of the results, in general, proved to be coherent, thus confirming that the methodology applied in this study was satisfactory. The algorithm, according to its execution, was able to obtain good estimates of the components, the instantaneous radiation balance and the daily balance, even under cloudy sky conditions, using only MODIS sensor products. Thus, it was found that the BB10 methodology and the method improved by Araújo (2010), for estimating the Rn, 24h, were satisfactory, and the validation of the model showed that the REMQ error obtained for the Rn, 24h was of 31.34, 22.41 and 19.96 W m- 2, for degraded, recovered and preserved area, respectively, which are in agreement with those found in the literature.