Models to estimate incident solar radiation on Seropédica, Rio de Janeiro

Abstract

Incident solar radiation (R_s) is usually used as an input variable in growth simulation models and yield of agricultural crops, in the design of alternative energy systems, buildings desing, weather, irrigation projects and food preservation, among others. However, in Brazil, there are few studies that evaluated the performance of different models in estimating R_s. Therefore, the aim of the study is to evaluate the Hargreaves-Samani, Thornton-Running and Weiss models to estimate R_s in the municipality of Seropédica, Rio de Janeiro. We used hourly measurements of solar radiation (R_s, KJ m^-2) and maximum (t_x,°C) and minimum (t_n,°C) air temperature obtained from Ecologia Agrícola station (EA), between January/2008 to December/2013. Normality (Shapiro-Wilks and Jarque-Bera) and homogeneity of variance (Bartlett) tests were applied to the data set. The performance of the models was evaluated based on different statistical parameters (r² RMSE, d, Ï_s and Student's t-test). The results indicated the rejection of the variance normality hypothesis of the standardized residuals by Shapiro-Wilks and Jarque-Bera tests. Bartlett's test indicated the presence of heterogeneity of model estimates. Hargreaves-Samani and Thornton-Running models obtained high values forr² and low values for d. Hargreaves-Samani (coastal) model excelled in relation to other, being more suitable for estimating the R_s in the municipality of Seropédica, Rio de Janeiro.