Estimativa da radiação de onda longa em diferentes regiões do Brasil.

Abstract

The long—wave radiation emitted by the atmosphere (Rol,atm) is of vital importance for many applications that require radiation balance and energy balance. Weather stations typically do not include Rol,atm sensors, and, therefore, measurements of the Rol,atm usually are not available for a particular location and period of interest. However, there are empirical models that estimate the Rol,atm using variables commonly measured in weather stations, as air temperature, relative humidity and partial vapor pressure. The objective of this work is to evaluate five different empirical models, Aubinet 1 (Al), Aubinet 2 (A2), Aubinet 3 (A3), Aubinet 4 (A4) and Gabathule et al. (G) cloudiness in five regions of Brazil, using two data banks, SONDA and ARM, at daily level, and time for a station located in Brasília during the daytime and night time periods. In order to analyze the reliability of the Rol,atm values, atm estimated, statistical methods were applied, in order to evaluate the approximate estimated data. The Pearson correlation coefficient (r), mean absolute error (EMA), root mean square error (REQM), mean relative error (ERM), Willmott concordance index and confidence index performance of Camargo and Sentelhas. For daily level the best model for the Midwest region was G, since in terms of EMA, REQM and ERM, obtained the lowest values for three of the four sky conditions. The same G model also performed well in the North and Northeast regions, even if it only has data in two sky conditions. For the Southeastern region of the country the best A2 model with three of the four sky conditions and for the South region of the country the best model was A4, having two of four conditions being this model as the best answer. For hourly level in the station located in the Center West in the daytime period the best model was also G. At night hours a simple linear correlation was used between the relative humidity divided by 100, and the emissivity the obtained equation was used to generate an emissivity for the Rol,atm estimated at night, reaching a r d of 0.92 for a condition of clean sky, the highest value r among all sky conditions also taking into account the r values obtained in the daytime period, in this station located in the Center West specifically.