DELGADO, Jéssica Rodrigues.
Résumé:
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.
