Interação Radiação Solar - Atmosfera no Nordeste do Brasil: Análise Preliminar

Abstract

Actinography data (global and diffuse solar radiation) from five stations laid out at approximately 7oS, between the Atlantic coast and about 450 km inland of the Paraiba State, Brazil, have been analyzed. Only the data collected on clear (not cloudy) days have been considered. Under such atmospheric conditions, the data from all five stations exhibit similar behaviour. Global and direct daily irradiation (insolation) has essentially the same annual cycle, differing within 3-8%. Diffuse daily irradiation does not exceed 7% (winter) and 11% (summer) of the global irradiation. Global transmissivity measured for the wavelength interval of 0.4 - 2μis about 65%, and nearly constant during the year. Transmissivity for the directional fluxes ranges from 72 to 80%, for zenith angles up to about 45o.

Directional flux analysis permits a primary evaluation of atmospheric turbidity and maximum precipitable water. Inland, the latter would not exceed 0.9 g/cm2 during dry season (June-July), and approximately 4.0 g/cm2 during rainy season; Angstrom's turbidity factor should be less than 0.15. 

The results suggest that regional evaluation of precipitable water by the use of radiation measurements, could be improved if calibrated with local radiosonde data.