Effect of cloudiness on solar global, solar diffuse and terrestrial downward radiation at Badajoz (Southwestern Spain)

Abstract

Among all the components participating in the Earth radiation balance, clouds exhibit a large uncertainty in their characterization and quantification, partially due to their complex interaction with radiation. Although they play a key role attenuating and controlling the solar radiation and absorbing, scattering and emitting infrared radiation, their description is still very poor and more detailed studies are demanded. In order to contribute to that aim, simultaneous measurements of solar global irradiance, solar diffuse irradiance and downward infrared irradiance on a one-minute basis were performed at a radiometric station located in the Campus of the University of Extremadura in Badajoz (Spain). In this study the information provided by solar irradiance and its partitioning direct-to-diffuse, and by downward infrared irradiance is compared for some particularly interesting cases of study: cloud-free, partially cloudy and overcast. It is noted that infrared radiation does not exhibit the variability shown by the global solar radiation and directdiffuse partition in the different conditions analysed. The results emphasize the joint use of measurements of solar and infrared radiation which positively contribute to achieve a thorough description of the cloudiness field.