Abstract
This study inter-compares the most important retrieval methods that derive atmospheric turbidity from measured Direct Normal Irradiance. A number of parametric solar radiation models are used backward to estimate the atmospheric turbidity indices. To reduce error propagation, each turbidity index are derived using a specific set of models. Then, an inter-comparison between all the selected models are carried out to establish degree of agreement between the models. High-resolution solar radiation data, at one-minute intervals, taken from Plataforma Solar del Desierto de Atacama, is used in this investigation.
Results shows that seven models (among 11 models) generally agree well, with a maximum difference of 0.004 in the estimation of the Angstrom coefficient. Besides, Kasten's pyrheliometric method performs as good as sophisticated solar radiation models such as MET STAT, MWLT 1, MWLT2, REST and Yang.