Quantifiers for the solar irradiance variability: A new perspective

This paper focuses on variability in solar irradiance time series. Six quantifiers for the solar irradiance variability, very different in their nature, are analyzed. One of them, based on the cumulative distribution function of the increments of clearness index time series, is developed in this study. The new quantifier is obtained by integrating the complementary cumulative distribution function over all values of the increments. The same level of variability is expressed by different quantifiers of different magnitudes. In order to surpass this obstacle a normalizing procedure is applied. This is a key task in comparing the output of different quantifiers toward a unique standard in the evaluation of the solar irradiance variability. As application, a new multi-parameter ranking procedure for classifying the days according to the solar irradiance variability is introduced.