This article presents a set of empirical models capable of extracting metrics quantifying the short-term variability of the solar resource based upon site/time specific satellite-derived hourly irradiance data. The model is derived from over 92,000 experimental hourly data points at twenty-four sites in the United States. The model returns four metrics characterizing intra-hourly variability, including the standard deviation of the global irradiance clear sky index, and the mean index change from one time interval to the next, as well as the maximum and standard deviation of the latter. The variability time scales addressed in this paper are 20 s, one-minute, 5 min and 15 min. The trends underlying the models are robust and show little site dependency. (C) 2011 Elsevier Ltd. All rights reserved.