Sky-Cover Correlation within a Sky Dome

Abstract

A new utility for the use of whole-sky photographs has been developed through an effort to discern the structural pattern of correlations of cloud cover within an observer's sky dome. The photographs were taken from the National Weather Service observing site at Columbia, Missouri, and were originally assembled for the purpose of estimating probabilities of cloud-free lines of sight from the earth through the atmosphere. The procedure for determining the spatial correlation structure of sky cover within the sky dome starts with the defining and tabulating of a dichotomous sky-cover condition over small sectors of the sky dome, and then calculating the correlation associated with the tabulated sky conditions in each sector. This note shows that correlation of sky-cover conditions over a sky dome are very high, and that they are less degrading in the winter than in the summer. The results of this study can be applied to the estimation of cloud-free lines of sight to multiple satellites.