Spatial and Temporal Variations in Long-Term Normal Percent Possible Solar Radiation Levels in the United States

Abstract

The purpose of this study was to analyze the time and space variations in long-term monthly-averaged daily percent possible solar radiation levels in the United States. Both principal components analysis and harmonic analysis were used to identify the influences of various synoptic-scale climatological phenomena on solar radiation receipt. Generally, an annual cycle was found with maximum percent possible radiation levels occurring in July. In many regions the temporal variance structure deviated from this general annual cycle. The results, which are useful in both theoretical and practical studies, lead to a better understanding of the climatology of solar radiation in the United States.