Monthly averaged global and diffuse solar radiation in the Pacific Northwest

Monthly averaged correlations between diffuse and global insolation are presented for five locations in Oregon and Idaho. Data collected over a three year period was utilized to obtain the correlations. The statistical accuracy of the correlations was improved through the use of moving averages. Linear regression fits appear to be adequate for our data. The correlations obtained appeared not to be influenced by either altitude or climatic conditions. However, a repeating semi-annual pattern due to turbidity effects seems to be present.