On the relation between insolation and climatological variables—II. Prediction of insolation at Fort Hood, Texas

Abstract

Total insolation data were taken at hourly intervals at Fort Hood in Central Texas from September, 1974 to the present. This paper presents a digest of the data through the end of August, 1975. By analyzing the hourly variation of insolation on clear days, a simple correlation was devised for predicting the total insolation at any hour of any clear day in the year. The standard deviation for predicting daily total insolation on clear days is 10.2 Langleys compared to the average daily total of 300–700 Langleys. On unclear days, the fraction of clear weather insolation received at ground level was correlated with cloud cover and visibility. For any combination of cloud cover and visibility, the insolation can thereby be predicted. This correlation is found to be least accurate at low insolation, where solar energy systems are non-functional. At higher insolation, the accuracy improves, but is never as accurate as for clear days. With this correlation, monthly total insolation is predicted to within 5–10%. For the year September, 1974–August, 1975, the correlation predicted total insolation 1% lower than the observed value.