Persistence, Runs, and Recurrence of Sky Cover

A total of 511, 056 hourly observations of total sky cover, taken over a thirteen-year period at nine stations, was studied to obtain a better understanding of the characteristics of persistence, runs, and recurrence. Each hourly total sky cover observation was categorized as either zero-tenths (clear), less than or equal to three-tenths, greater than or equal to eight-tenths, or ten-tenths (overcast). Probabilities of each category were estimated from relative frequencies determined from this large data sample and were compared with some theoretical models. The models can be applied to estimate probabilities that any of the above sky cover categories will be observed for sequences of x hours, or more; for exactly x hours; or at time t and also at time t+x hours. (Author).