Persistence, Runs, and Recurrence of Visibility

A total of 511,056 hourly observations of visibility, taken over a 13-year period at nine stations, was studied to obtain a better understanding of the characteristics of persistence, runs, and recurrence. Each hourly visibility observation was categorized as either greater than or equal to 10 miles, greater than or equal to 5 miles, less than or equal to 3 miles, less than or equal to 1 mile (in summer), or less than or equal to 0.25 mile (in winter). 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 the probability that any visibility category 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).