Estimating Mean Cloud and Climatological Probability of Cloud-Free Line-of-Sight

Climatological Probability of Aircraft Icing

“…Cloud data for the 59000-, 10,000-, 15.000-, and 20,000-foot altitudes were computed by the method developed in AWSTR 186 (3]. Mean seasonal cloud amount data for 306 stations were utilized in this study.…”

Haze-Free and Cloud-Free Lines-of-Sight Through the Atmosphere

“…In earlier articles by McCabe (1965) and Lund (1965), it is also pointed out that clear does not always mean cloud-free. McCabe (1965) states:…”

“…Long records of sunshine and sky cover observations were used by Lund (1965Lund ( , 1966 and McCabe (1965) to estimate probabilities of clear lines-oi-sight through the atmosphere. Lund (1966) devoted most of the introduction of his 7 article to explaining how a "clear" line-of-sight was defined for his study.…”

“…With the exception of a part of the work of McCabe (1965), which was based upon a set of aircraft cloud layer reports, the preceding studies pertain to seeing through the entire atmosphere. Only the collection by aircraft crews of in-flight line-of-sight observations along specific angles will provide data for estimating probabilities of clear, cloudy, or hazy lines-of-sight between flight levels and the surface, and flight levels and space.…”

“…1 tenths. The dashed curve shown in Figure 7 was obtained by entering McCabe's (1965) graph with mean total cloud cover of 61 percent. As expected, the probabilities obtained were much higher than those obtained from the whole-sky photographs.…”