Cloud-Free Line-of-Sight Calculations.

by R. Robert Rapp, C. Schutz

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A method for computing the probability of having a cloud-free line-of-sight (CFLOS) to or from a given point on the earth, using three-hourly synoptic weather reports of clouds. The method is based on whole-sky photographs taken during daylight hours over a period of three years at Columbia, Missouri. The computational procedure is an effort to eliminate an apparent oversimplification in previously published data that results from the use of mean cloud cover, an unrelated vertical cloud distribution, and sunshine data. Present results are at variance with those earlier estimates, but compatible with recent observations actually taken from aircraft. Although the CFLOS estimates obtained are, by nature, uncertain, the range of uncertainty was estimated by using published empirical data and a quantitative error analysis. 30 pp. Bibliog.

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