ESTIMATING MEAN CLOUD AND CLIMATOLOGICAL PROBABILITY OF CLOUD-FREE LINE-OF-SIGHT
AIR FORCE ENVIRONMENTAL TECHNICAL APPLICATIONS CENTER SCOTT AFB IL
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A method is described which provides an estimate of the probability of cloud-free line-of-sight between any two levels at any angle to the horizon for locations having standard surface-observed cloud data. The method uses the mean cloud amount between the surface and each higher kilometer level to estimate the mean cloud amount at any level, the mean cloud amount above any level and the mean cloud amount between any two levels. Analyses of sunshine and total cloud cover by time of day provide a basis for estimating probability of cloud-free line-of-sight through the whole atmosphere as a function of mean total cloud cover and viewing angle. This relationship is used to estimate the probability of cloud-free line-of-sight at any angle between any two levels for which the mean cloudiness between the levels is known or estimated. Height vs distance profiles of estimated probability of cloud-free line-of-sight can be prepared manually or by computer for any kilometer height reference levels.