Clear and Cloud-Free Lines-of-Sight from Aircraft
Air Force surveys in geophysics
AIR FORCE GEOPHYSICS LAB HANSCOM AFB MA
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The AFGL in-flight line-of-sight program that was initiated to collect observations of the presence, or absence, of clouds and haze on lines- of-sight at various elevation angles form aircraft has been completed. Approximately 270,000 unique observations were collected. Observations were taken by flight crews of the U.S. Air Force, U.S. Navy, American Airlines, several other U.S. commercial carriers, and NATO countries. Data were obtained over most of the Northern Hemisphere. Observations taken within a 10 deg latitude-longitude sector were grouped together by altitude and season. The relative frequency of clear and cloud-free lines-of-sight are plotted in appropriate areas on Northern Hemisphere maps for various angular lines-of- sight. This paper describes the in-flight line-of-sight program, illustrates the presentation of data gathered, and gives a few examples of the utilization of this information.