Abstract
ON Sunday, January 24, at about 09.15, the sky was nearly covered with a sheet of alto-cumulus; this had a straight edge, there being quite clear sky low down in the east. In the northern and western parts of the sky and up to the zenith there were numerous streaks of cirrus uncinus, that is, cirrus streaks with the ends upturned; these were without a doubt below the alto-cumulus. All the clouds were moving from about north-west; the apparent motion of the cirrus was faster than that of the alto-cumulus. The upturned ends of the cirrus were to the southward, the streaks trailing away to the northward. The cirrus appeared dark against the clouds above it. The height of the alto-cumulus was measured with a range-finder. Three separate observations were made on different patches of cloud, at angular altitudes of 30°, 22°, and 20°; the heights obtained were 10,500 ft., 10,140 ft., and 10,260 ft. These are in very fair accordance, and there is, therefore, not much doubt that the height of the alto-cumulus sheet was between 10,000 and 10,500 feet; the cirrus must, therefore, have been lower, but how much lower it is impossible to say. The best development of the cirrus was at the time I have named, but some cirrus was seen below the alto-cumulus until about mid-day.
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CAVE, C. Cirrus at a Lower Level than Alto-cumulus. Nature 117, 199 (1926). https://doi.org/10.1038/117199c0
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DOI: https://doi.org/10.1038/117199c0
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