| Section C | C index | 681-689 of 1157 terms |
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column—A columnar ice crystal with hexagonal cross section and having aspect ratio (diameter to length) as much as 10 to 1. The column may be either solid or hollow with ends plane, pyramidal, truncated, or hollow. Pyramids and combinations of columns are included in this class. It is one of the common ice crystals found in cirrus clouds.
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columnar resistance—In atmospheric electricity, the electrical resistance of a column of air 1 m square, extending from the earth's surface to some specified altitude. Measurements extending to an altitude of 18 km indicate that the atmospheric columnar resistance to that height amounts to about 1017 ohm m−2. Probably, this is only slightly less than the total columnar resistance from earth to ionosphere. In fact, roughly half of the total columnar resistance from the earth to 18 km is contributed by the lowest 3 km of the column where, in addition to the greater density of the air, the high concentration of atmospheric particulates leads to a relatively high population of poorly conducting large ions rather than the more mobile small ions. Total columnar resistance does not vary greatly with either time or locality. By contrast, the columnar resistance of the lowest fraction of a kilometer varies greatly, causing fluctuations in the atmospheric electric field at sea level, especially in industrial areas of highly variable atmospheric pollution. See ion mobility.
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comb nephoscope—(Obsolete.) A direct-vision nephoscope constructed by L. Besson in 1897. It consists of a comb comprising equispaced vertical rods attached to a cross piece. The comb is affixed to one end of a column 2.5–3 m (8–10 ft) long and is supported on a mounting that is free to rotate about its vertical axis. In use, the comb is turned so that the cloud appears to move parallel to the tips of the vertical rods.
Middleton, W. E. K., 1969: Invention of the Meteorological Instruments, Johns Hopkins Press, Baltimore, p. 271.
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COMBAR code—(Short for combat aircraft code.) A synoptic code used by combat aircraft to report observable meteorological elements in groups of five-digit numbers.
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comber—A large wave that rolls over or breaks on a beach, reef, etc.
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combination coefficient—A measure of the specific rate of disappearance of small ions due to either 1) union with neutral Aitken nuclei to form new large ions; or 2) union with large ions of opposite sign to form neutral Aitken nuclei. Dimensionally, a combination coefficient is identical with the physically similar recombination coefficient. Both types of combination coefficients exhibit mean values of the order of 10−5cm3s−1 at sea level, while the recombination coefficients are typically about one order of magnitude smaller. See recombination, small-ion combination.
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combustion nucleus—A condensation nucleus formed as a result of industrial, transport, or natural combustion processes. The chemical nature of such nuclei may vary almost as much as can the nature of reactants in combustion processes, but because of the prevalence of sulfur impurities in many fuels, the process transforming sulfur dioxide (SO2) to sulfur trioxide (SO3) and thence sulfuric acid is perhaps the most important in producing combustion nuclei. Sulfuric acid is very hygroscopic and hence can serve to nucleate atmospheric condensation processes. The role of the ammonium ion (NH4+), which is formed in some combustion processes, is probably of almost equal importance to that of the sulfite (SO3−2) and sulfate (SO4−3) ions. Such nuclei may be completely or (in association with soot) partly soluble in water.
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comfort chart—As used by the American Society of Heating and Air Conditioning Engineers, a diagram showing curves of relative humidity and effective temperature superimposed upon rectangular coordinates of wet-bulb temperature and dry-bulb temperature. Upon this chart (one for each chosen rate of air movement) may be indicated comfort zones bounded by relative humidity and effective temperature curves; these zones may be determined for various conditions (different seasons, different nations, different races, different clothing, etc.).
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