| Section C | C index | 271-279 of 1157 terms |
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China Coastal Current—A surface current in the East China Sea and Yellow Sea flowing southward along the Chinese coast from Bohai Gulf to Taiwan. It is driven by the northeast monsoon in winter and continues against the southwest monsoon through the summer, strengthened by river runoff from monsoonal rainfall. Taking in most of the waters from the Yangtze River, it contributes greatly to the increased summer transport of the Tsushima Current.
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chinook arch—A mountain-wave cloud form that occurs along the east slopes of the Rocky Mountains, particularly in the Montana–Alberta area, where the range runs roughly north–south. The arch cloud has a sharp western (upwind) edge and a great cross-wind extent in the lee of and parallel to the Rockies. Arch clouds can stretch a few hundred km or more north–south as measured from the ground and from satellite. The arch refers to the shape of the western edge of the wave cloud as seen by an observer looking westward from the ground on the plains east (to the lee) of the mountains. The arch is especially noticeable when the blue sky to the west of it is completely clear of other cloud layers. Glider pilots sometimes refer to the clear area as the “window.” The distinctive shape of the arch is due to the cloud height (usually middle or high cloud), its large cross-wind extent along the horizon, and the perspective of the observer, who sees the cloud and the mountain range converge with distance to the north and south. The arch cloud often presages a chinook. Because of the rapid temperature rises associated with a chinook, the arch has an important place in local weather lore as a predictor.
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chinook—The name given to the foehn in western North America, especially on the plains to the lee or eastern side of the Rocky Mountains in the United States and Canada. On the eastern slopes of the Rocky Mountains the chinook generally blows from the west or southwest, although the direction may be modified by topography. Often the chinook begins to blow at the surface as an arctic front retreats to the east, producing dramatic temperature rises. Jumps of 10°–20°C can occur in 15 minutes, and at Havre, Montana, a jump from −12° to +5°C in 3 minutes was recorded. Occasionally the arctic front is nearly stationary and oscillates back and forth over an observing station, causing the temperature to fluctuate wildly as the station comes alternately under the influence of warm and cold air. As in the case of any foehn, chinook winds are often strong and gusty. They can be accompanied by mountain waves, and they can occur in the form of damaging downslope windstorms. The air in the chinook originates in midtroposphere above the ridgetops, and its warmth and dryness result from subsidence. When moisture is present, a variety of mountain-wave clouds and lee-wave clouds can form, such as the chinook arch of the Canadian Rocky Mountains west of Calgary, Alberta. The chinook brings relief from the cold of winter, but its most important effect is to melt or sublimate snow: A foot of snow may disappear in a few hours. As with the foehn, researchers have attempted to classify chinooks as downslope winds with warming and boras as those accompanied by cooling. Again, these schemes have produced limited success because of the many ambiguous or erroneously classified cases.
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chinophile—Snow-loving; usually used to describe plants that have grown through a snow cover.
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chip log—A line marked at intervals [commonly about 15 m (50 ft)], and paid out over the stern of a moving ship. By timing the intervals at which the markers appear as the line is pulled out by a drag (the “chip”), the ship's speed can be determined. The wave length of ocean waves can be estimated by noting the position of wave crests relative to the markers.
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chlorine compounds—Any chemical compound containing chlorine (Cl), the 17th element in the periodic table. There are a number of chlorine-containing compounds found in the atmosphere, which are emitted from a variety of sources. Organic compounds containing chlorine are produced either via natural oceanic processes (e.g., methyl chloride) or for industrial purposes (e.g., chlorofluorocarbons). Some of these organic compounds are sufficiently long-lived to allow their transport to the stratosphere, where they are destroyed by photolysis. This process liberates chlorine atoms, which are active in the catalytic destruction of stratospheric ozone.
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chlorine dioxide—A highly reactive oxide of chlorine with chemical formula OClO. This species is of importance in the chemistry of polar stratospheric ozone depletion, as it is a product of the reaction of ClO with BrO. Its strong, structured absorption spectrum in the near-UV–visible region makes it extremely susceptible to destruction by photolysis, but also makes possible its detection via UV absorption in the atmosphere. Its detection in the antarctic ozone hole was one of the key discoveries that pointed to chlorine chemistry being the major cause of polar stratospheric mountain-wave cloud depletion. This compound should not be confused with the isomeric ClOO radical, which is thermally unstable (dissociating to Cl and O2).
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chlorine monoxide dimer—A chlorine compound with chemical formula Cl2O2. Its chemical structure is actually ClOOCl, and it is more properly known as dichlorine peroxide. This species plays a critical role in polar ozone destruction. Its formation (from recombination of two chlorine monoxide radicals in a termolecular reaction), followed by its subsequent photolysis to regenerate Cl atoms, is the major ozone depletion mechanism involved in the formation of the antarctic ozone hole.
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chlorine monoxide radical—A reactive radical species with chemical formula ClO. Chlorine monoxide is an important inorganic chlorine compound in the stratosphere. This species is produced in the reaction of Cl atoms with ozone. Its conversion back to Cl without reforming O3 (e.g., via reaction with O atoms) results in chlorine-catalyzed ozone loss in the stratosphere.
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