| Section C | C index | 111-119 of 1157 terms |
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carrier—The unmodulated fundamental output of a radio or radar transmitter, which is capable of being modulated with information to produce a communications signal.
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carry-over—1. The portion of the streamflow during any month or year derived from precipitation in previous months or years. 2. Storage of water during a wet surplus year used for making up deficiencies in dry years.
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Cartesian coordinates—A coordinate system in which the locations of points in space are expressed by reference to three planes, called coordinate planes, no two of which are parallel. The three planes intersect in three straight lines, called coordinate axes. The coordinate planes and coordinate axes intersect in a common point, called the origin. From any point P in space three straight lines may be drawn, each of which is parallel to one of the three coordinate axes; each of these lines will then intersect one (and only one) of the three coordinate planes. If A, B, C denote these points of intersection, the Cartesian coordinates P are the distances PA, PB, and PC. If the coordinate axes are mutually perpendicular, the coordinate system is rectangular; otherwise, oblique. In meteorology, the most common orientation of the x, y, z rectangular Cartesian coordinates is such that the x axis is directed toward the east, tangent to the earth's surface; the y axis toward the north, tangent to the earth's surface; and the z axis toward the local zenith, perpendicular to the earth's surface. Compare curvilinear coordinates.
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Cartesian tensor—A quantity specified by components that transform according to prescribed rules under rotations of (Cartesian) coordinate axes. A Cartesian tensor of rank zero is a scalar and is invariant under rotations. A Cartesian tensor of rank one is a vector, the components of which transform under rotations according to a single 3×3 rotation matrix. Cartesian tensors of rank two have nine components that transform according to a product of two 3×3 rotation matrices. Tensors of higher rank may be defined in similar fashion. As examples related to meteorology, mass is a scalar, velocity is a vector, and the stress tensor is a Cartesian tensor of rank two. [Because of the restriction to transformation under rotation, a Cartesian tensor need not be a (general) tensor. The latter has components that transform in a prescribed way under arbitrary changes of coordinates.]
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cascade impactor—A low-speed impaction device consisting of a set of impactor plates connected in series or in parallel for use in sampling both solid and liquid particles suspended in the atmosphere. The diameters of the nozzles or slits above each impactor plate are designed in such a manner that each sampling plate collects particles of predominantly one size range. This method is used to obtain different size fractions of ambient particles in the range of diameters ∼ 0.5 to 30 μm.
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cascade shower—(Also air shower, cascade, extensive air shower, shower.) Multiple generations of secondary cosmic rays produced when primary cosmic rays interact with atoms in the upper atmosphere, yielding subatomic particles and gamma rays. The secondary cosmic rays in turn produce even more down through the atmosphere. Billions of these particles travel downward at nearly the speed of light and at ground level may extend over several square kilometers (in which instance the shower may be termed an extensive air shower). The maximum flux of cosmic rays, both primary and secondary, is at an altitude of 20 km, and below this the absorption by the atmosphere reduces the flux, though the rays are still readily detectable at sea level. Intensity of cosmic ray showers has also been observed to vary with latitude, being more intense at the poles.
Friedlander, M. W., 1989: Cosmic Rays, pp. 13, 79.
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