| Section A | A index | 531-539 of 917 terms |
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angular drift—“Rock debris formed by intensive frost action, derived from underlying or adjacent bedrock. Contrast with glacial drift.” [Glossary of Arctic and Subarctic Terms (1955).]
Arctic, Desert, Tropic Information Center (ADTIC) Research Studies Institute, 1955: Glossary of Arctic and Subarctic Terms, ADTIC Pub. A-105, Maxwell AFB, AL, 90 pp.
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angular-momentum balance—An integral requirement for a system that is characterized by conservation of angular momentum. A description of the angular-momentum balance of a physical system includes 1) a description of the partition of absolute angular momentum within the system, and 2) a description of the mechanism by which absolute angular momentum is transferred from one portion of the system to another and also between the system and its surroundings. See also angular momentum, local angular momentum.
Gill, A. E., 1982: Atmosphere–Ocean Dynamics, Academic Press, 583–587.
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angular momentum—In Newtonian mechanics the angular momentum (or moment of momentum) L about a point O of a body with linear momentum p is the vector cross product  where r is the position vector of the body relative to O. In the absence of a net torque, angular momentum is conserved. But angular momentum is a more fundamental quantity than that defined by this equation. For example, photons have intrinsic angular momenta (spin), which can be transferred to objects (as evidenced by radiation torque), and yet the photon has zero rest mass. Thus, angular momentum is best looked upon as a single entity, complete in itself, governed by the dynamical law  where N is the torque acting on the body with angular momentum L. In meteorology, it is conventional to deal with angular momentum per unit volume, which is given by the product r × V, where is the density and V the velocity. Compare momentum, relative angular momentum, absolute angular momentum.
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angular resolution—In radar meteorology: 1) for point targets, the minimum angular separation at the antenna for which two targets at the same range can be distinguished; 2) for distributed targets, the minimum angular separation at the antenna for which distinct features (such as reflectivity cores) of the distributed targets can be distinguished. The angular resolution is usually taken to be the 3-dB beamwidth.
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angular-spreading factor—In early ocean wave forecasting methods, the fraction by which the estimated energy of waves leaving the generation area is multiplied to obtain the forecast wave energy at a distant point, after reduction due to angular spreading.
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angular velocity of the earth—The angular velocity of the earth (in the absolute coordinate system) is directed along the earth's axis toward the pole star and is equal in magnitude to 7.2921 × 10−5 rad s−1.
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angular velocity—The rate of rotation of a particle about the axis of rotation, with magnitude equal to the time rate of angular displacement of any point of the body. Angular velocity is a vector oriented in accordance with a right-hand rotation (i.e., when the fingers of the right hand are curved in the sense of rotation, the thumb points in the direction of the angular velocity vector).
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angular wavenumber—(Also called azimuthal wavenumber, hemispheric wavenumber, zonal wavenumber.) In many meteorological contexts, the number of waves of a given wavelength required to encircle the earth at the latitude of the disturbance. If L is the wavelength, r the earth's radius, and φ the geographical latitude, the angular wavenumber k is given by k = 2πrcos φ/L. Compare wavenumber.
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