| Section A | A index | 551-559 of 917 terms |
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annual minimum series—In hydrology, a series of data consisting of the smallest values for each year.
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annual range—Within a prescribed annual period, the difference between the maximum and the minimum value of a given set of numbers or of a temporally varying function. See range.
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annual runoff—Total volume of water that is discharged from a drainage area (watershed or catchment) and measured at a specified point on a stream or river during a year.
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annual series—In hydrology, a series of data consisting of one value of a given parameter for each year.
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annual storage—The storage capacity of a reservoir required to smooth out seasonal fluctuations in streamflow within a year.
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anomalous propagation—(Sometimes abbreviated AP or anaprop.) A propagation path of electromagnetic radiation that deviates from the path expected from refractive conditions in a standard atmosphere. In standard propagation conditions, radiation transmitted horizontally at the earth's surface is bent downward along a path with a radius of curvature equal to 4/3 times the radius of the earth. Subrefractive propagation causes less bending of the ray and superrefractive propagation causes greater downward bending than in the standard conditions. AP clutter is an extended region of ground echoes caused by superrefraction. See effective earth radius.
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anomalous refraction—Literally, refraction that is not normal or typical. Anomalous or abnormal is frequently used to characterize the conditions that give rise to mirages, such as in this example: “Abnormal refraction responsible for mirages is invariably associated with abnormal temperature distributions that yield abnormal spatial variations in the refractive index.” Yet mirages and the conditions that give rise to them are very common. It would appear that, when these terms are used, normality is something defined by the free atmosphere, far from surfaces. Certainly, by that measure, the refractive index gradients near a surface are abnormal. It is misleading to imply that either the refractive structures or the mirages are abnormal or anomalous when they are so common near the earth's surface, merely because they are not as common farther away from that surface.
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anomalous—Not encompassed by rules governing the majority of cases; distinguished from abnormal by implying a difference of kind rather than a difference merely of degree. This distinction between anomalous and abnormal is not strictly recognized in meteorology. As an example, a weather anomaly often implies a difference of degree.
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