- 行业: Weather
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The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, AMS has a membership of more than 14,000 professionals, ...
A rainbow that is distinguished from other rainbows by its angular radius, color order, and brightness. This bow is seen between about 40° and 42° from the antisolar point (shadow of the observer's head) or equivalently, between 140° and 138° from a light source (such as the sun). Reds are found to the outside of the bow (closest to the sun) with the blues to the inside. The primary bow is usually brighter than any of the other bows. The primary rainbow is certainly the most frequently noticed bow, but the purity and range of its colors fall a long way short of that assumed by the popular dictum: all the colors of the fall. Frequently accompanying the primary bow are the secondary bow (lying about 8° outside the primary bow) and the supernumerary bows (immediately inside the primary bow, and often confined to the upper portions of the arc). Infrequently seen are the reflection bows. A theory of the bow that approximates the behavior of light as a ray is able to account for the difference in position and color order of the primary and secondary bows. In this theory, the position of each bow is determined by the minimum angle of deviation of the light passing through a drop. The difference is that the light that forms the primary bow has undergone one internal reflection, while the light that forms the secondary bow has undergone two internal reflections. This is a useful approximation to reality, but it fails to capture many important features of observable bows. Compare secondary rainbow.
Industry:Weather
A rainbow formed by a light source reflected by an extended water surface; not to be confused with a rainbow seen reflected in a still body of water. When the water is calm, the center of a reflection rainbow is at the same elevation as the sun but in the opposite part of the sky. Such a bow intersects the ordinary rainbow (primary or secondary) at the horizon. When the water is rough (which it often is under the windy conditions in the vicinity of a shower) a family of reflection bows is formed, the envelope of which produces an essentially vertical bow, which intersects the ordinary bow at the horizon.
Industry:Weather
A radiometric term for the rate at which radiant energy in a set of directions confined to a unit solid angle around a particular direction is transferred across unit area of a surface (real or imaginary) projected onto this direction. Unlike irradiance, radiance is a property solely of a radiation field, not of the orientation of the surface. The SI units of radiance are W m<sup>−2</sup> sr<sup>−1</sup>. In general, radiance depends on time, position, and direction as well as frequency (monochromatic or spectral radiance) or range of frequencies. Irradiance for any surface is the integral of radiance over a hemisphere of directions above or below that surface. The photometric equivalent of radiance is luminance, obtained by integrating spectral radiance weighted by luminous efficiency over the visible spectrum.
Industry:Weather
A radiometer that used a rotating or an oscillating plane mirror to scan a path normal to the movement of the instrument.
Industry:Weather
A radio or radio-facsimile HF broadcast covering a high-seas oceanic area.
Industry:Weather
A radio or radio-facsimile broadcast covering a region or part of an ocean basin such as an offshore forecast area or the Gulf of Mexico.
Industry:Weather
A radio broadcast covering an area smaller than that of a regional broadcast.
Industry:Weather
A radar that transmits and receives individual pulses of radio energy, as opposed, for example, to a continuous-wave radar. The range to a target is measured by the time for a pulse to travel from the transmitter out to the receiver and back.
Industry:Weather
A radar capable of measuring polarization-dependent attributes of a target. McCormick and Hendry (1975) used this term to describe a radar that transmits a fixed (or slowly variable) polarization while receiving signals of identical and orthogonal polarization. The term is equivalent to dual-channel radar. Compare dual-polarization radar, polarimetric radar.
Industry:Weather
A radar capable of measuring any or all of the polarization-dependent attributes of a target or backscattering medium. The term may denote a radar capable of measuring the full polarization matrix by means of variable transmitted polarization and dual-channel reception. It may also denote a simpler radar that transmits a single polarization and receives separately the copolarized and cross-polarized components of the returned signal. Compare dual-channel radar, dual-polarization radar, polarization-diversity radar.
Industry:Weather
