- 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 halo in which vertical and horizontal streaks of light extend from the sun. Most of those observed probably result from the combination of a parhelic circle and a sun pillar.
Industry:Weather
A halo in the form of a pillar of light extending above or below the sun and usually seen when the sun is low in the sky. It is explained by reflection by the sides of columnar ice crystals falling with their long axes horizontal. The term light pillar is sometimes used when the source of light is artificial, such as street lamps.
Industry:Weather
A halo in the form of arcs that appear outside the upper and lower tangent arcs to the halo of 22°. The columnar crystals have their long axes horizontal, which by itself would produce the tangent arcs, and a prism face horizontal. See minimum deviation, anthelic arcs.
Industry:Weather
A halo in the form of a faint, white, horizontal arc at the elevation of the sun. Small segments are more frequently seen than the complete circle. When caused by the moon, it is called the paraselenic circle. The parhelic circle is explained by reflection by the vertical faces of oriented ice crystals, such as the sides of large hexagonal plates, which also produce parhelia and paranthelia.
Industry:Weather
A halo in the form of a faint spot at the same angular elevation as the sun, but located in the vicinity of the anthelion (a point at the same elevation as the sun but on the opposite side of the sky). The one at 120° from the sun (60° from the anthelion) is explained by internal reflections in an oriented hexagonal plate crystal.
Industry:Weather
A halo in the form of a bright white spot as far below the horizon as the sun is above it. The subsun is explained by reflection by the horizontal faces of oriented ice crystals (e.g., large hexagonal plates). Such crystals are never perfectly horizontal with the result that the shape of the subsun changes slightly with solar elevation, being circular for high suns and increasingly teardrop-shaped for low suns.
Industry:Weather
A group of five. In climatology, it is applied to a period of five consecutive days. It is often preferred to the week for climatological purposes since it is an exact factor of the 365-day year.
Industry:Weather
A grid on which all of the variables are not predicted at all of the points but rather are interspersed at alternate points. Grids using certain types of staggering, such as between mass and the components of momentum in the horizontal, have been shown to possess superior numerical properties to those of unstaggered grids.
Industry:Weather
A generic term for any fraction that divides a collection of observations arranged in order of magnitude into two specific parts. Thus, the upper quartile is the quantile that separates the upper one-quarter from the lower three-quarters of the observations. See'' also'' percentile, decile.
Industry:Weather
A gravity wave consisting of a single elevation of finite amplitude that propagates without change of form. First described in 1844 by Scott Russell in a British Association Report, its existence is a result of a balance between nonlinearity, which tends to steepen the wave front in consequence of the increase of wave speed with amplitude, and dispersion, which tends to spread the wave front as the wave speed of any spectral component decreases with increasing wavenumber. Most extensively studied are solitary waves on the free surface of a homogeneous, nonrotating fluid of finite depth. Surface solitary waves are also the easiest to observe. However, there also exist internal solitary waves, as the balance between nonlinearity and dispersion may be possible in the absence of a free surface by virtue of any or all of stratification, shear, compressibility, and rotation. See'' also'' envelope soliton.
Industry:Weather
