- 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, ...
In clear-sky optics, the vertical plane defined by sun, zenith, and observer. The clear daytime sky's radiance, polarization, and chromaticity patterns are largely symmetric about the principal plane.
Industry:Weather
A rise in temperature of the stratosphere in the polar region in late winter resulting from enhanced propagation of energy from the troposphere by planetary-scale waves. Temperatures near 50 mb can increase by as much as 40°C in just a few days.
Industry:Weather
A rise in temperature of the stratosphere in the polar region in late winter resulting from enhanced propagation of energy from the troposphere by planetary-scale waves. Temperatures near 50 mb can increase by as much as 40°C in just a few days.
Industry:Weather
A halo in the form of a colored spot at the same angular elevation as the sun. The lunar counterpart is a paraselene. The most common parhelia are seen about 22° on either side of the sun. That angular distance increases from 22° when the sun is on the horizon to over twice that when the sun climbs to 60°. The sun side of a parhelion is reddish. The parhelia of 22° can be explained by refraction in hexagonal crystals falling with principal axes vertical. The effective prism angle is 60° when the sun is on the horizon, but this increases as the sun climbs, resulting in greater displacement of the parhelion.
Industry:Weather
A halo in the form of a colored spot at the same angular elevation as the sun. The lunar counterpart is a paraselene. The most common parhelia are seen about 22° on either side of the sun. That angular distance increases from 22° when the sun is on the horizon to over twice that when the sun climbs to 60°. The sun side of a parhelion is reddish. The parhelia of 22° can be explained by refraction in hexagonal crystals falling with principal axes vertical. The effective prism angle is 60° when the sun is on the horizon, but this increases as the sun climbs, resulting in greater displacement of the parhelion.
Industry:Weather
Group of five digits (IIiii) used in meteorological messages to identify the station of origin of an observation report. It consists of the block number (II), defining the area in which the station is located, and the station index number (iii). See international index numbers.
Industry:Weather
The trails of precipitation that emerge from the base of generating cells typically observed on time–height displays from vertically pointing radars. Snow trails are also commonly observed on range–height indicator displays. Snow trails emerge from a layer of convective instability that often exists in the middle or upper troposphere in widespread storms. Small convective cells developing within this layer produce the ice crystals that then fall to lower altitudes. The base of the convectively unstable layer is called the snow- generating level. The shape and vertical extent of the streamers depend on the vertical profiles of wind and relative humidity in the layer through which the precipitation falls.
Industry:Weather
A high that forms over the cold continental surfaces of subpolar latitudes, principally in Northern Hemisphere winter. These highs typically migrate eastward and equatorward.
Industry:Weather
The reduction of temperature of any liquid below the melting point of that substance's solid phase; that is, cooling beyond its nominal freezing point. A liquid may be supercooled to varying degrees, depending upon the relative lack of freezing nuclei or solid boundary irregularities within its environment, and freedom from agitation. This supercoolability of a substance with a crystalline solid form (as opposed to amorphous matter) stems from the unique energy transformations necessary for the formation of the first crystal nucleus, whereafter all adjacent liquid immediately becomes solid unless or until the latent heat released elevates the system's temperature sufficiently to arrest the process. It should be noted that the reverse process is not possible; a crystalline solid cannot be “superheated”; therefore, a substance's melting point is very conservative, only slightly dependent upon pressure. Supercooled clouds are quite common. In extreme cases, they have been observed at temperatures as low as −40°C (−40°F). The smaller and purer the water droplets, the more likely is supercooling. Compare supersaturation; See nucleation. (Note: The choice of terminology for this concept has been variable and controversial for many years, largely based on conceptual views of the prefixes super, sub, and under. Supercooling remains, however, the most frequently utilized term. )
Industry:Weather
In studies of the general circulation, the eddies are the departures of a field (e.g., temperature or relative vorticity) from the zonal mean of that field; the stationary eddies are the time-averaged, or time-invariant, component of the eddy field.
Industry:Weather
