- Settore: 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, ...
An instrument developed by John Aitken for determining the dust content of the atmosphere. A sample of air is mixed in an expandable chamber with a larger volume of dust-free air containing water vapor. Upon sudden expansion, the air in the chamber cools adiabatically below its dewpoint, and droplets form with the dust particles as nuclei. A portion of these droplets settle on a ruled plate in the instrument and are counted with the aid of a microscope. See dust counter.
Industry:Weather
A transverse wave propagating along a magnetic field in an electrically conducting fluid (or plasma). This kind of wave does not exist in gases or fluids that are not ionized or in a plasma free from a magnetic field. The dynamics of such waves are analogous to those in a vibrating string.
Industry:Weather
The dark region of the sky seen between the primary and secondary rainbows. It is named after Alexander of Alphrodisias, the first person known to have commented upon it. He was the head of the Lyceum from 198 to 211 A. D.
Industry:Weather
A low pressure system that is often fast-moving, has low moisture content, and originates in western Canada (in or near Alberta province). In the wintertime, it may be associated with a narrow but significant band of snowfall, and typically affects portions of the plains states, Midwest, and East Coast.
Industry:Weather
The low pressure center located near the Aleutian Islands on mean charts of sea level pressure. It represents one of the main centers of action in the atmospheric circulation of the Northern Hemisphere. The Aleutian low is most intense in the winter months; in summer it is displaced toward the North Pole and is almost nonexistent. On a daily basis, the area of the Aleutian low is marked by alternating high and low pressure centers, moving generally to the eastward; it is not the scene of an intense stationary low. Normally the depth of intensity of the low pressure areas exceeds the intensity of the high pressure areas, so that the region is one of low pressure on the average. The travelling cyclones of subpolar latitudes usually reach maximum intensity in the area of the Aleutian low. The Aleutian low and its counterpart in the Atlantic Ocean, the Icelandic low, compose the Northern Hemisphere's subpolar low pressure belt.
Industry:Weather
The southern, eastward flowing current of the subpolar gyre in the North Pacific. It is fed by the outflow from the Oyashio and lies north of the North Pacific Current, with which it establishes the polar front in the west and experiences much water exchange as it proceeds eastward. As it approaches the coast of North America, it divides to form the northward flowing Alaska Current and the southward flowing California Current.
Industry:Weather
Very reactive organic compounds that contribute to local and regional ozone production, and also act as the precursors of peroxyacetyl nitrates. Their major atmospheric fate is reaction with hydroxyl radicals or photolysis.
Industry:Weather
A low that originates centered on the eastern slope of the Canadian Rockies in the province of Alberta, Canada. Formerly, it was thought that such lows actually originated (more or less independently) over this location. It is now recognized that depressions moving inland from the Pacific are the actual parent systems. Alberta lows appear as these systems enhance, or are enhanced by, the dynamic trough that is a typical, almost semipermanent, feature of this region.
Industry:Weather
An instrument used for the measurement of the reflecting power (the albedo) of a surface. A pyranometer adapted for the measurement of radiation reflected from the earth's surface is sometimes employed as an albedometer.
Industry:Weather
The ratio of reflected flux density to incident flux density, referenced to some surface. Albedos commonly tend to be broadband ratios, usually referring either to the entire spectrum of solar radiation, or just to the visible portion. More precise work requires the use of spectral albedos, referenced to specific wavelengths. Visible albedos of natural surfaces range from low values of ∼0. 04 for calm, deep water and overhead sun, to > 0. 8 for fresh snow or thick clouds. Many surfaces show an increase in albedo with increasing solar zenith angle. See also plane albedo, planetary albedo, spherical albedo, directional-hemispherical reflectance, bihemispherical reflectance.
Industry:Weather
