- 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, ...
Lowest temperature recorded between sunset and sunrise.
Industry:Weather
The lowering of temperature during nighttime, due to a net loss of radiant energy. See radiational cooling.
Industry:Weather
The cool layer of air adjacent to the ground that forms at night. At night under clear skies, radiation to space cools the land surface, which in turn cools the adjacent air through processes of molecular conduction, turbulence, and radiative transfer. This causes a stable boundary layer to form and grow to depths of a few hundreds of meters, depending on the season. Many interacting processes can occur within the statically stable nocturnal boundary layer: patchy sporadic turbulence, internal gravity waves, drainage flows, inertial oscillations, and nocturnal jets.
Industry:Weather
Thin silvery-blue cirrus-like clouds frequently seen during summer twilight conditions at high latitudes (above 50°) in both hemispheres. They are the highest visible clouds in the atmosphere, occurring in the upper mesosphere at heights of about 85 km, and are closely related to the polar mesospheric clouds seen in satellite observations at similar altitudes over the summer polar cap. Noctilucent clouds are now known to consist of tiny ice particles with dimensions of the order of tens of nanometers, growing in the extreme cold of the summer polar mesopause region. The condensation nuclei on which the particles grow are thought to be either smoke and dust particles of meteoric origin or large hydrated positive ions. Strong upwelling of air from below, associated with a pole-to-pole meridional circulation in the upper mesosphere, is responsible for both the extreme cold and the upward flux of water vapor. Although water-vapor mixing ratios are very low (less than 10 parts per million by volume) in the region, the temperatures are also low enough to produce a high degree of supersaturation at times. Anomalously strong radar echoes from the region, known as polar summer mesospheric echoes, are also associated with the clouds. Compare nacreous clouds, polar stratospheric clouds.
Industry:Weather
A system of mechanics based on Newton's laws of motion. The salient characteristics of Newtonian mechanics are that mass and energy are separately conserved, all physical variables can take on a continuous set of values, the state of a system at any instant uniquely determines its state at any later instant (determinism), and interactions at a distance are instantaneous. Compare quantum theory.
Industry:Weather
The elements helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) that make up the eighth period of the periodic table. Because of their completely filled atomic orbitals, these gases are extremely nonreactive, and build up to measurable concentrations in the atmosphere.
Industry:Weather
Colorless gas, formula N<sub>2</sub>O, released by bacterial activity at the earth's surface. It has an atmospheric lifetime of about 160 years and is currently present at a level of about 330 ppb. Its atmospheric significance is that it is transported into the stratosphere, where its reaction with excited oxygen atoms (O<sup>1</sup>D) is the major source of active nitrogen; it is also a major greenhouse gas. In large amounts, it has anesthetic properties (laughing gas).
Industry:Weather
1. Weak acid formed in solution by neutralization of the nitrite ion. Also formed when nitrogen dioxide, NO<sub>2</sub>, dissolves in water. 2. Gaseous compound, formula HONO, that builds up in polluted, typically urban air, containing nitrogen oxides. The only known gas-phase reaction leading to its formation, that between hydroxyl radicals (OH) and nitric oxide (NO), is not rapid enough to account for observed levels, and the formation is thus thought to involve particles. Nitrous acid photodissociates to give OH + NO, and can thus serve as an OH source, particularly in the early morning.
Industry:Weather
