- 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 type of spectral hygrometer using at least two closely spaced wavelengths. One is chosen inside an absorption band, the other outside and not affected by water vapor absorption. Subtraction of the latter measurement from the first cancels all absorption effects except that by the water vapor. Despite this simple principle the technical realization is difficult due to the need for adjusting and maintaining the two wavelengths very precisely. Instruments based on this technique are differential absorption lidars operating on two fixed wavelengths, or, as a recent development, tunable diode lasers. The wavelength of these lasers can be changed or tuned continuously over a small wavelength range allowing for monitoring the shape and intensity of a whole absorption line and its vicinity.
Industry:Weather
More or less a synonym for electrical insulator, a material with a low (compared with that of a metal) electrical conductivity. The term insulator is more precise given that at some frequencies the relative permittivity (or dielectric function) of a material usually described as an insulator may have values thought to be characteristic of metals, and at other frequencies the relative permittivity of a metal may have values thought to be characteristic of a dielectric (insulator).
Industry:Weather
A measure of the resistance of a dielectric to electrical breakdown under the influence of strong electric fields; usually expressed in volts per meter. The dielectric strength of dry air at sea level pressures is about 3 000 000 V m−1. The exact value for air depends upon geometry of the electrodes between which the electric field is established, upon the humidity, and upon whether or not water drops are present in the air.
Industry:Weather
The daily cycle. Diel is sometimes used by soil micrometeorologists and atmospheric chemists in place of the word diurnal.
Industry:Weather
Mixing in a diapycnal direction, that is, mixing of fluid from one side of an isopycnal surface with different (potential) density fluid from the other side of the surface.
Industry:Weather
Two different imaginary parts of the refractive index for electromagnetic waves identical except for their states of (orthogonal) polarization. By orthogonal is meant that the waves have opposite handedness, the same ellipticity, and the major axes of their vibration ellipses are perpendicular to each other. The most general dichroism is elliptical, specific examples of which are linear and circular. The dichroism of a medium originates from its asymmetry. See birefringence.
Industry:Weather
In a direction normal to the local isopycnal surfaces. Since isopycnal surfaces are close to horizontal, the diapycnal direction is close to vertical. The velocity of water normal to isopycnal surfaces is called diapycnal velocity, and the fluxes of properties perpendicular to an isopycnal surface are called diapycnal fluxes.
Industry:Weather
Small ice crystals falling from an apparently cloudless sky, (often, but not always, at night). Crystals originate from air having a higher moisture content above a thermal inversion aloft, where mixing leads to nucleation and growth of crystals at temperatures near −40°C.
Industry:Weather
Any equation governing a system that contains no time derivative and therefore specifies a balance of quantities in space at a moment of time (e.g., hydrostatic equation, balance equation). Compare prognostic equation.
Industry:Weather
A thermodynamic change of state of a system in which the system exchanges energy with its surroundings by virtue of a temperature difference between them. Compare adiabatic process.
Industry:Weather
