- 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 balloon used to carry a radiosonde aloft. Radiosonde balloons are larger than pilot balloons and ceiling balloons, are generally filled with hydrogen or helium to achieve lift, and burst at altitudes of about 30 km in daytime and 25 km at night.
Industry:Weather
A 2 × 2 matrix comprising four signal amplitudes that characterizes the scattering from a target in terms of a polarization basis. The basis is defined by two orthogonal vectors, for example, horizontal and vertical or right and left circular. The diagonal terms are the amplitudes of the copolarized signals corresponding to the two transmitted polarizations, and the off-diagonal terms are the amplitudes of the cross- polarized signals. Each term carries a double subscript that denotes the transmitted and received polarization. Compare covariance matrix.
Industry:Weather
A “forecast” in which one of a set of meteorological contingencies is selected on the basis of chance. The random forecast is often used as a standard of comparison in determining the degree of skill of another forecast method. Compare persistence forecast, probability forecast.
Industry:Weather
1. With respect to radiation, a single point in space emitting radiation. The radiation from such a source may be expressed as flux per unit solid angle (W sr<sup>−1</sup>). 2. In experimental studies of atmospheric turbulence and diffusion, a source of particulate matter from a single fixed point. There are continuous and instantaneous point sources. The analogous concepts of line source and plane source are also frequently encountered. 3. In hydrodynamics, a source of mass, that is, a singular point in the field where the equation of continuity fails.
Industry:Weather
1. With respect to a transverse electromagnetic wave, the correlation between two orthogonal components of its electric (or, equivalently, magnetic) field. If the ratio of the amplitudes of these two components and the difference in their phases is constant in time (completely correlated), the wave is said to be polarized (or completely polarized or 100% polarized). If these two amplitudes and phases are uncorrelated, the wave is said to be unpolarized (or 0% polarized). These are two extreme degrees of correlation, never strictly realized in nature, all real waves being partially polarized (or partially correlated). Associated with a polarized wave is its vibration ellipse traced out in time by the oscillating electric field at a given point in space. A line (circle) is a special ellipse, and a wave with such a vibration ellipse is said to be linearly (circularly) polarized, but the general state of (complete) polarization is elliptical. A vibration is characterized by its handedness (the sense in which it rotates; clockwise or counterclockwise), the ratio of its minor to major axis (ellipticity), and its orientation (azimuth). Any beam may be decomposed uniquely as an incoherent superposition of two beams, one unpolarized and one polarized. Thus, the ratio of the transmitted power of the polarized component to the total transmitted power may be taken as a measure of the degree of polarization of the beam. The vibration ellipse of the polarized component and the degree of polarization define the state of polarization of the beam. Polarization would be an uninteresting (indeed, unmeasurable) property of electromagnetic radiation were it not for the fact that two beams, identical in all respects except their state of polarization, may interact with matter differently. Skylight (for a molecular atmosphere) is, in general, partially linearly polarized, the degree of polarization being greatest approximately 90° from the sun. 2. With respect to particles in an electric field, the displacement of the charge centers within a particle in response to the electric force acting thereon. See polarizability.
Industry:Weather
1. Total quantity of sediment moving out of a watershed in a given time interval, expressed in units of mass per unit time. 2. Total sediment discharge from a watershed relative to the watershed area, expressed in units of mass per unit time per unit area.
Industry:Weather
1. Usually, same as total pressure. 2. Sometimes, same as dynamic pressure.
Industry:Weather
1. The thickest form of sea ice, one to several years old (perhaps paleocrystic), and sometimes more than 3 m (10 ft) thick. 2. (Also called polar-cap ice. ) The pack ice of the central Arctic Ocean.
Industry:Weather
1. The vapor pressure of a system, at a given temperature, for which the vapor of a substance is in equilibrium with a plane surface of that substance's pure liquid or solid phase; that is, the vapor pressure of a system that has attained saturation but not supersaturation. The saturation vapor pressure of any pure substance, with respect to a specified parent phase, is an intrinsic property of that substance, and is a function of temperature alone. For water vapor, the saturation pressure over supercooled liquid differs appreciably from that over ice. Compare equilibrium vapor pressure, vapor tension; See Clausius–Clapeyron equation. 2. Same as equilibrium vapor pressure.
Industry:Weather
1. The spontaneous transition of an atomic nucleus to a lower energy state (radioactive decay) accompanied by the emission of an alpha particle, a beta particle, or gamma radiation. Alpha emission results in a reduction of atomic number by two and mass number by four; (negative) beta emission results in an increase of atomic number by one but no change in mass number; in gamma emission, atomic number and mass number are unchanged. Several naturally occurring isotopes are radioactive, including carbon-14 and potassium-40, which reside in the human body. Radon (strictly, radon-222) is a natural radioactive gas originating ultimately from the radioactive decay of uranium-238. Artificial radioactivity, as opposed to natural radioactivity, is a consequence of bombardment of isotopes that are not radioactive with neutrons, protons, and other subatomic particles. See half-life. 2. (Often simply activity. ) Rate of decay of a radioactive isotope. The unit of radioactivity is the curie.
Industry:Weather
