- 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, ...
1. A form of energy transferred between systems, existing only in the process of transfer. 2. Same as enthalpy. Heat, used as a noun, is confusing and controversial in its scientific meaning. The differential of heat is considered imperfect in that its value depends on the process applied. In the thermodynamic definitions in this glossary, heat is avoided as a noun or adjective except where required by established use. The process of heating is, however, defined as the net absorption of internal energy by a system.
Industry:Weather
1. The line that circumscribes the earth and connects all points of highest mean annual temperature for their longitudes. The course of the heat equator varies with the arrangement of continents and ocean currents. It does not even approximately parallel the geographic equator, but ranges from about 20°N in Mexico to about 14°S latitude in Brazil. From West Africa to the East Indies, the heat equator lies north of the geographic equator; from New Guinea to 120°W longitude, it lies south of the geographic equator. 2. The approximate latitude of highest mean annual surface temperature (about 10°N).
Industry:Weather
1. The axis, or a portion thereof, of the broad trade-wind current of the Tropics. This axis is the dividing line between the southeast trades and the northeast trades (of the Southern and Northern Hemispheres, respectively). It is collocated with the ascending branch of the Hadley cell. At one time it was held that this was a convergence line along its entire extent. It is now recognized that actual convergence occurs only along portions of this line. For further discussion, see equatorial trough; see also intertropical front, doldrums. 2. Same as meteorological equator.
Industry:Weather
1. The axis, or a portion thereof, of the broad trade-wind current of the Tropics. This axis is the dividing line between the southeast trades and the northeast trades (of the Southern and Northern Hemispheres, respectively). It is collocated with the ascending branch of the Hadley cell. At one time it was held that this was a convergence line along its entire extent. It is now recognized that actual convergence occurs only along portions of this line. For further discussion, see equatorial trough; see also intertropical front, doldrums. 2. Same as meteorological equator.
Industry:Weather
1. In terrestrial magnetism, the angle through which a freely suspended magnet would dip below the horizon in the magnetic north–south meridional plane; one of the magnetic elements. At the aclinic line (dip equator) the inclination is zero; at either magnetic pole (dip pole) the inclination is 90°. 2. The angle between the plane of the satellite orbit and the earth's equatorial plane. An inclination angle of less than 90° is referred to as a prograde orbit, while an inclination angle greater than 90° is called a retrograde orbit.
Industry:Weather
1. In terrestrial magnetism, the angle through which a freely suspended magnet would dip below the horizon in the magnetic north–south meridional plane; one of the magnetic elements. At the aclinic line (dip equator) the inclination is zero; at either magnetic pole (dip pole) the inclination is 90°. 2. The angle between the plane of the satellite orbit and the earth's equatorial plane. An inclination angle of less than 90° is referred to as a prograde orbit, while an inclination angle greater than 90° is called a retrograde orbit.
Industry:Weather
A singular point in a streamline field that constitutes the intersection of a convergence line and divergence line. It is analogous to a col in the field of a single-valued scalar quantity.
Industry:Weather
1. The beat frequency used in heterodyne reception resulting from the combination of the received radio-frequency signal and a locally generated signal. The intermediate-frequency signal is usually the difference between the above signals and is employed to avoid the difficulty of the direct amplification of radio-frequency signals, which is technically more difficult to accomplish. 2. See IF signal.
Industry:Weather
(Symbol He. ) Lightest of the noble gases, atomic number 2, atomic weight 4. 003. It has an atomic mass of 4 (2 protons and 2 neutrons) and is a colorless, monatomic element. It is the sixth most abundant gas in dry air. Helium is very light, having a specific gravity referred to air of 0. 138. This element is unique in that its existence on the sun was recognized prior to its discovery on the earth. Spectroscopic discovery in 1868 by Janssen in the solar spectrum was followed by terrestrial detection in 1889 and chemical isolation in 1894 by Ramsay. Because helium is not flammable and has a lifting power 92% of that of hydrogen, it is widely used as the inflation gas for lighter-than-air craft and for meteorological balloons. Helium nuclei are identical to radioactive alpha particles and helium is formed as a product of radioactive decay of certain elements, particularly the uranium group. Consequently, helium is often associated with deep deposits of fossil oil or gas and is released on mining.
Industry:Weather
A colorless and odorless gaseous element, atomic number 1, atomic weight 1. 008; the lightest and apparently the most abundant chemical element in the universe. However, it is found only in trace quantities in the observable portion of our atmosphere, in the amount of only about 0. 00005% by volume of dry air. Hydrogen H2 has a molecular weight of 2. 0160 and specific gravity referred to air of 0. 0695. The low escape velocity of hydrogen, combined with absence of active generating mechanisms on the earth, holds its concentration to negligible amounts. Its concentration increases above altitudes of several hundred kilometers as a consequence of diffusive separation. At one time, hydrogen was commonly used for inflating meteorological balloons, but because of its dangerous combustibility, it has been replaced by helium.
Industry:Weather
