- 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 cold fall wind blowing from the northwest down the Vardar valley in Greece to the Gulf of Salonica. It occurs where atmospheric pressure over eastern Europe is higher than over the Aegean Sea, as is often the case in winter. It persists for two or three days with a mean velocity of 5–7 m s<sup>−1</sup>(10–15 mph), rising to 16 m s<sup>−1</sup> (35 mph) in squalls. It is strongest where the Vardar River leaves the mountains, but it extends for some distance out to sea. A similar wind, the Struma fall wind, blows in the Struma valley.
Industry:Weather
A cold fall wind blowing from the northwest down the Vardar valley in Greece to the Gulf of Salonica. It occurs where atmospheric pressure over eastern Europe is higher than over the Aegean Sea, as is often the case in winter. It persists for two or three days with a mean velocity of 5–7 m s<sup>−1</sup>(10–15 mph), rising to 16 m s<sup>−1</sup> (35 mph) in squalls. It is strongest where the Vardar River leaves the mountains, but it extends for some distance out to sea. A similar wind, the Struma fall wind, blows in the Struma valley.
Industry:Weather
The pressure exerted by the molecules of a given vapor. For a pure, confined vapor, it is that vapor's pressure on the walls of its containing vessel; for a vapor mixed with other vapors or gases, it is that vapor's contribution to the total pressure (i.e., its partial pressure). In meteorology, vapor pressure is used almost exclusively to denote the partial pressure of water vapor in the atmosphere. Care must be exercised in interpreting the term's meaning as used in other branches of science. See saturation vapor pressure, equilibrium vapor pressure.
Industry:Weather
A measurement of atmospheric conditions aloft, above the effective range of a surface weather observation. This is a general term, but is usually applied to those observations that are used in the analysis of upper-air charts (as opposed to measurements of upper-atmospheric quantities primarily for research). Among the elements evaluated are pressure, temperature, relative humidity (e.g., by radiosonde aircraft observations), and wind speed and direction (e.g., by rawinsonde, aircraft, or wind profiling radars). Also, some mountain stations are high enough and exposed enough so that their observations may be included in the upper-air network at their elevation. See Also meteorological rocket, radiosonde balloon.
Industry:Weather
A cyclonic circulation existing in the upper air; specifically as seen on an upper-level constant-pressure chart. This term is often restricted to such cyclones associated with relatively little cyclonic circulation in the lower atmosphere.
Industry:Weather
An anticyclonic circulation existing in the upper air. This often refers to such anticyclones only when they are much more pronounced at upper levels than at and near the earth's surface.
Industry:Weather
A basic sampling problem that arises when the unambiguous velocity sampling interval is less than the full range of naturally occurring velocities, causing the erroneous appearance of higher velocities within the sampling interval. This phenomenon occurs in Doppler velocity measurements when the maximum unambiguous velocity interval (±''V''<sub>max</sub>) is less than the full range of velocities being measured. Any true velocity, ''V'', appears within the interval from −''V''<sub>max</sub> to +''V''<sub>max</sub>, with the value ''V''′, which is related to the true velocity by ''V'' = ''V''′ ± 2''nV''<sub>max</sub> where ''n'' is an integer. Therefore a given measured velocity ''V''′ may be caused by many values of the true velocity ''V''. For example, suppose ''V''<sub>max</sub> = 25 m s<sup>−1</sup> and the measured velocity ''V''′ = −15 m s<sup>−1</sup>. Then the values of true velocity that could account for this measurement are the following: −15 m s<sup>−1</sup> (for ''n'' = 0); +35 or −65 m s<sup>−1</sup> (for ''n'' = 1); +85 or −115 m s<sup>−1</sup> (for ''n'' = 2); etc. In some instances the erroneous velocities can be recognized and ambiguities resolved by additional considerations, such as the requirement of spatial continuity of the velocity field. See Also aliasing, Nyquist frequency.
Industry:Weather
Generally, the wind speeds and directions at various levels in the atmosphere above the domain of surface weather observations, as determined by any of the methods of winds-aloft observation.
Industry:Weather
