- 업종: 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 parameter depending on static stability that describes the variation of the wind speed with height. The Deacon parameter β is defined by du/dz = Cz−β, where u is the wind speed, z the height, and C a constant.
Industry:Weather
The logarithmic scale for measuring radar reflectivity factor, referred to a value of 1 mm6 m−3, defined by
where Z is the reflectivity factor (mm6 m−3), Z1 is 1 mm6 m−3, and ζ is the reflectivity factor in dBZ. See decibel.
Industry:Weather
The number of days per month with snow cover on the ground. Typically expressed as the percentage of days per month that snow cover of various depths is on the ground for a location in categories from trace to whole inches.
Industry:Weather
1. A basic time increment defined by the earth's motion; specifically, a complete revolution of the earth about its own axis. The sidereal day is defined as the time required for the earth to make one complete revolution in an absolute coordinate system, that is, with respect to the stars. The day in common use is the mean solar day, derived, by means of the equation of time, from the apparent solar day, which is determined directly from the apparent relative motion of the sun and earth. The civil day is a modification of the mean solar day, which renders it practical as a time measure for ordinary purposes. See also year, lunar day. 2. The period from midnight to midnight, local civil time; that is, a civil day. 3. The period of daylight, as opposed to that of darkness. 4. See pendulum day. 5. See observational day.
Industry:Weather
The first light visible in the solar sky before sunrise or the time of that appearance. Dawn is synonymous with “daybreak” and the beginning of morning twilight. Twilight is not an antonym of “dawn,” although dusk is used this way in nontechnical language.
Industry:Weather
A dimensionless number (CdRe2; Cd = drag coefficient; Re = Reynolds number) used in computation of terminal fall velocity of a precipitation particle.
Industry:Weather
For marine applications, a base elevation used as a reference from which to reckon heights or depths. It is called a tidal datum when defined in terms of a certain phase of the tide. Tidal datums are local datums, referenced to fixed points (bench marks), and should not be extended into areas that have differing hydrographic characteristics without substantiating measurements.
Industry:Weather
A countercurrent of the Pacific Ocean running north along the west coast of the United States (from northern California to Washington to at least latitude 48° N) during the winter months.
Industry:Weather
Agreed-upon horizontal control surface used as a standard reference to which elevations are related.
Industry:Weather
The leader which, after the first stroke, typically initiates each succeeding stroke of a multiple-stroke flash lightning. (The first stroke is initiated by a stepped leader. )
The dart leader derives its name from its appearance on photographs taken with streak cameras. The dart leader's brightest luminosity is at its tip which is tens of meters in length, propagating downward at about 107 m s−1. In contrast to stepped leaders, dart leaders do not typically exhibit branching because the previously established channel's low gas density and residual ionization provide a more favorable path for this leader than do any alternative ones.
Industry:Weather
