- Industry: Weather
- Number of terms: 60695
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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, ...
The weather radar, sometimes called NEXRAD, that became the operational network radar for the U. S. National Weather Service, U. S. Air Force, and Federal Aviation Administration during the early and middle 1990s. It is a general-purpose weather radar with a wavelength of 10. 5 cm, a peak power of 750 kW, selectable pulse duration of 1. 57 or 4. 0 μs, and selectable pulse repetition frequency from 318 to 1304 Hz. A coherent Doppler radar, it employs a center-fed parabolic antenna with a diameter of 8. 5 m, producing a beamwidth of 0. 95°. Received signals are analyzed using the method of pulse-pair processing to give as fundamental data the reflectivity factor, mean Doppler velocity, and Doppler spread as functions of time and location relative to the radar. The maximum unambiguous range is ordinarily 460 km for reflectivity and 115 km for Doppler information. Many kinds of computer algorithms are employed for identifying features such as vortices, downbursts, and fronts.
Industry:Weather
A hypothesis for the amplification of certain atmospheric circulations, including tropical cyclones, polar lows, and the Madden– Julian oscillation. The mechanism involves a positive feedback between the circulation and heat fluxes from the sea surface, with stronger circulation giving rise to larger surface fluxes of heat, which are then quickly redistributed aloft by convection, in turn strengthening the circulation. In this theory, emphasis is placed on the surface fluxes as the principal rate-limiting process; convection serves only to redistribute heat. This can be contrasted with conditional instability of the second kind (CISK), in which circulations amplify through their interaction with the convection itself.
Industry:Weather
Time–height profile of horizontal wind vectors derived from a scanning Doppler radar using a velocity–azimuth display (VAD) algorithm.
Industry:Weather
A region of weak radar echo that is bounded on one side and above by strong echo. It is located on the low-altitude inflow side of the storm. The WER is produced by strong updraft that carries precipitation particles to midlevels in a convective storm before they grow to radar-detectable sizes. In identifying a WER with radar, care must be taken to ensure that the strong midlevel echo is related to an updraft and not to horizontal motion of precipitation particles (e.g., the spreading anvil). See Also bounded weak echo region (BWER).
Industry:Weather
The primary meteorological sensor providing imaging functions on the SMS and early GOES satellites.
Industry:Weather
A modeling technique in which spatial resolution covers part, but not all of the energy-containing subrange. Most large-scale ocean (and atmosphere) models fall into this category.
Industry:Weather
A set of regulations set down by the U. S. Civil Aeronautics Board (in Civil Air Regulations) to govern the operational control of aircraft during visual flight. The abbreviation VFR is seldom used to denote the regulations themselves, but is popularly used to describe the weather and/or flight conditions to which these rules apply.
Industry:Weather
A radar display of the mean Doppler velocity at a given range as a function of the azimuth angle as the radar antenna rotates through (usually) a complete 360° azimuth scan at a constant elevation angle. Harmonic analysis of a VAD is used to determine spatially averaged kinematic properties of the wind field, namely, the wind speed and direction, the horizontal divergence, the horizontal deformation, and the orientation of the axis of dilatation. By repeating this process at many elevation angles or ranges, a vertical profile of the horizontal wind (VAD wind profile) above the radar site can be constructed.
Industry:Weather
An advanced version of the VISSR instrument that provided atmospheric sounding functions in addition to imaging functions. VAS was flown on ''GOES''''-4'' through ''-7''.
Industry:Weather
