- 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 forecast for a period greater than seven days in advance, although there are no absolute limits to the period embraced by the definition. Compare medium-range forecast, extended forecast.
Industry:Weather
A float that is used to obtain Lagrangian (following a fluid particle, thus drifting) current measurements. See Swallow float, drifter.
Industry:Weather
A finite-difference approximation to a time evolution equation in which the time derivative is approximated with values one time step before and one time step ahead of the values that specify other terms of the equation. The scheme (fn + 1 − fn − 1)/2Δt = g(fn) (where superscript n denotes a point in time, separated by step Δt from the prior (n − 1) and subsequent (n + 1) discrete time levels) is a leapfrog approximation to the differential equation df/dt = g(f). Compare implicit time difference.
Industry:Weather
A dry foehnlike wind from southeast or south in Cheribon and Tegal in Indonesia. It is caused by the east monsoon that develops a jet effect in passing through the gaps in the mountain ranges and descends on the leeward side.
Industry:Weather
A differential equation that is linear in the dependent variable and derivatives thereof. The existence of a wealth of mathematical techniques and tables for the treatment of linear equations guarantees that a physical problem representable by such an equation is very much easier to solve and understand than a nonlinear one. The advection terms in the fundamental equations of hydrodynamics are not linear (strictly, they are “quasi-linear”), and much of dynamic meteorology has been an attempt to circumvent this difficulty.
Industry:Weather
A differential equation that has been derived from an original nonlinear equation by the treatment of each dependent variable as consisting of the sum of an undisturbed or steady component and a small perturbation or deviation from this mean. It is assumed that the product of two perturbation quantities is negligible compared to the first-order terms in the perturbations or to the undisturbed variables. This process of linearization, often called the method of small perturbations, leads to a linear differential equation with the perturbations of the original dependent variables as the new dependent variables. It has been used successfully to solve problems involving sound waves, gravity waves, frontal waves, tides, waves in the upper westerlies, and flow over hills and mountains.
Industry:Weather
A differential equation solved numerically by a method of successive approximations that fits the solution to given boundary conditions. Elliptic equations, such as the Poisson equation, lead to jury problems. A partial differential equation, such as the barotropic vorticity equation, may combine a jury problem and a marching problem.
Industry:Weather
A diagnostic equation, based on thermal wind balance, with a solution consisting of meridional cell circulations that are forced by eddy fluxes of heat and momentum and by diabatic processes.
Industry:Weather
A device that operates on radar principles but that uses a laser as its source of transmitted light-frequency (ultraviolet, visible, or infrared) energy, instead of radio-frequency sources. See lidar.
Industry:Weather
A device for physical simulation of the atmosphere, using water or other liquids as the working fluid. Classical examples are 1) rotating tanks colloquially called dishpans, to simulate long waves in the general circulation; 2) turbulence tanks to simulate boundary layer evolution and convective thermals; and 3) towing tanks to simulate pollutant dispersion associated with mean flow about an obstacle. Because of tank size limitations and the characteristics of water compared to air, not all atmospheric flows can be simulated, and care must be taken to scale or nondimensionalize the results to make them independent of the working fluid. Compare large eddy simulation models, direct numerical simulation.
Industry:Weather
