- 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, ...
Typically used to denote that a forecast is free from any direct subjective influences resulting from human experience, interpretation, or bias. Examples are numerical and statistical forecasts. See subjective forecast.
Industry:Weather
An analysis that is free from any direct subjective influences resulting from human experience, interpretation, or bias. See objective forecast.
Industry:Weather
A night wind from mountains or the upper ends of lakes; a wind of Salzkammergut in Austria.
Industry:Weather
Evaporative cooling effect due to heat advection when a source of water exists in an otherwise arid area. In addition to true desert oases, the oasis effect is also characteristic of natural bodies of water in arid surroundings, melting snow patches, irrigated fields in arid areas, or irrigated urban lawns and parks. Latent heat flux from such an oasis can exceed the locally available radiative flux twofold; advection of sensible heat from surrounding warmer surfaces and airmass subsidence over the cooler area provides the remainder. Evaporation also exceeds the local precipitation, the extra water coming from wells, river flow, and irrigation.
Industry:Weather
A numerical integration in which the goal is typically to study the behavior of the solution without regard to the initial conditions (to distinguish it from a numerical forecast). Thus the integrations are usually for extended periods to allow the solution to become effectively independent of the initial conditions.
Industry:Weather
In oceanography, the prediction of flow evolution via numerical construction of approximate solutions to the governing equations. Solutions are obtained by assigning discrete values to temporal and spatial derivatives in order to convert the governing differential equations into algebraic equations that can be solved by using computational methods. Because computational resources are finite, no one technique is ideal for all applications. Some models define the equations on very fine spatial intervals (see direct numerical simulation). This approach furnishes solutions that are very accurate, but that span only small spatial regions (spatial scales of a few meters, at present). At the other extreme, some models span entire ocean basins by using large spatial intervals (hundreds of kilometers). Here, approximation of unresolved motions is a crucial and difficult issue (see very large eddy simulation). Similar trade-offs must be made with respect to temporal solutions. Numerical models also differ in the equations and boundary conditions that are employed. The most general model commonly used in oceanography includes momentum conservation via the incompressible Navier–Stokes equations with the Boussinesq approximation, mass conservation via the incompressibility condition, and equations expressing conservation of heat energy and salt (e.g., Gill 1982). For large-scale applications, the hydrostatic approximation is usually made. The vertical coordinate may be the geometric height, or a convenient substitute such as density, pressure, logarithm of pressure, or potential temperature. Surface boundary conditions generally express fluxes of momentum, heat, and freshwater from the atmosphere. Basin-scale models use boundary conditions that approximate the effects of bottom topography. Smaller-scale models typically specify periodic conditions at the side boundaries and an energy radiation condition at the bottom. See also column model, mixed layer models, coupled model.
Industry:Weather
A four-dimensional data assimilation method that uses dynamical relaxation to adjust toward observations (observation nudging) or toward an analysis (analysis nudging). Nudging is accomplished through the inclusion of a forcing term in the model dynamics, with a tunable coefficient that represents the relaxation time scale. Computationally inexpensive, nudging is based on heuristic and physical considerations.
Industry:Weather
1. The positively charged core of an atom about which its electrons orbit. Almost all the mass of an atom resides in its nucleus, the diameter of which is about 10<sup>4</sup> times smaller than that of the atom. The nucleus of an (electrically neutral) atom is made up of protons, equal in number to its electrons, and neutrons bound together by nuclear forces. 2. In physical meteorology, a particle of any nature that initiates a phase transition in an environment supersaturated or supercooled with respect to a phase with lower chemical (Gibbs) potential, for example, a solid or liquid particle or gas/vapor bubble in a supercooled/supersaturated environment. See Aitken nucleus.
Industry:Weather
1. Any of several devices for determining the number of condensation nuclei or ice nuclei in a sample of air. 2. Same as dust counter.
Industry:Weather
