- 行业: 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, ...
An atmospheric ion of size and mobility intermediate between the small ion and the large ion. Whereas small and large ions are readily detected in all localities, intermediate ions have been reported only in a limited number of cases. The mobility of this class of ions lies generally in the interval from 0. 01 to 0. 1 cm s−1 (V cm−1)−1. In general, the present understanding of the nature and origin of intermediate ions is limited.
Industry:Weather
An average height that is weighted by some other characteristic of the vertical profile. For example, the potential temperature profile in the stable boundary layer at night often has an exponential shape because the greatest cooling has occurred nearest the ground and the temperature change decreases with height. By finding the area under the potential temperature change curve and dividing by the temperature change at the surface, a height scale is obtained that is an integral measure of the depth of the stable boundary layer. For this particular example of an exponential profile, the integral depth corresponds to the e-folding depth of the profile.
Industry:Weather
An atmospheric model in which the hydrostatic approximation replaces the vertical momentum equation. This implies that vertical acceleration is negligible compared to vertical pressure gradients and vertical buoyancy forces, a good approximation for synoptic and subsynoptic scales of motion. Hydrostatic models have been successfully applied with horizontal resolutions as small as about 10 km, resolving even some mesoscale circulations. Global and regional weather prediction models have traditionally been hydrostatic models.
Industry:Weather
An approximation to turbulence that retains prognostic equations for mean variables (such as potential temperature and wind) as well as for some of the higher-order statistics including variance (such as turbulence kinetic energy or temperature variance) or covariance (kinematic fluxes such as for heat and momentum). Regardless of the statistical order of the forecast equations, other high-order statistical terms appear in those equations, the solutions of which require approximations known as turbulence closure assumptions. While usually considered more accurate than first-order closures (K-theory), higher-order closure solutions are computationally more expensive. Turbulence closures are often classified according to two attributes: the order of statistical closure, and the degree of nonlocalness. Common types of higher-order closure include (in increasing statistical order): one-and-a-half order closure (also known as k-ε closure), second-order closure, and third-order closure. All turbulence closures are designed to reduce an infinite set of equations that cannot be solved to a finite set of equations that can be solved approximately to help make weather forecasts and describe physical processes. See Reynolds averaging; compare zero-order closure, half-order closure.
Industry:Weather
An area of slightly grounded ice in the mouth of some ice streams. Typically an area of very low basal stress.
Industry:Weather
An apparatus used to study the production of ions in the atmosphere by cosmic ray and radioactive bombardment of air molecules. The chamber is an airtight container usually cylindrical in shape and 25–50 L in volume. An insulated electrode is centrally located in the chamber. In operation a potential is applied between the electrode and the chamber wall. The ions produced in the chamber are collected by the electrode and measured by an electrometer. Amplification of ions may occur as the result of gas multiplication.
Industry:Weather
An apparatus that counts the number of unit charges of electricity that are contained in a sampled volume of the atmosphere. The general procedure is to pass a sample of the atmosphere through a charged cylindrical condenser. The change in the potential across the condenser is a measure of the ionic charge contained in the sample volume. The change in potential depends upon such factors as the polarizing potential of the condenser, the mobility and charge of the ions, volume and length of the condenser, and sample flow rate. An ion counter is an ionization chamber in which there is no internal amplification by gas multiplication.
Industry:Weather
An announcement for a specific area that hurricane conditions (sustained winds of 64 knots/73 mph or higher) pose a threat within 36 hours. Residents are cautioned to take stock of their preparedness needs, but, otherwise, are advised to continue normal activities.
Industry:Weather
An air-launched balloon designed to be released in the eye of a tropical cyclone, float within the eye at predetermined levels, and transmit radio signals for RDF positioning.
Industry:Weather
