- 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 vorticity as measured in a system of coordinates fixed on the earth's surface. Usually, only the vertical component of the vorticity is meant. See'' also'' geostrophic vorticity, vorticity equation.
Industry:Weather
A diffuse, but sometimes fairly bright, illumination of those parts of a thundercloud that surround the path of a lightning flash, particularly a cloud discharge or cloud-to-cloud discharge. Thus, sheet lightning is no unique form of lightning but only one manifestation of ordinary lightning types in the presence of obscuring clouds. Compare heat lightning.
Industry:Weather
An instrument that measures, electronically, the direction of arrival, intensity, and rate of occurrence of atmospherics; a type of radio direction finder, it is most commonly used to detect and locate cloud-to-ground lightning discharges from distant thunderstorms. In its simplest form the instrument consists of two orthogonally crossed antennas that measure the electromagnetic field changes produced by a lightning discharge and determine the direction from which the changes arrived. Negative and positive polarity cloud-to-ground discharges can be distinguished. Cloud-to-cloud discharges can be distinguished based on characteristics of the received signal, and the geometry of nearby discharge channels may be determined. See'' also'' narrow- sector recorder, lightning detection network.
Industry:Weather
An instrument that measures, electronically, the direction of arrival, intensity, and rate of occurrence of atmospherics; a type of radio direction finder, it is most commonly used to detect and locate cloud-to-ground lightning discharges from distant thunderstorms. In its simplest form the instrument consists of two orthogonally crossed antennas that measure the electromagnetic field changes produced by a lightning discharge and determine the direction from which the changes arrived. Negative and positive polarity cloud-to-ground discharges can be distinguished. Cloud-to-cloud discharges can be distinguished based on characteristics of the received signal, and the geometry of nearby discharge channels may be determined. See'' also'' narrow- sector recorder, lightning detection network.
Industry:Weather
A cloud modeling term for the growth of large drizzle drops by collision and coalescence with smaller drizzle drops. This process is identified as being responsible for the rapid increase in the mode size of the precipitation liquid water spectrum. Self-collection, autoconversion, and accretion have been identified as the primary governors of the collision–coalescence process.
Industry:Weather
An atmospheric ion of the type that has the greatest mobility and hence, collectively, is the principal agent of atmospheric conduction. The exact physical nature of the small ion has never been fully clarified, but much evidence indicates that each is a singly charged atmospheric molecule (or, rarely, an atom) about which a few other neutral molecules are held by the electrical attraction of the central ionized molecule. Estimates of the number of satellite molecules are as high as twelve. When freshly formed by any of several atmospheric ionization processes, small ions are probably singly charged molecules, but after a number of collisions with neutral molecules they acquire (actually, in a fraction of a second) their cluster of satellites. Even with these satellites clustering about the central charged molecules, the ion mobility of the resulting complex is of the order of 10<sup>4</sup> times greater than that of large ions. Negative small ions exhibit slightly greater mobilities than positive small ions, 1. 9×10<sup>−4</sup> m s<sup>−1</sup> per volt cm<sup>−1</sup> being typical of negative, and 1. 4×10<sup>−4</sup> m s<sup>−1</sup> per volt m<sup>−1</sup> being typical of positive small ions in dry air at sea level. Small ions may disappear either by direct recombination with oppositely charged small ions or by combination with neutral Aitken nuclei to form new large ions, or by combination with large ions of opposite sign. The concentration of small ions near sea level is typically about 5×10<sup>−4</sup> of each sign per m<sup>3</sup>, both over the oceans and over land. This concentration increases with altitude, and at 18 km it is about 10<sup>−3</sup> per m<sup>3</sup>.
Industry:Weather
A cloud modeling term for the growth of large drizzle drops by collision and coalescence with smaller drizzle drops. This process is identified as being responsible for the rapid increase in the mode size of the precipitation liquid water spectrum. Self-collection, autoconversion, and accretion have been identified as the primary governors of the collision–coalescence process.
Industry:Weather
A moist-adiabatic process in which the liquid water that condenses is assumed to be removed as soon as it is formed, by idealized instantaneous precipitation. The pseudoadiabatic process is only defined for expansion, since a parcel that is compressed after such expansion will follow the dry-adiabatic lapse rate. A process similar to pseudoadiabatic descent can occur, however, if drizzle is evaporated into a relatively slow downdraft.
Industry:Weather
A moist-adiabatic process in which the liquid water that condenses is assumed to be removed as soon as it is formed, by idealized instantaneous precipitation. The pseudoadiabatic process is only defined for expansion, since a parcel that is compressed after such expansion will follow the dry-adiabatic lapse rate. A process similar to pseudoadiabatic descent can occur, however, if drizzle is evaporated into a relatively slow downdraft.
Industry:Weather
A frozen layer of ground, at the base of the active layer, that may persist for one or several years. The term is Russian meaning “survives over the summer. ” Pereletok may easily be mistaken for permafrost.
Industry:Weather
