- 行业: Weather
- Number of terms: 60695
- Number of blossaries: 0
- Company Profile:
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 course, route, or track along a great circle over the earth's surface. The great-circle course is the least distance between two points on a sphere. The angle between the great circle and true north changes along the course except along a meridian or the equator. See rhumb-line course, grid navigation.
Industry:Weather
A cross-mountain wind that causes clouds to form on the crests of mountains in Italy.
Industry:Weather
A classification of fog intensity based on its effectiveness in decreasing horizontal visibility. Such practice is not current in U. S. Weather observing procedures.
Industry:Weather
A class of rain gauge in which the level of the collected rainwater is measured by the position of a float resting on the surface of the water. This instrument is frequently used as a recording rain gauge by connecting the float through a linkage to a pen that records on a clock-driven chart.
Industry:Weather
A circular zone centered about the direct path between a transmitter and a receiver (or between radar antenna and target), so defined that the distance along a path from transmitter to receiver through a point within the zone has a path length equal to some value between (L + nλ/2) and (L + (n + 1)λ/2), where L is the length of the direct path, λ is the wavelength, and n is a positive integer or zero. The first Fresnel zone is the zone defined by n = 0 and containing the minimum path length. Fresnel zones are a useful concept for analyzing the interference between the direct signal on a propagation path and signals reflected by objects that are displaced from the direct path. Thus, for a given path, reflected radio energy arriving at the receiver from any point will have a phase determined by the particular Fresnel zone in which the point is located. Reflected signals from zones defined by even values of n will interfere constructively with the direct signal; those from zones defined by odd values of n will interfere destructively.
Industry:Weather
A chemical species that possesses an unpaired electron. These compounds, such as chlorine monoxide (ClO), hydroxyl radical (OH), and nitric oxide (NO), are characterized by a high chemical reactivity. Free radicals are often generated in the atmosphere from the photodissociation of more stable species. Their subsequent chemistry is central to such environmental issues as stratospheric ozone depletion and tropospheric oxidant production.
Industry:Weather
1. An air layer next to the ground surface with its vertical extent controlled by atmospheric turbulence and surface roughness. See surface boundary layer. 2. The top layer of soil that interacts with the atmosphere.
Industry:Weather
1. An area of firn that is not part of a glacier. 2. Same as accumulation area.
Industry:Weather
1. An equation that relates the vertical turbulent flux of a quantity to the shape or slope of the vertical profile of the mean value of that quantity, usually applied in the surface layer of the atmospheric boundary layer. For example, in the surface layer the wind speed increases approximately logarithmically with height, at a rate that depends on the friction velocity u* and the Obukhov length L. Because both these last two variables depend on surface fluxes, it is possible to find these fluxes from measurements of the mean wind profile, a technique that can be easier and less costly than measuring the fluxes directly. 2. Same as universal functions.
Industry:Weather
1. Any material that, by absorption or reflection, selectively modifies the radiation transmitted through an optical system. 2. To remove a certain component or components of radiation, usually by means of a filter, although other devices may be used. 3. A mathematical tool used to remove information within certain frequency (or wavelength) limits from a time (or space) series of data. Filters are commonly used to remove high (low) frequency oscillations from a dataset when oscillations of low (high) frequency are of interest.
Industry:Weather
