- 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 cgs unit of luminance (or photometric brightness) equal to one lumen, or 1/π candela per square centimeter. This luminance is produce by a blackbody source of luminous intensity 1 candela at a distance of 1 centimeter. The corresponding SI (or mks) unit is the apostilb, a unit 104 smaller produced by 1 candela at a distance of 1 m. The sun's disk at zenith at sea level under clear skies has a luminance of about 470 000 lambert, while that of a 60-watt, inside-frosted, tungsten-filament light bulb is about 38 lambert.
Industry:Weather
A captive balloon used to maintain meteorological equipment aloft at approximately a constant height. The kytoon is streamlined, and combines the aerodynamic properties of a balloon and a kite. See wiresonde.
Industry:Weather
1. Winds that, over a small area, differ from those that would be appropriate to the general large-scale pressure distribution, or that possess some other peculiarity. Often these winds have names unique to the area where they occur. Local winds may be classified into three main groups. The first includes diurnally varying airflows that are driven by local gradients of surface heat flux (e.g., near the shore of a sea or lake) or by diurnal heating or cooling of the ground surface in areas of sloping or mountainous terrain. These include land and sea breezes, mountain–valley circulations, and drainage and slope winds. The second group consists of winds produced by the interaction of a synoptic-scale flow with orography. These may be further subdivided into barrier jets, gap winds, downslope windstorms, and include such local phenomena as the tehuantepecer, Santa Ana, foehn, mistral, and bora. The third group includes those winds accompanying convective activity, more specifically individual thunderstorms or mesoscale convective systems. These are generally the surface manifestations of precipitation- cooled diverging outflow and in some locations are given special names due to the distinctive character of the weather associated with them (e.g., the haboob). 2. Local or colloquial names given to frequently occurring or particularly noteworthy winds (sometimes because of the bad weather associated with them), usually from a certain direction. Often these names reflect the direction from which the wind comes (e.g., sou'wester, nor'easter).
Industry:Weather
1. The vorticity of the earth about the local zenith. 2. Same as relative vorticity.
Industry:Weather
1. The solid portion of the earth, as compared to the atmosphere and the hydrosphere. 2. In plate tectonics, a layer of strength relative to the underlying asthenosphere for deformation at geologic rates. It includes the crust and part of the upper mantle and is of the order of 100 km in thickness. (Glossary of Geology 1997)
Industry:Weather
1. The removal of materials in solution from soil, rock, or waste. 2. Separation or dissolving out of soluble constituents from a porous medium by percolation of water.
Industry:Weather
1. That part of the difference between the output of an instrument and its input that is due to the failure of the instrument to respond instantaneously to variations of the input signal. It is a function of the instrument's time constant. See time lag. 2. A time displacement of a time series. See autocorrelation. 3. See delay.
Industry:Weather
1. Most widely used in mountain meteorology to denote a downslope flow driven by cooling at the slope surface during periods of light larger-scale winds; the nocturnal component of the along-slope wind systems. The surface cools a vertical column of the atmosphere starting at the slope surface and reaching perhaps 10–100 m deep. This column is colder than the column at equivalent levels over the valley or plain, resulting in a hydrostatic pressure excess over the slope relative to over the valley or plain. The horizontal pressure gradient, maximized at the slope surface, drives an acceleration directed away from the slope, or downslope. Although the pressure-gradient forcing is at its maximum at the slope, surface friction causes the peak in the katabatic wind speeds to occur above the surface, usually by a few meters to a few tens of meters. The depth of the downslope flow layer on simple slopes has been found to be 0. 05 times the vertical drop from the top of the slope. Surface-wind speeds in mountain–valley katabatic flows are often 3–4 m s−1, but on long slopes, they have been found to exceed 8 m s−1. Slopes occur on many scales, and consequently katabatic flows also occur on many scales. At local scales katabatic winds are a component of mountain– valley wind systems. At scales ranging from the slopes of individual hills and mountains to the slopes of mountain ranges and massifs, katabatic flows represent the nocturnal component of mountain–plains wind systems. Besides diurnal-cycle effects, surface cooling can also result from cold surfaces such as ice and snow cover. Katabatic flows over such surfaces have been studied as glacier winds in valleys and as large-scale slope flows in Antarctica and Greenland. The large- scale katabatic wind blowing down the ice dome of the Antarctic continent has sometimes reached 50 m s−1 on the periphery of the continent. The persistence of the surface forcing and the great extent of the slopes on these great landmasses means that the flows are subject to Coriolis deflection, and thus they are not pure katabatic flows. See downslope wind, gravity wind, drainage wind. 2. Occasionally used in a more general sense to describe cold air flowing down a slope or incline on any of a variety of scales, including phenomena such as the bora, in addition to thermally forced flows as described above. From its etymology, the term means simply “going down” or “descending,” and thus could refer to any descending flow; some authors have further generalized it to include downslope flows such as the foehn or chinook even though they do not represent a flow of cold air. This concept has given rise to the expression katafront, which indicates flow down a sloped cold-frontal surface.
Industry:Weather
1. In general, pertaining to the emission of visible radiation. 2. In photometry, a modifier used to denote that a given physical quantity, such as luminous emittance, is weighted according to the manner in which the response of the human eye varies with the wavelength of the light.
Industry:Weather
1. Cloud forms that arise from Kelvin–Helmholtz waves. 2. Vortical structures that result from the growth and nonlinear development of unstable waves in a shear flow. The billows get their name from the instability responsible for the growth of the unstable waves, Kelvin–Helmholtz instability.
Industry:Weather
