- 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, ...
A scanning technique in airborne Doppler radar that makes use of both the aircraft motion and scanning to the side of the aircraft to survey the volume of atmosphere surrounding the flight track. Typically, the radar antenna is located in the tail of the airplane and rotates continuously about an axis aligned with the airplane. The pointing direction may be normal to the flight track or, as common for dual-beam airborne radars, may include pointing angles both forward and rearward of the direction normal to the flight track. The fore and aft directions provide measurements for dual-Doppler analysis that can be used to determine the three-dimensional velocity vector of the echoes.
Industry:Weather
A signal that is used to decide which subsets of data to include in an analysis. For example, an aircraft flying through a convective boundary layer will fly sometimes within thermal updrafts and sometimes between thermals. Positive vertical velocities that exceed some threshold could be used to indicate when a measurement is being made in a thermal. By averaging only those temperatures that were obtained within thermals as defined by the indicator function, an average temperature for the thermals can be found. This method of using indicator functions to select portions of a larger dataset is called conditional sampling.
Industry:Weather
A roughly cyclic variation in the zonal index. The average length of the index cycle is six weeks, varying from about three to eight weeks. It is most pronounced in the winter months.
Industry:Weather
A relatively high value of the zonal index which, in middle latitudes, indicates a relatively strong westerly component of wind flow and the characteristic weather features attending such motion. A synoptic circulation pattern of this type is commonly called a “high-index situation. ”
Industry:Weather
A relatively weak absorption band of ozone lying approximately between 310 and 340 nm. Absorption of direct solar radiation in this band led to the first positive identification of ozone in the atmosphere.
Industry:Weather
A relation between physical quantities of the form: x is proportional to 1/y2, where y is most often a distance, and x is often a force or flux. An example of the inverse square law is the decrease of radiative flux with distance from a point source, as is often used to approximate radiation reaching the earth from the sun.
Industry:Weather
A relatively bright region on the underside of clouds produced by the reflection of light by ice. This term is used in polar regions where it contributes to the sky map; ice blink is not as bright as snow blink, but is brighter than the reflection of light by land or water.
Industry:Weather
A radar echo with phase and amplitude that varies randomly and unpredictably from pulse to pulse. Such echoes are caused by incoherent scattering. Compare coherent echo.
Industry:Weather
A region in which the amount and seasonal variation of rainfall are of a given type. According to Köppen in his climatic classification, the main types of hyetal regions are 1) desert, with rainfall rare and irregular; 2) winter-dry, with main rainy season in summer, characteristic of a monsoon climate; 3) summer-dry, with rainy season in winter, such as a Mediterranean climate; 4) rain at all seasons, but not evenly distributed through the year; 5) rain on more than half the days in every month of the year. Minor types may be distinguished in which the season of rainfall maximum is either broken by a short dry season or is displaced toward spring or autumn. Compare humidity province.
Industry:Weather
A rain gauge that is placed under trees or in foliage to determine the rainfall in that location. By comparing this catch with that from a rain gauge set in the open, the amount of rainfall that has been intercepted by foliage is determined.
Industry:Weather
