- 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, ...
The removal of components of a numerical solution of the hydrodynamical equations that correspond to time or space scales not of immediate interest. See Kalman–Bucy filter, meteorological noise.
Industry:Weather
Roughly, the amount of noise power in a signal. The noise level is a limit where simple power measurements start to have trouble measuring the signal.
Industry:Weather
A number by which the performance of a radio receiver can be specified. Essentially, the noise figure is the ratio of the noise generated by the actual receiver to the noise output of an “ideal” receiver with the same overall gain and bandwidth when the receivers are connected to a room temperature load. The noise power from a simple load is equal to ''kTB'', where ''k'' is Boltzmann's constant; ''T'' the absolute temperature of the load, for example, resistor; and ''B'' the measurement bandwidth. See also noise level, signal-to-noise ratio.
Industry:Weather
Thin silvery-blue cirrus-like clouds frequently seen during summer twilight conditions at high latitudes (above 50°) in both hemispheres. They are the highest visible clouds in the atmosphere, occurring in the upper mesosphere at heights of about 85 km, and are closely related to the polar mesospheric clouds seen in satellite observations at similar altitudes over the summer polar cap. Noctilucent clouds are now known to consist of tiny ice particles with dimensions of the order of tens of nanometers, growing in the extreme cold of the summer polar mesopause region. The condensation nuclei on which the particles grow are thought to be either smoke and dust particles of meteoric origin or large hydrated positive ions. Strong upwelling of air from below, associated with a pole-to-pole meridional circulation in the upper mesosphere, is responsible for both the extreme cold and the upward flux of water vapor. Although water-vapor mixing ratios are very low (less than 10 parts per million by volume) in the region, the temperatures are also low enough to produce a high degree of supersaturation at times. Anomalously strong radar echoes from the region, known as polar summer mesospheric echoes, are also associated with the clouds. Compare nacreous clouds, polar stratospheric clouds.
Industry:Weather
1. Any function, often of time but possibly of any variable, with a substantial lack of correlation between values at successive times. For example, the autocorrelation function of white noise is a sharp spike: Its value at any instant is correlated only with its value at that instant. 2. Any change in a signal that degrades its capability to transmit information (e.g., the audible static on AM radio resulting from lightning discharges). 3. See meteorological noise.
Industry:Weather
One of the two points of intersection of the orbit of a satellite with the plane of the equator of the earth. The ascending node of equatorial crossing refers to that point on the plane of the equator at which the satellite crosses from the Southern to Northern Hemisphere. The descending node of equatorial crossing denotes that point at which the satellite crosses the plane of the equator from the Northern to the Southern Hemisphere.
Industry:Weather
The time that elapses between successive passages of a satellite through successive ascending nodes.
Industry:Weather
The difference in degrees longitude between successive ascending nodes of a satellite in polar orbit. It is the amount of turning of the earth under the satellite, measured in degrees longitude, that takes place during one nodal period.
Industry:Weather
Small adjustments to the amplitudes and phases of harmonic tidal constituents to allow for modulations over an approximate 18. 61-year cycle, the period of a nodal tidal cycle.
Industry:Weather
