- 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 stationary time series in which the joint probability distribution of any sequence of values, x(t1), x(t2),. . . , x(tn), is a multivariate normal distribution, or a stationary random process that is completely determined by its spectrum or autocorrelation function.
Industry:Weather
The upper portion of the exosphere, where the cone of escape equals or exceeds 180°. In this region the individual atoms have so little chance of collision that they essentially travel in free orbits, subject to the earth's gravitation, at speeds imparted by the last collision. See critical level of escape.
Industry:Weather
An unexpectedly occurring wave of great height (and also steepness), often found to occur where waves meet opposing currents, such as in the Agulhas Current off South Africa. Freak waves are known to cause serious damage to ships.
Industry:Weather
An unexpectedly occurring wave of great height (and also steepness), often found to occur where waves meet opposing currents, such as in the Agulhas Current off South Africa. Freak waves are known to cause serious damage to ships.
Industry:Weather
Subsurface water that occupies the zone of saturation; thus, only the water below the water table, as distinguished from interflow and soil moisture.
Industry:Weather
Subsurface water that occupies the zone of saturation; thus, only the water below the water table, as distinguished from interflow and soil moisture.
Industry:Weather
That part of an image focused on the fovea, a region of the retina near the optical axis of the eye. The fovea has a high density of the color-sensitive receptors known as cones, but it has no rods. Foveal vision permits much higher resolution than does parafoveal vision and is the normal mode of vision under daytime conditions. The vision in the fovea is exclusively photopic while in the parafoveal region it can be either photopic or scotopic. See dark adaptation.
Industry:Weather
That part of an image focused on the fovea, a region of the retina near the optical axis of the eye. The fovea has a high density of the color-sensitive receptors known as cones, but it has no rods. Foveal vision permits much higher resolution than does parafoveal vision and is the normal mode of vision under daytime conditions. The vision in the fovea is exclusively photopic while in the parafoveal region it can be either photopic or scotopic. See dark adaptation.
Industry:Weather
The highest frequency that can be measured using discretely sampled data. It is given by nf (rad s−1) = π/Δt, where nf is the Nyquist frequency and t is the time increment between observations. Stated another way, a minimum of two data points is needed to define a wave, hence the period of the smallest wave (i.e., the period corresponding to the Nyquist frequency) that can be measured is 2Δt. The word “folding” comes about because any frequencies that are higher than the Nyquist frequency in a continuous signal will be aliased or folded into lower frequencies when the signal is discretely sampled. To avoid this severe problem, the original signal must be filtered by analog or physical methods to remove all frequencies higher than the Nyquist frequency before the signal is sampled or digitized.
Industry:Weather
The highest frequency that can be measured using discretely sampled data. It is given by nf (rad s−1) = π/Δt, where nf is the Nyquist frequency and t is the time increment between observations. Stated another way, a minimum of two data points is needed to define a wave, hence the period of the smallest wave (i.e., the period corresponding to the Nyquist frequency) that can be measured is 2Δt. The word “folding” comes about because any frequencies that are higher than the Nyquist frequency in a continuous signal will be aliased or folded into lower frequencies when the signal is discretely sampled. To avoid this severe problem, the original signal must be filtered by analog or physical methods to remove all frequencies higher than the Nyquist frequency before the signal is sampled or digitized.
Industry:Weather
