- Industry: 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, ...
The region of the diffraction pattern close to a scattering angle of 0°. As particles become large compared with the wavelength of incident radiation, the diffraction peak becomes larger and tends to dominate the entire diffraction pattern, giving rise to most of the diffraction pattern effects associated with geometric optics.
Industry:Weather
An interference pattern of scattered light centered on a scattering angle of 0°. This pattern is due to the various phase relationships among the different paths that the electromagnetic radiation takes in going around, or through, a scattering particle, leading to constructive or destructive interference. In general, the larger the cross section of the particle, or the shorter the wavelength of the radiation, the narrower the angular spread of the diffraction pattern.
Industry:Weather
Vertical derivative (or difference) of thermal advection.
Industry:Weather
The temperature to which a given air parcel must be cooled at constant pressure and constant water vapor content in order for saturation to occur. When this temperature is below 0°C, it is sometimes called the frost point. The dewpoint may alternatively be defined as the temperature at which the saturation vapor pressure of the parcel is equal to the actual vapor pressure of the contained water vapor. Isobaric heating or cooling of an air parcel does not alter the value of that parcel's dewpoint, as long as no vapor is added or removed. Therefore, the dewpoint is a conservative property of air with respect to such processes. However, the dewpoint is nonconservative with respect to vertical adiabatic motions of air in the atmosphere. The dewpoint of ascending moist air decreases at a rate only about one-fifth as great as the dry-adiabatic lapse rate. The dewpoint can be measured directly by several kinds of dewpoint hygrometers or it can be deduced indirectly from psychrometers or devices that measure the water vapor density or mixing ratio. See dewpoint formula.
Industry:Weather
The process by which the direction of radiation is changed so that it spreads into the geometric shadow zone of an opaque or refractive object that lies in a radiation field. Diffraction is an optical “edge effect,” differing only in degree from scattering. Diffraction becomes more evident when dealing with particles similar to, or larger than, the wavelength of the radiation. In meteorological optics, important diffraction phenomena include the aureole, Bishop's ring, corona, iridescent clouds, etc. The principle of diffraction may also be applied to the propagation of water surface waves, as into the sheltered region formed by a barrier.
Industry:Weather
A pattern of thickness lines that is concave toward low thickness and in which the thickness lines separate in the direction of the thermal wind.
Industry:Weather
A pattern of thickness lines that is concave toward high thickness and in which the thickness lines separate in the direction of the thermal wind.
Industry:Weather
The rate of change of water content with soil water pressure. Its value will depend on whether volumetric or gravimetric water content is used and how pressure is expressed.
Industry:Weather
The ratio of radar reflectivity measured by means of two signals that differ in one attribute, for example, polarization or wavelength. As applied to polarimetric radar observations, the differential reflectivity is the ratio of the reflectivity observed with transmitted and received signals of horizontal polarization to that observed with signals of vertical polarization. It is commonly represented by the symbol ZDR. The ratio of radar reflectivity measured with two signals of different wavelength is more commonly described as the dual-wavelength ratio.
Industry:Weather
The difference in the phase shift, due to propagation, experienced by two signals that differ in one attribute, for example, polarization or wavelength. As applied to polarimetric radar observations, the differential phase shift is defined relative to the axes of the propagation medium for which the phase shift is minimum and maximum. These axes are described as the principal axes of the medium.
Industry:Weather
