- 行业: Weather
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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, ...
1. The nature of a region with respect to its elevated terrain. 2. That branch of geomorphology that deals with the disposition and character of hills and mountains.
Industry:Weather
Commonly known as OI, this procedure provides an estimate of the state of the atmosphere by a weighted least squares fit to observations and a background field, usually provided by a NWP model forecast. The weights are the inverse of the error covariance matrices for the observations and the background field. The word “optimum” is misleading, because in practice it is difficult to define the error covariances accurately. A more appropriate term is “statistical interpolation. ”
Industry:Weather
Amount of annual withdrawal from an aquifer or reservoir that best meets a set of economic, environmental, and/or social objectives, subject to a set of prescribed constraints.
Industry:Weather
A perturbation that is intended to produce the largest (optimal) change to a forecast measure ''J''. For example, if ''J'' is a measure of forecast error, an optimal perturbation δ''x'' could represent a change to the forecast's initial conditions designed to minimize forecast error, given a constraint that δ''x'' has magnitude comparable to the typical analysis errors of operational forecast models. See adjoint sensitivity.
Industry:Weather
1. The (dimensionless) line integral of the absorption coefficient, or of the scattering coefficient, or of the sum of the two, along any path in a scattering and absorbing medium. More often than not, the qualifiers “absorption,” “scattering,” and “total” are omitted (context sometimes being sufficient to determine which is meant). Optical thickness also depends on the wavelength of the radiation of interest. In a uniform medium, optical thickness has a simple physical interpretation as the length of a path in units of mean free path. Optical thickness and optical depth are used more or less synonymously; if there is a distinction between them it is that optical thickness is applied to an entire path through a medium. Normal optical thickness is optical thickness along a vertical path. Compare optical pathlength. 2. The degree to which a cloud modifies the light passing through it. Optical thickness depends on the physical constitution (crystals, drops, droplets), and the form; the overall effect depends on the scatter parameter and the phase function for the particles as well as their concentration and the vertical extent of the cloud.
Industry:Weather
A type of optical particle probe that measures the forward scattering caused by each particle or ensemble of particles intercepting a laser beam. The scattering is converted to an equivalent size via calibration and scattering theory for spheres. Examples are the passive cavity aerosol spectrometer probe, normally for sizing 0. 1–3. 0-μm diameter aerosols, the forward scattering spectrometer probe, normally for sizing either 0. 3– 20-μm or 0. 5–47-μm aerosols and cloud droplets, and the optical cloud drop spectrometer, normally for sizing 2–200-μm cloud droplets.
Industry:Weather
A gauge that measures the scintillation in an optical beam produced by raindrops falling between a light source and an optical receiver. By measuring the energy in selected frequency bands of the scintillation spectrum and comparing their ratios, the occurrence of precipitation, type of precipitation, and intensity of precipitation can be estimated.
Industry:Weather
(Sometimes called optical path or optical length. ) The line integral of the refractive index (real part) along a ray connecting two points in an optically homogeneous medium. Because refractive index depends on frequency, so does optical pathlength. Although optical pathlength may be shortened to optical path, there is a difference between a path and its length. Compare optical thickness.
Industry:Weather
1. Same as line of sight. 2. The integral of the volume extinction coefficient over the path traveled by monochromatic radiation.
Industry:Weather
An optical particle probe that records the size and shape of the shadow of each particle that intercepts and attenuates the illumination by a laser beam. Of these, shadowing probes differentiate particle shadows from the light of the unobstructed beam with linear arrays of optically activated diodes; for example, the one-dimensional cloud probe normally for sizing 10-μm to either 300- or 600-μm cloud hydrometeors, the two-dimensional cloud probe normally for sizing and imaging 25–800-μm cloud hydrometeors, and the two-dimensional precipitation probe normally for sizing and imaging 200-μm to 6. 4-mm precipitation hydrometeors. The electronics record either the maximum one-dimensional width of the shadow or two dimensions and shape of the shadow, to estimate particle size and type (raindrop, crystal growth habit, etc. ). Another type, the cloud particle imager, illuminates each particle with a pulsed laser and records size, shape, and detailed structure of each hydrometeor with a high-resolution solid-state digital imaging camera, normally to size 5-μm–2. 3-mm hydrometeors.
Industry:Weather
