- 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, ...
A method of searching decision trees in stages, beginning with a depth-first search. The search marks the last decision point and its alternatives. If one search path fails, the system backtracks to the most recent decision point, then follows an alternative branch. This permits searching as small a part of the tree as possible. Most instances of weather forecast expert systems are organized as decision trees, and use backtracking to improve their efficiency.
Industry:Weather
A method of generating balanced, fast-growing perturbations to a nonlinear model trajectory for a given finite perturbation amplitude. The technique consists of generating a control run of a nonlinear model for a short period of time (e.g., 6 h), then perturbing the atmospheric initial conditions and running the same model again for the same period of time (perturbed run). The difference between the two model runs at the final time is adjusted to the amplitude of the initial perturbation and is added to the new control initial condition. The method is then repeated. After a few days of iteration, the difference between the control and perturbed model runs represents a sample of fast-growing nonlinear perturbations. Multiple breeding cycles, started with different arbitrary initial perturbations, provide a broader sample of fast-growing perturbations. The technique can also be applied to a series of atmospheric analysis fields, where the control forecast always starts from the latest available analysis. See bred vectors.
Industry:Weather
A method of estimating horizontal divergence of air, using a triangular network of rawinsonde stations, devised by J. C. Bellamy in the late 1940s. At any one altitude, the wind measurements at the vertices of the rawinsonde triangle are linearly interpolated along the sides of the triangle to find the average wind component perpendicular to the side. When these normal wind components are multiplied by the length of the respective side, summed over all sides, and divided by the area of the triangle, the result is the average horizontal divergence within the triangle. Note that this method is sensitive to wind measurement errors and to the spacing between rawinsondes.
Industry:Weather
A meteorological variable averaged over the vertical depth of a layer, such as the convective mixed layer. For layers that are already relatively uniform with height, the bulk average is often used as an idealized value of that variable throughout the layer. For example, the potential temperature is often nearly constant with height in the mixed layer, so the vertical profile is often idealized to be exactly constant, with value equal to the bulk average potential temperature.
Industry:Weather
A measure of the quantity of oxygen used for biochemical oxidation of organic matter under specified conditions.
Industry:Weather
A measure of the mean thermodynamic stability in a layer beneath 700 mb. The Boyden index is given by I−Z−T−200, where I is the Boyden index, Z is the 1000–700- mb thickness in dam, and T is the 700-mb temperature in °C.
Industry:Weather
A measure of the concentration of power in a radar beam. The beamwidth in a given plane is the angle subtended at the antenna and containing the main lobe within which the intensity in the far field of the transmitted radiation is not less than a specified fraction of the intensity in the direction of the axis of the main lobe. Ordinarily, beamwidth is defined as the angle within which the intensity is not less than one- half the intensity on the beam axis (the 3-dB beamwidth). Sometimes beamwidth may refer to the linear extent of the beam in the cross-beam direction at some specified range. See antenna pattern.
Industry:Weather
A map designed for the presentation and analysis of data; it usually includes only the coordinates, geographical and major political outlines, and sometimes the larger lakes and rivers. Many modifications exist for specific uses throughout the geophysical sciences, such as the frequent inclusion of fixed reference points (or station positions). Mountains and contour lines are generally omitted, but high ground may be indicated by a single contour line and shading.
Industry:Weather
A map delineating the form of the bottom of a body of water, usually by means of depth contours (isobaths).
Industry:Weather
