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Section S S index 421-429 of 1376 terms
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simple vortex—See point vortex.
simple wave—The solution of a set of quasi-linear differential equations describing a fluid flow that possesses a family of straight-line characteristics. In such a fluid motion the dependent variables, or simple combinations thereof, are constant along the characteristics, and may be used as the basis of the integration of the equations by the method of characteristics. The simple waves of most interest to meteorology are the expansion wave and the compression wave. See simple harmonic wave.
sine galvanometer—A magnetometer of the electromagnetic type that is used to measure the horizontal intensity of the earth's magnetic field. The instrument serves as a national standard for measurement of this quantity.
single drift correction—In air navigation, a method of pressure-pattern flight utilizing a single value of drift-correction angle applied to an entire flight from point of origin to destination. The value is based upon a forecast of mean wind velocity en route. See multiple drift correction; compare aerologation, single-heading navigation.
single-grid-heading navigation—Same as aerologation.
single-heading navigation—1. A system of air navigation whereby a flight is accomplished using a single value of compass heading. The heading must be so determined that it compensates for the net effect of the wind en route. It should also be noted that a single-heading course rarely coincides with a great-circle course, except in grid navigation. Single-heading navigation is not necessarily economical in terms of least time, but its advantage lies in its simplicity. Compare single drift correction. 2. Same as aerologation.
single observer forecasting—Local weather forecasting that is based purely on observation of the weather elements for the same locality. The application of experience in synoptic meteorology, combined with physical reasoning, is capable of producing reasonably reliable local forecasts for a few hours ahead; in some situations reliability is possible for an appreciable time ahead. The observations chiefly used in such forecasting are those of pressure and pressure tendency, wind velocity at surface and higher levels, cloud, and temperature.
single-scatter albedo—The ratio of the scattering coefficient to the extinction coefficient. The single-scatter albedo affects radiative transfer in a scattering medium and is typically a function of wavelength. Throughout much of the visible spectrum, the single-scatter albedo of clouds and most atmospheric gases is very close to unity, and it typically varies considerably throughout the infrared spectrum.
single-scattering—A useful approximation to radiative transfer in which the radiation undergoes at most one scattering event. Single-scattering is most appropriate for scattering optical thicknesses less than about 0.1 when there is no absorption, but can be applied to thicker media as the single-scatter albedo is lowered.
single scattering—1. In a propagation medium consisting of a dispersion of scattering particles, the situation whereby the electromagnetic field in the vicinity of any particle is unaffected by scattering from the other particles. Then the total scattered field is just the sum of the fields scattered by the individual particles, each of which is acted on by the external field in isolation from the other particles. 2. The assumption that the total scattered field from a dispersion of scattering particles is the sum of the fields scattered by the individual particles. Whether single scattering is a good approximation depends on the characteristics of the particles, the wavelength of the radiation, and the way the scattered field is measured. It is more likely to be a good approximation for particles in dilute concentration that are small compared with the wavelength, and for experiments in which the beamwidth of the detector is narrow. The assumption of single scattering underlies the interpretation of most weather radar and wind profiler observations. For lidar, single scattering is said to occur when a transmitted photon experiences just one scattering event before returning to the receiver. Compare multiple scattering.
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