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Section S S index 371-379 of 1376 terms
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side-scanning sonar—A method of surveying the bottom of the ocean or other body of water to obtain detailed acoustic images, frequently used to locate debris, such as from aircraft accidents or sunken ships. The acoustic beam is directed perpendicularly to the direction of travel. The ship moves at a constant velocity, and each sonar ping insonifies a slightly different wedge of bottom. The apparent depth is actually the slant range from the ship to the target. The display is a map of slant range and distance along the track.
sideband—The frequency band, above or below the carrier frequency, that is produced by the process of modulation.
sidelobe—See lobe.
sidelooking radar—An airborne radar used for high-resolution ground mapping that employs a fixed antenna beam pointing out of the side of the aircraft. Narrow azimuth resolution is obtained with a long aperture mounted along the side of the aircraft or by use of synthetic aperture radar processing.
sidereal year—The time it takes the earth to complete one full orbit around the sun relative to the fixed stars.
siffanto—A southwest wind of the Adriatic Sea; it is often violent.
sigma-n—(Symbol σn, where n = 1, 2, etc.) The density (in kg m−3) that a parcel of water would have if moved adiabatically to n kilometers depth, less 1000 kg m−3; analogous to sigma-theta but with a deeper reference pressure.
sigma-STp—(Symbol σSTp.) The density (in kg m−3) that seawater of salinity S and temperature T would have at pressure p, less 1000 kg m−3. In symbols, where p is the atmospheric pressure relative to that at the sea surface. This definition includes the effects of compressibility in calculating the density but does not include the effects of adiabatic warming due to compression.
sigma-t,p—(Symbol σt,p.) Sigma-t, corrected to the hydrostatic pressure in situ.
sigma-t—(Symbol σt.) The density (in kg m−3) that seawater, of salinity S and temperature T, would have at sea level (i.e., at atmospheric pressure), less 1000 kg m−3. In symbols, where p = 0 is the atmospheric pressure relative to that at the sea surface.
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