SPECTRUM LEVEL 



spectrum level— The level of that part of a sig- 

 nal contained witli a band one cycle per second 

 wide, centered at the particular frequency. 

 Ordinarily this has significance only for a signal 

 having a continuous distribution of components 

 within tlie frequency range under consideration. 

 The phrase "spectrum level" cannot be used 

 alone, but must appear in combination with a 

 modifier, as, for example, pressure, velocity^ 

 voltage, etc. (3) 



spectrum stripper— The electronic accessory of a 

 multicliannel analyzer which performs spec- 

 trum stripping. 



spectrum stripping— The process of subtracting 

 known components of a gamma ray spectra to 

 reveal otherwise obscured spectral components. 



specular reflection — A mirrorlike or perfect re- 

 flection of sound rays from a smooth surface 

 or bottom. 



speed of advance — (abbreviated SOA) . The ex- 

 pected speed to be made good over the earth's 

 surface. 



spermatophyte — One of a division (Sperma- 

 tophyta) of plants, most of which possess true 

 stems, leaves, and roots, and all of which produce 

 seeds. Only a small group of seed plants are 

 marine. See seagrass. 



sperm whale — Largest of the toothed whales, or 

 odontocetes, attaining a length of about 60 feet. 

 It has a large blunt Iiead and a dispropor- 

 tionately small lower jaw bearing a series of 

 large conical teeth. A single species, Physeter 

 catodon, is recognized, occurring in all warm 

 seas. See toothed whale. 



spherical irradiance — Limit of the ratio of 

 radiant flux onto a spherical surface to the area 

 of the surface, as tlie radius of the sphere tends 

 toward zero with its center fixed. Unit of 

 measurement is watt per square meter (W/m-). 

 (8) 



spherical irradiance meter — A radiant flux 

 meter with spherical collecting surface of effec- 

 tive area A, every elemental area of which is a 

 cosine collector. If F is the radiant flux re- 

 corded by the meter, then the associated spheri- 

 cal irradiance is Eg = F/A . ( 8 ) 



spherical spreading — See spreading of sound. 



spherical wave — A wave ^yhose wave front sur- 

 faces are concentric spheres. Sucli waves prop- 

 agate from a point source. 



spicule — A minute needlelike or multiradiate cal- 

 careous or siliceous body in sponges, radio- 

 larians, primitive chitons, and echinoderms. 

 They frequently are identified in marine 

 sediment samples. 



Spilhaus-Miller sea sampler — A bathythermo- 

 graph with attached containers designed to col- 

 lect sea water samples at predetermined 

 depths. The sample bottles are triggered to 

 close at both ends by the pressure sensing ele- 

 ment of the batliythermograph. 



spilling breaker — See breaker. 



spiny lobster — One of a tribe (Palinura) of 

 crustaceans, individuals of which are prized 

 as food and are reported to make sounds of con- 

 siderable magnitude. 



spit — A small point of land or narrow shoal 

 projecting into a body of water from the shore. 

 (2) {See figure for recurved spit.) 



Spitsbergen Current — An ocean current flowing 

 northward and westward from a point south 

 of Spitsbergen, and gradually merging with the 

 East Greenland Current in the Greenland Sea. 

 The Spitsbergen Current is the continuation of 

 the northwestern branch of the Norway Cur- 

 rent. (68) 



splashnik — An expendable accelerometer tele- 

 metering buoy which provides surface wave 

 data. 



spoil banks — S ubmerged accumulations of 

 dumped material dredged from channels or har- 

 bors. The region where such material is 

 dumped is called spoil ground. 



spoil ground — An area where dredged material 

 is deposited. See dumping ground. (68) 



sponge — One of a phylum (Porifera) of solitary 

 or colonial, sessile animals of simple construc- 

 tion. Sponges are of many sizes and forms and 

 varied in color. 



spongin — A protein secretion, closely akin to silk, 

 whicli forms tlie skeleton of a fibrous sponge. 



spouting horn — Marine caves eroded in coastal 

 rocks which have openings to the air through 

 which water spouts or sprays as waves surge into 

 the cavern beneath. 



spray ice — Ice formed from blown spray, which 

 may occur along shore, on floating ice, on ships 

 or seaplanes. (59) 



spray ridge — One of a series of ice formations on 

 an ice foot, formed by the freezing of spray 

 blown from the waves by the wind. 



spreading anomaly — That part of the propaga- 

 tion anomaly which may be identified with the 

 geometry of the ray paths. (28) 



spreading of sound — The phenomenon whereby 

 transmitted sound intensity decreases in a con- 

 stant relation to distance from the sound source. 

 Three laws govern spreading, all relating sound 

 intensity to a ratio of distance from the sound 

 source. These spreading laws are : 

 l=\/r (cylindrical spreading) 

 I=l/r^ (inverse law or spherical spreading) 

 I=l/r^ (dipolar spreading), where /= sound 

 intensity and r= distance from sound 

 source. 



spring flowering — See spring maximum. 



spring high water — See mean high water 

 springs. 



spring low water — See mean low water springs. 



spring maximum — (or spring -fioioeTing) . The 

 abundance of marine phytoplankton (predomi- 

 nately diatoms) after a winter minimum. The 

 production of phytoplankton is generally the 



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