Greenland, flowing northward into Davis Strait as 

 the WEST GREENLAND CURRENT. 



The main discharge of the Arctic Ocean is via 

 the east Greenland current. (24) 



EASTROPIC . Eastern Tropical Pacific (Program). 

 EAU DE MER NORMALE . See NORMAL WATER. 



EBB CURRENT . The movement of a tidal current away 

 from shore or down a tidal stream. In the semi- 

 diurnal type of reversing current, the terms 

 greater ebb and lesser ebb are applied respectively 

 to the ebb currents of greater and lesser velocity 

 of each day. The terms maximum ebb and minimum 

 ebb are applied to maximum and minimum velocities 

 of a current running continuously ebb, the velocity 

 alternately increasing and decreasing without com- 

 ing to a slack or reversing. The expression maxi- 

 mum ebb is also applicable to any ebb current at 

 the time of greatest velocity. (14) 



EBB TIDE . A non-technical term referring to that 

 period of the tide between a high water and the 

 succeeding low water; falling tide. (11) 



EBULLISM . The formation of bubbles, with particu- 

 lar reference to water vapor bubbles in biological 

 fluids, caused by reduced ambient pressure. (31) 



ECHO . An echo is a wave that has been reflected 

 or otherwise returned with sufficient magnitude and 

 delay to be detected as a wave distinct from that 

 directly transmitted. (1) 



ECHO RANGING SONAR . (See ACTIVE SONAR) . 



ECHO REPEATER . Artificial target, used in sonar 

 calibration and training, which returns a synthetic 

 echo by receiving, amplifying, and retransmitting 

 an incident ping. (6) 



ECHO SOUNDER (SOUNDING MACHINE) . It is used for 

 measuring depth of water in open ocean areas. This 

 instrument consists of four parts; (1) A transmit- 

 ter which generates an electrical impulse which is 

 transmitted to (2) a transducer, which translates 

 the electrical impulse into a sonic impulse at the 

 same frequency either by means of the piezoelec- 

 tric effect of quartz or other crystals or the mag- 

 netostriction effect of a nickel alloy embedded in 

 a ceramic rod. The sonic impulse travels through 

 the water to the bottom, or any other reflecting 

 surface and an echo is returned to the transducer 

 where it is transformed again into an electrical 

 impulse and passed to (3) a regular radio frequency 

 receiver where the signal is detected, amplified, 

 and sent to (4) a recorder where the travel time 

 from the initial impulse to the return of the echo 

 is measured and displayed. Most American-built 

 instruments are calibrated for an assumed velocity 

 of sound in sea water of 4,800 feet per second. 

 The actual velocity varies with the temperature, 

 pressure, and salinity of the water in the column 

 being sounded. Echo sounding equipment can be 

 divided into three general classes of instruments; 

 general purpose, shallow water and deep water 

 instruments . (29) 



ECM. Electronic Counter-Measures . 



ECOLOGY. The relations of an organism to its 

 environment. (19) 



EC PP . Engineer's Council for Professional 

 Development . 



EDDY . 1. By analogy with a molecule, a "glob" of 

 fluid within the fluid mass that has a certain in- 

 tegrity and life history of its own; the activities 

 of the bulk fluid being the net result of the motion 

 of the eddies. 



The concept is applied with varying results to 

 phenomena ranging from the momentary spasms of the 

 wind to storms and anticyclones. 



2. Any circulation drawing its energy from a 

 flow of much larger scale, and brought about by 

 pressure irregularities as in the lee of a solid 

 obstacle. (24) 



3. A circular movement of water. Eddies 

 may be formed where currents pass obstructions or 

 between two adjacent currents flowing counter to 

 each other. (15) 



EDDY CONDUCTIVITY . The EXCHANGE COEFFICIENT for 

 Eddy Heat Conduction. (24) 



EDDY DIFFUSIVITY . The EXCHANGE COEFFICIENT for the 

 diffusion of a conservative property by EDDIES in 

 a turbulent flow. (24) 



EDDY FLUX . The rate of transport (or flux) of 

 fluid properties such as momentum, mass, heat, or 

 suspended matter by means of EDDIES in a turbulent 

 motion; the rate of turbulent exchange. (24) 



EDDY KINETIC ENERGY . The kinetic energy of that 

 component of fluid flow which represents a depar- 

 ture from the average kinetic energy of the fluid, 

 the mode of averaging depending on the particular 

 pr oblem . This eddy kinetic energy is represented 

 bypu'"^ where p is the density, u' is the EDDY 

 VELOCITY, and the superior bar denotes an average. 



In general circulation studies, for example, 

 the zonal average along a fixed latitude circle is 

 usually considered. As another example, in small- 

 scale turbulence studies it is frequently desirable 

 to consider the average with respect to time as a 

 fixed point in the fluid. (24) 



EDDY SPECTRUM . The distribution of the frequency 

 of EDDIES of various sizes or scales in a turbulent 

 flow, or the distribution of. kinetic energy among 

 eddies of various frequencies or sizes. (24) 



EDDY VELOCITY . The difference between the mean 

 velocity of fluid flow and the instantaneous 

 velocity at a point. For example, u' = u- u 

 where u' is the eddy velocity, u is instantaneous 

 velocity, and u is mean velocity. 



Over the same interval which defines the mean 

 velocity, the average value of the eddy velocity 

 is necessarily zero. (24) 



EDDY VISCOSITY . The turbulent transfer of momen- 

 tum by EDDIES giving rise to an internal fluid 

 friction, in a manner analogous to the action of 

 molecular viscosity in LAMINAR FLOW, but taking 

 place on a much larger scale. 



The value of the coefficient of eddy viscosity 

 (an exchange coefficient) is of the order of 10* 

 cm /sec, or one hundred thousand times the molecu- 

 lar kinematic viscosity. (24) 



EDGE WAVES . Widely spaced wave crests arranged at 

 right angles to the shore line. Such waves may be 

 excited by a wind shift associated with a passing 

 front . 



EEG . Electro-Encephalograph. 



EER . Explosive Echo Ranging. 



EERC. Explosive Echo Ranging Charge. 



EFFECTIVE ACOUSTIC CENTER . The effective acoustic 

 center of an acoustic generator is the point from 

 which the spherically divergent sound waves, ob- 

 servable at remote points, appear to diverge. (1) 



EFFECTIVE BACK RADIATION . The difference between 

 the "temperature radiation" from the sea surface 

 and the long -wave radiation from the atmosphere. 

 This effective radiation depends mainly upon the 



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