designed to measure the speed (or force) of the 

 wind. These instruments may be classified accord- 

 ing to the means of transduction employed: those 

 used in meteorology include the rotation anemometer, 

 pressure plate anemometer, pressure-tube anemometer, 

 bridled-cup anemometer, contact anemometer, cooling- 

 power anemometer, and sonic anemometer. (24) 



ANEROID BAROGRAPH . An ANEROID BAROMETER arranged 

 so that the deflection of the aneroid capsule ac- 

 tuates a pen which graphs a record on a rotating 

 drum. The magnification of the deflection of the 

 capsule may be adjusted so that records of small 

 fluctuations in pressure may be obtained. The 

 aneroid barograph is subject to the uncertainties 

 of the aneroid, barometer, and therefore must be 

 calibrated periodically. (24) 



ANEROID BAROMETER . An instrument for measuring 

 atmospheric pressure. It is constructed on the 

 following principles: an aneroid capsule (a thin 

 corrugated hollow disk) is partially evacuated of 

 gas, and is restrained from collapsing by an exter- 

 nal or internal spring. The deflection of the 

 spring will be nearly proportional to the differ- 

 ence between the Internal and external pressures. 

 Magnification of the spring deflection is obtained 

 both by connecting capsules in series and by me- 

 chanical linkages . 



The aneroid barometer is temperature compen- 

 sated at a given pressure level by adjustment of 

 the residual gas in the aneroid or by a bimetallic 

 link arrangement. The Instrument is subject to 

 uncertainties due to variations in the elastic 

 properties of the spring and capsules, and due to 

 wear In the mechanical linkages . (24) 



ANGEL . A radar echo caused by a physical phenom- 

 enon not discernible to the eye. Angels are 

 usually coherent echoes and sometimes of great sig- 

 nal strength (up to 40 db above the noise level) . 

 They have been ascribed to Insects flying through 

 the radar beam, but have also been observed under 

 atmospheric conditions which Indicate there must 

 be other causes. Studies Indicate that a fair por- 

 tion of them are caused by strong temperature and/ 

 or moisture gradients such as might be found near 

 the boundaries of bubbles of especially warm or 

 moist air. They frequently occur in shallow layers 

 at or near temperature inversions within the lowest 

 few thousand feet of the atmosphere. (24) 



ANGLE OF REPOSE . The greatest angle to the hori- 

 zontal assumed by any unsupported granular, semi- 

 solid, or semifluid material. Also called natural 

 slope. (27) 



ANGLE OF ROLL . The angle between the lateral axis 

 of a craft and the horizontal. It is considered 

 positive of the port side is higher than the star- 

 board side, but may be designated starboard or port 

 depending upon which side is lower. Also called 

 angle of bank, roll angle. (17) 



ANGLE OF YAW . 1. 

 ment of the longl 

 neutral position, 

 right or left ace 

 placement of the 

 2. 

 direction of the 

 the longitudinal 

 It is considered 

 to the right. 



Also called 



The horizontal angular dlsplace- 

 tudinal axis of a vessel from its 



during a yaw. It is designated 

 ording to the direction of dis- 

 bow. 



The angle between a line in the 

 relative wind and a plane through 

 and vertical axes of an aircraft, 

 positive if the nose is displaced 



yaw angle. (17) 



ANGULAR SPREADING . The lateral extension of ocean 

 waves as they move out of the generating area as 

 swell. (24) 



ANGULAR-SPREADING FACTOR . In ocean wave forecast- 

 ing, the ratio of the actual wave energy present 

 at a point to that which would have been present 

 in the absence of ANGULAR SPREADING. (24) 



ANIP. Army-Navy Instrumentation Program. 



ANODE . The less noble electrode of an electrolytic 

 cell at which corrosion occurs. The corrosion 

 process involves the change of metal atoms into 

 ions with a liberation of electrons that migrate 

 through the metal to the cathode of the cell. 

 (35) 



ANOMALOUS DISPERSIVE . Waves having crests which 

 are short compared to the wavelength. 



ANOMALOUS PROPAGATION . In sonar, pronounced and 

 rapid variations in echo strength caused by large 

 and rapid local fluctuations in propagation con- 

 ditions. (8) 



ANOXIA . (Also called HYPOXIA) . Oxygen deficiency 

 in the blood cells or tissues of the body in such 

 degree as to cause psychological and physiological 

 disturbances. Anoxia may result from a scarcity 

 of oxygen in the air being breathed or from an 

 inability of the body tissues to absorb oxygen 

 under conditions of low ambient pressure. 



Anoxia can occur if large amounts of nitrogen 

 are present in the rebreathlng bags of closed or 

 semi-closed circuit rebreathlng apparatus and the 

 oxygen supply falls or becomes exhausted. The 

 onset of anoxia is frequently accompanied by a 

 feeling of elation and well being which is so 

 deceiving as to be difficult to recognize even by 

 experienced swimmers. The man usually loses con- 

 sciousness without warning. In pure oxygen re- 

 breathlng units , this can only occur through an 

 error in the diver's technique (poor nitrogen 

 elimination) and should be completely preventable 

 by training. Where nitrogen is intentionally used 

 in the breathing mixture, anoxia can result from 

 mechanical failure of the apparatus or exhaustion 

 of the gas supply. (37) 



ANTARCTIC CIRCLE . The line of latitude 66°32'S 

 (often taken as 66 1/2°S) . Along this line the 

 sun does not set on the day of the summer solstice, 

 about December 22nd, and does not rise on the day 

 of the winter solstice, about June 21st. (24) 



ANTARCTIC CIRCUMPOLAR CURRENT . The ocean current 

 with the largest volume transport (approximately 

 110 X 10^ m-^/sec), and the swiftest current; it 

 flows from west to east through all the oceans 

 around the Antarctic Continent. It is locally 

 deflected from its course, partly by the distri- 

 bution of land and sea and partly by the subma- 

 rine topography. Beside the bends that are as- 

 sociated with the bottom topography, the effects 

 of the distribution of land and sea and of the 

 currents in the adjacent oceans are also evident. 

 On its northern edge it is continuous with the 

 SOUTH ATLANTIC CURRENT, the SOUTH PACIFIC CURRENT 

 and the eastward-flowing extension of the AGULHAS 

 CURRENT in the Indian Ocean. 



A flow to the west near the Antarctic Con- 

 tinent is evident only in the Weddell Sea area, 

 where an extensive cyclonic motion occurs to the 

 south of the circumpolar current. (24) 



ANTARCTIC FRONT . The semi-permanent, semi-continu- 

 ous front between the antarctic air of the Antarc- 

 tic Continent and the Polar air of the southern 

 oceans ; generally comparable to the arctic front 

 of the Northern Hemisphere. (24) 



ANTARCTIC WHITEOUT . See ARCTIC WHITEOUT 



ANTILLES CURRENT . An ocean current, the northern 

 branch of the NORTH EQUATORIAL CURRENT flowing 

 along the northern side of the Great Antilles 

 carrying water that is Identical with that of the 

 Sargasso Sea. The Antilles current eventually 

 joins the FLORIDA CURRENT (after the latter emerges 

 from the Straits of Florida) to form the GULF 

 STREAM. (24) 



