ANGLE OP ROLL 



angle of roll — (also called angle of hanh, roll 

 angle). The angle between the lateral axis of 

 a craft and the horizontal. It is considered 

 positive if the port side is higher than the star- 

 board side, but may be designated starboard or 

 port depending upon which side is lower. (68) 



angle of yaw — (also called yaw angle). 1. The 

 horizontal angular displacement of the longi- 

 tudinal axis of a ship from its neutral position, 

 during a yaw. It is designated right or left 

 according to the direction of displacement of the 

 bow. 



2. The angle between a line in the direction 

 of the relative wind and a plane through the 

 longitudinal and vertical axes of an aircraft. 

 It is considered positive if the nose is displaced 

 to the right. 

 (68) 



angstrom — (abbreviated A, formerly A). A 

 unit of length used in the measurement of the 

 wavelength of light. X-rays, and other electro- 

 magnetic radiation and in the measurement of 

 molecular and atomic diameters. One angstrom 

 equals 10"' centimeter or 10"^ micron. (5) 



Angstrom compensation pyrheliometer — An 

 absolute instrument developed by K. Angstrom 

 for the measurement of direct solar radiation. 

 The radiation receiver station consists of two 

 identical manganic strips whose temperatures 

 are measured by attached thermocouples. One 

 of the strips is shaded, while the other is ex- 

 posed to sunlight. An electrical heating current 

 is passed through the shaded strip so as to raise 

 its temperature to that of the exposed strip. 

 The electric power required to accomplish this 

 is a measure of the solar radiation. (5) 



Angstrom pyrgeometer — An instrument de- 

 veloped by K. Angstrom for measuring the ef- 

 fective terrestrial radiation. It consists of four 

 manganic strips, of which two are blackened and 

 two are polished. The blackened strips are al- 

 lowed to radiate to the atmosphere while the 

 polished strips are shielded. The electrical 

 power required to equalize the temperature of 

 the four strips is taken as a measure of the out- 

 going radiation. (5) 



angular momentum — The moment of the linear 

 momentum of a particle about a point. If m 

 is the mass of the particle, V the velocity, and r 

 the position vector from the given point to the 

 particle, the angular momentum M about is 

 given by, 



M=r-'niV 



The angular momentum of a particle about an 

 axis is defined as that component, along the axis, 

 of the angailar momentum of the particle about 

 any point on the axis. 



The angular momentum of a continuous me- 

 dium is given by the integral of the product v V 

 over the mass of the medium. 



In meteorology, it is conventional to deal with 

 the angular momentum per unit volume, which 

 is given by the product r- p V, where p is the 

 density. (5) 



angular spreading — The lateral extension of 

 ocean waves as they move out of the generating 

 area as swell. (5) 



angular-spreading factor — In ocean wave fore- 

 casting, the ratio of the actual wave energy pres- 

 ent at a point to that which would have been 

 present in the absence of angular spreading. 



angular velocity — A representation of the rate of 

 rotation of a particle about the axis of rotation, 

 with magnitude equal to the time rate of angular 

 displacement of any point of the body. 



The angular velocity of the earth (in the ab- 

 solute coordinate system) is directed along the 

 earth's axis toward the pole star and is equal in 

 magnitude to 7.2921 X 10"^ radian per second. 



(5) 

 anion — A negatively charged ion. 



anisotropic — Not isotropic; that is, exhibiting 

 clifferent properties when tested along axes in 

 different directions. 



annelid — (or seg7nented loorm). One of a phy- 

 lum (Annelida or Annulata) of segmented 

 worms, with the majority of marine forms pos- 

 sessing a distinct head. Members of the group 

 are either free swimming, burrowing, or tube 

 building or may combine two of these modes of 

 living. Several tube-building species are no- 

 table fouling organisms. 



anniversary winds — A general term for local 

 winds or larger-scale wind systems (such as the 

 monsoon, etesians, etc.) that recur annually. 



(5) 



annual inequality — The seasonal or yearly varia- 

 tion in the water level or in the tidal current 

 speed ; more or less periodic, due chiefly to me- 

 teorological causes. (50) 



anomalistic tide cycle — The average period of 

 about 271/2 days, measured from perigee to peri- 

 gee, during which the moon completes one revo- 

 lution around the earth. 



anomalous — Not encompassed by rules governing 

 the majority of cases; distinguished from ab- 

 normal by implying a difference of kind rather 

 than a difference merely of degree. (5) 



anomalous field — See residual magnetic field. 



anomalous propagation — The propagation of en- 

 ergy (such as sound) when it arrives at a des- 

 tination via a path significantly different from 

 the normally expected path. (5) 



anomaly — 1. In oceanography, the difference be- 

 tween conditions actually observed at a serial 

 station and those that would have existed had 

 the water all been of a given arbitrary tempera- 

 ture and salinity. (5) 



2. A deviation from a norm. (37) 



3. In geophysics, the difference between the 

 theoretical or computed and actual value. (2) 



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