APPENDIX II 



GLOSSARY 



ABSOLUTE INSTABILITY, The state of a 

 column of air in the atmosphere when it has 

 a super adiabatic lapse rate of temperature. An 

 air parcel displaced vertically would be ac- 

 celerated in the direction of the displacement. 



ABSOLUTE STABILITY. The state of a column 

 of air in the atmosphere when its lapse rate 

 of temperature is less than the saturation adia- 

 batic lapse rate. The parcel will be more dense 

 than its environment and tend to sink back to 

 its level of origin. 



ABSORPTION. The process in which incident 

 radiant energy is retained by a substance. 



ADVECTION. The process of transporting 

 an atmospheric property solely by the mass 

 motion (velocity field) of the atmosphere. 



ADVECTION FOG. A type of fog caused 

 by the advection of moist air over a cold sur- 

 face, and the consequent cooling of that air to 

 below its dew point. 



AIR MASS. A widespread body of air that 

 is approximately homogeneous in its horizontal 

 extent, with reference to temperature and mois- 

 ture. 



ALBEDO. The ratio of the amount of elec- 

 tromagnetic radiation reflected by a body to the 

 amount incident upon it. 



ALTIMETER SETTING, The pressure value 

 to which an aircraft altimeter scale is set so 

 it will indicate the altitude above MSL of an 

 aircraft on the ground at the location for which 

 the value was determined. 



ANABATIC WIND. An upslope wind; usually 

 applied only when the wind is blowing up a hill 

 or mountain as the result of surface heating. 



ANTICYCLOGENESIS. The strengthening or 

 development of an anticyclonic circulation in the 

 atmosphere. 



ANTICYCLOLYSIS. The weakening of 

 anticyclonic circulation in the atmosphere. 



an 



ANTICYCLONE. A closed anticyclonic circu- 

 lation in the atmosphere. Used interchangeably 

 with high. 



ANTICYCLONIC. A clockwise rotation in the 

 Northern Hemisphere and counterclockwise in 

 the Southern Hemisphere. 



AUTOCONVECTIVE LAPSE RATE. The en- 

 vironmental lapse rate of temperature in an 

 atmosphere in which the density is constant 

 with height. 



BACKING. A change in wind direction in a 

 counterclockwise sense in the Northern Hemi- 

 sphere and clockwise in the Southern Hemisphere. 



BALLISTIC DENSITY. A representation of 

 the atmospheric density actually encountered by 

 a projectile in flight, expressed as a percentage 

 of the density according to the standard artillery 

 atmosphere. 



BATHYTHERMOGRAPH. A device for obtain- 

 ing a record of temperature against depth in 

 the ocean. 



BLACK BODY. A hypothetical body which 

 absorbs all of the electromagnetic radiation 

 striking it; one which neither reflects nor trans- 

 mits an if the incident radiation. 



BLOCKING HIGH. Any high or anticyclone that 

 remains nearly stationary or moves slowly west- 

 ward so it effectively blocks the movement of 

 migratory cyclones across its latitudes. 



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