AGI . American Geological Institute. 



AGM . U. S. Navy designation for Missile Range 

 Instrumentation ships. 



AGMR . U. S. Navy designation for a Major Com- 

 munications Relay Ship. 



AGONIC LINE . See ISOGONIC LINE. 



AGOR . U. S, Navy designation for an Auxiliary 

 General Oceanographlc Research Ship. This class 

 of ship is 209 feet long with a 39 foot beam. 



AGR . U. S. Navy designation for a Radar Picket 

 Ship. 



AGS . U. S. Navy designation for an Auxiliary 

 General Survey Ship. These ships are about twice 

 the size of the AGOR ships. 



AGSC. U. S. Navy designation for an Auxiliary 

 General Survey Coastal Ship. 



AGSL. U. S. Navy designation for a Satellite 

 Launching Ship. 



AG(SS) . U. S. Navy designation for an Auxiliary 

 Submarine. 



AGU. American Geophysical Union. 



AH . U. S. Navy designation for a Hospital Ship. 



AGULHAS CURRENT . A generally southwestward- flow- 

 ing ocean current of the Indian Ocean; one of the 

 swiftest of ocean currents. 



Throughout the year, part of the SOUTH EQUA- 

 TORIAL CURRENT turns south along the east coast of 

 Africa and feeds the strong Agulhas current. To 

 the south of latitude 30 S. the Agulhas current is 

 a well-defined and narrow current that extends less 

 than 100 km from the coast. To the south of South 

 Africa the greatest volume of its waters bends 

 sharply to the south and then toward the east, thus 

 returning to the Indian Ocean by joining the flow 

 from South Africa toward Australia across the 

 southern part of that ocean. However, a small 

 portion of the Agulhas current water appears to 

 round the Cape of Good Hope from the Indian Ocean 

 and continues into the Atlantic Ocean. (24) 



Gases Per cent 



nitrogen (N2) - 78.084 



oxygen (O2) --------- 20.946 



argon (A) ------- 0.934 



carbon dioxide (CO2)" ----- 0.033 



neon (Ne) .----.- 0.0018 



helium (He) -- 0.000524 



methane (CH,) --------- 0.0002 



krypton (Kr) 0.000114 



hydrogen (H,) 0.00005 



nitrous oxide (NjO) ------ 0.00005 



xenon (Xe) - 0.0000087 



In addition to the above constituents there 

 are many variable constituents. Chief of these is 

 water vapor, which may vary from zero to volume 

 percentages close to four per cent. Ozone, sulfur 

 dioxide, ammonia, carbon monoxide, and other trace 

 gases occur in small and varying amounts. 



The sea-level composition of air is now known 

 to prevail up to twenty or twenty-five kilometers 

 without change, and only very slight diffusive 

 separation occurs even at heights as great as fifty 

 kilometers. (24) 



AIRBORNE RADIATION THERMOMETER (ART) . An instru- 

 ment carried aboard aircraft to measure ocean 

 surface temperatures. Actually, the radiation 

 thermometer compares the difference in temperature 

 between a self-contained standard temperature 

 reference and the ocean surface. 



AIRPLANE STRAND . See WIRE ROPE. 



AK . U. S. Navy designation for a Cargo Ship. 



AKA . U. S. Navy designation for an Attack Cargo 

 Ship. 



AKD . U. S. Navy designation for a Cargo Ship, Dock. 



AKL . U. S. Navy designation for a Light Cargo Ship. 



AKN . U. S. Navy designation for a Net Cargo Ship. 



AKS . U. S. Navy designation for a General Stores 

 Issue Ship. 



AK(SS) . U. S. Navy designation for a Cargo Sub- 

 marine . 



AKV . 0. S. Navy designation for a Cargo Ship and 

 Aircraft Ferry. 



AIBS . American Institute of Biological Sciences. 



AID . Agency for International Development. 

 (Formerly ICA) . 



AINA . Arctic Institute of North America. 



AIR. The mixture of gases comprising the earth's 

 ATMOSPHERE. Since the composition of the atmosphere 

 is slightly variable with respect to certain com- 

 ponents, the term "pure air" has no precise meaning, 

 but it is commonly used to imply freedom from non- 

 gaseous suspensoids (dust, hydrometeors) and also 

 freedom from such gaseous contaminants as industrial 

 effluents . 



By far the most important gas found in air, 

 from the meteorological viewpoint, is water vapor. 

 The term dry air denotes air from which all water 

 vapor has been removed. Pure dry air has a density 

 of 1.2923 gm/cm-^ at a pressure of 1013.25 mb and a 

 temperature of 0°C, a specific heat at constant 

 volume of 0.1707 cal/gm/°C; a specific heat at con- 

 stant pressure of 0.2396 cal/gm/°C- and its gas 

 constant (per gram) is 2.8704 x 10 erg/gra/°C. 



The per cent by volume of those gases found in 

 relatively constant amount in dry air is very near- 

 ly as follows: 



ALASKA CURRENT . An ocean current, the northward 

 flowing division of the ALEUTIAN CURRENT, it cir- 

 culates cyclonically around the Gulf of Alaska. 

 Part of the water passes between the Aleutian 

 Islands into the Bering Sea from which it emerges 

 as the OYASHIO, and part rejoins the Aleutian 

 current . 



It enters the Gulf of Alaska along the Ameri- 

 can west coast and, since it comes from the south, 

 it has the character of a warm current in spite of 

 the fact that it carries subarctic water. It 

 therefore exercises an influence on climatic con- 

 ditions similar, on a small scale, to that which 

 the NORTH ATLANTIC CURRENT and NORWEGIAN CURRENT 

 exercise on the climates of northwestern Europe. 

 (24) 



ALKALINITY . The quantity, when expressed as the 

 number of milli equivalents of hydrogen ions (mg- 

 atoms of H"*") , necessary to set free the ions of 

 weak acid in a volume of water which at 20° has a 

 volume of 1 L. 



ALBEDO . The ratio of the amount of electromagnetic 

 radiation reflected by a body to the amount inci- 

 dent upon it, commonly expressed as a percentage. 

 The albedo is to be distinguished from the reflec- 

 tivity, which refers to one specific wavelength 

 (monochromatic radiation) , (24) 



