Pacific anticyclone — See Pacific high. 



Pacific high — (or Pacific anticyclone ) . The near- 

 ly permanent subtropical high of the North 

 Pacific Ocean, centered in the mean, at 30° to 

 40°N and 140° to 150°W. 



On mean charts of sea level pressure, this 

 high is a principal center of action. (5) 



Pacific Ocean — The ocean area bounded on the 

 east by the western limits of the coastal waters 

 of southwest Alaska and British Columbia, the 

 southern limits of the Gulf of California, and 

 from the Atlantic Ocean by the meridian of 

 Cape Horn to Antarctica; on the north by the 

 southern limits of Bering Strait and the Gulf 

 of Alaska ; on the west by the easternly limits 

 of the Sea of Okliotsk, Japan Sea, Philippine 

 Sea, the East Indian Arclupelago from Luzon 

 Island to New Guinea, Bismarck Sea, Solomon 

 Sea, Coral Sea, Tasman Sea, and from the In- 

 dian Ocean by a line from Southeast Cape (the 

 southern point of Tasmania) down the meridian 

 to the Antarctic Continent. The Equator sepa- 

 rates the Pacific Ocean into the North and South 

 Pacific Oceans. 



The limits of the Pacific Ocean exclude the 

 seas lying within it. 



pack — A short term for ice pack or pack ice. 

 (65) 



packed ice — See close ice. 



pack ice — (also called drift ice, ice pack^ pach). 

 1. The term used to denote any area of sea ice 

 other than fast ice, no matter what form it takes 

 or how disposed. (74) 



The WMO Code defines very open pack ice 

 as ice of 1- to 3-tenths concentration, open pack 

 ice as 4- to 6-tenths concentration, close pack 

 ice as ice of 7- to 9-tenths concentration, and 

 very close pack ice as ice of 10-tenths concen- 

 tration. 



2. A large area of floating ice which has been 

 driven together. The concentration can gen- 

 erally vary between 1- and 10-tenths. Other 

 terms that can be applied to pack ice include : 

 broken, loose, consolidated, and unbroken. The 

 terms pack ice and ice pack have been used in- 

 discriminately for both the sea area containing 

 floating ice and the ice itself. 



packing — The spacing or density pattern of the 

 mineral grains in a rock or sediment. (2) 



painter — (also called Callao painter, El Pintw). 

 A fog frequently experienced on the coast of 

 Peru. The brownish deposit which it often 



leaves upon exposed surfaces is sometimes called 

 Peruvian paint. (5) 



pair production — Aji absorption process for X- 

 and gamma radiation in which the incident pho- 

 ton is annihilated in the vicinity of the nucleus 

 of the absorbing atom with subsequent produc- 

 tion of an electron and positron pair. This reac- 

 tion only occurs for incident photon energies ex- 

 ceeding 1.02 million-electron-volts. (70) 



paleocrystic ice — Old sea ice, generally consid- 

 ered to be at least ten years old ; it is nearly al- 

 ways a form of pressure ice, and often is found 

 in floebergs and in the pack ice of the central 

 Arctic Ocean. (5) 



paleomagnetism — Remanent magnetism pro- 

 duced by the earth's field when a material was 

 initially formed. 



Palolo worm — A species {Eimice viridis) of poly- 

 chaete worms which spawns in vast, freeswim- 

 ming swarms over the reefs of the Samoan and 

 Fiji Islands during the last quarter of the moon 

 at the lowest tides during October and 

 November. 



pan — An individual piece of pancake ice. (68) 



pancake ice — (also called lilly-pad ice, plate ice). 

 1. Pieces of newly-formed ice, usually approxi- 

 mately circular, about 30 centimeters (12 inches) 

 to 3 meters ( 10 feet) across, and with raised rims 

 caused by the striking together of the pieces as 

 a result of wind and swell. (74) 



2. One or more pieces of newly-formed flloat- 

 ing ice, usually between 1 and 6 feet in diameter, 

 with raised rims and circular outline caused by 

 rotation and collision with other ice fragments. 

 (59) 



Paper Nautilus — See nautilus. 



parachute drogue — See drogue. 



parallax — 1. A tide term referring to the angle 

 at the center of a celestial body between a line 

 to the center of the earth and a line tangent to 

 the earth's surface ; the ratio of the mean radius 

 of the earth to the distance of the tide-producing 

 body. The term is usually applied to inequali- 

 ties in the tide which result from the continually 

 changing distance of the principal tide-produc- 

 ing body, the moon. See parallax inequality. 

 (50) 



2. The change in apparent position of a nearby 

 object compared with more remote reference 

 objects wlien the nearby object is viewed from 

 two different points in space. 



119 



