CLIMATE 



1431 



CLIMATE 



perature; but this is not the case because there 

 are so many modifying influences, altitude and 

 distance from the sea being the most im- 

 portant. 



Altitude. Altitude, or height above sea level, 

 affects temperature. The air grows thinner 

 and receives less heat from the earth in propor- 

 tion to the distance one rises, the temperature 

 falling one degree for about every 300 feet of 

 "M M M MM 



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CLIMATE AND TEMPERATURE CHART 

 The diagrams show the variations in tem- 

 perature in Chicago, 111., and Peoria, 111., on the 

 same days. The solid line represents Peoria, the 

 broken line, Chicago. The latter city is oh the 

 shore of a great body of water ; the former is 

 over a hundred miles inland. 



elevation. Thus, even in the tropics, a wide 

 range of temperature may be found in ascend- 

 ing a lofty mountain range one of the Andes 

 or Himalaya mountains, for instance. At the 

 foot one experiences the temperature of the 

 tropics; at 6,000 feet up, that of the temperate 

 zone ; at the summit, the eternal cold and snow 

 of polar regions. The great plateaus of the 

 tropics, which usually are at an altitude of 

 5,000 to 6,000 feet, have a cool climate. 



Distance from the Sea. The position of a 

 place or country with respect to the sea or to 

 other large bodies of water also determines 

 largely its climatic features. All places adja- 

 cent to the ocean or to the Great Lakes have a 

 much more equable climate than those situated 

 in the interior of a continent; the fact that the 

 water is cooler than the air in summer and 

 warmer in winter modifies the extremes of 

 temperature. Such places therefore are cooler 

 in summer and warmer in winter than locations 

 farther inland. 



Winds. An examination of a wind chart 

 (see WIND) shows that in equatorial regions 

 the great air currents forming the trade winds 

 have a northerly origin north of the equator 

 and a southerly origin south of it. They tend 

 therefore to modify the warmth of equatorial 

 regions. In each temperate zone the prevail- 

 ing winds originate in warm regions and blow 

 into the colder regions of higher latitudes. 

 When the moisture mingled with the air falls 



as rain an enormous amount of latent heat 

 is set free, warming the air still more. Thus 

 the west coast regions of the continents which 

 are in the temperate zones have much milder 

 winters than those of corresponding latitudes 

 on the east side of the continents. Because of 

 warm southwesterly winds, the winters of Sitka, 

 Alaska, are not colder than those of Philadel- 

 phia, nearly twenty degrees farther south. The 

 climate of England is mild; that of Eastern 

 Canada is hotter in summer and colder in 

 winter. 



The prevailing westerly winds also perform 

 another important office. They blow the sur- 

 face water of warm ocean currents into great 

 drifts, and the warm water keeps the harbors 

 and fiords in high latitudes free from ice during 

 long winters. Because of the wind-blown drift 

 of warm water, Hammerfest, a port within 

 the Arctic Circle, is open all the year ; on the 

 other hand, the fiords of Labrador, considerably 

 farther south, are ice-blocked more than half 

 the year. Cold ocean currents have the oppo- 

 site effect. The cold current coming down 

 from Baffin Bay hugs the Labrador coast, carry- 

 ing icebergs and cold fogs far into southerly 

 regions. . A cold current coming up from Ant- 

 arctic waters flows around the lower part of 

 South America and similarly affects its climate. 



Mountains and Rainfall. Mountain ranges 

 act as barriers and by preventing the free 

 passing of winds from one region to another 

 influence climate. The rainfall of localities 

 is greatly affected by these mountain barriers. 

 A wind passing over mountains leaves its 

 moisture on the windward side and becomes 

 a hot, dry wind on the opposite side. Thus 

 the Pacific coast has an excessive rainfall, 

 while some of the regions east of the mountains 

 are hot and arid and are called the Great 

 American Desert. The Sahara Desert in 

 Northern Africa likewise is the result of moun- 

 tain barriers, and the hot winds that blow from 

 it and are intercepted by the Pyrenees and 

 Alps make the climate of the Mediterranean 

 region very much warmer than that in the same 

 latitude elsewhere. Naples, Italy, has a semi- 

 tropical climate, but it is almost in the same 

 latitude as New York City in the United States. 



Inclination of the Earth's Axis. The inclina- 

 tion of the earth's axis is one of the most 

 important factors in climate. In the torrid 

 zone it causes the movement of the equatorial 

 rain belt north and south, giving nearly every 

 part of the torrid zone an abundance of rain. 

 In temperate zones it causes the alternation 



