54 



WEATHER AND CLIMATE 



and snow and thus does not warm the land, water, 

 and air. Moreover, the sun's rays which strike the 

 polar regions are very slanting. Hence the energy is 

 spread over a much larger area, and less heat is re- 

 ceived on any single unit area. In the tropical regions, 

 on the other hand, where the sun's rays are more di- 

 rect, the same amount of energy is concentrated on 

 a smaller area. This is clearly shown by Figure 87. 

 Nearness to bodies of water influences the climate 

 of a given region. Your experiment has taught you 



FIG. 87. DIRECT AND SLANTING SUN RAYS 



The slanting rays from the sun cover more space, and, there- 

 fore, each unit area receives less heat than a similar area under 

 direct rays. 



that water heats more slowly and gives out its heat 

 more slowly than the land surrounding it. This has a 

 tendency to moderate the climate near bodies of water, 

 that is, to make the summers cooler and the winters 

 somewhat warmer. Can you explain why this would 

 follow from what you have learned? Nearness to large 

 bodies of water often determines a fruit growing re- 

 gion, as the slow warming of the water tends to re- 

 tard the plant development in early spring when 

 frosts might harm the buds or blossoms and also its 

 slow cooling makes for a long fall, holding off the 

 frosts and providing ample opportunity for ripening. 

 Do you know of an area near a lake which is a fruit 

 region ? 



A study of the rainfall chart, Figure 80, will show 

 you some ways in which rainfall influences climate. 

 Turn to the chart and compare the rainfall of Cali- 

 fornia with that of Maryland. How do they differ? 

 How does this condition influence the climate in each 

 of these sections? Have you ever been in a greenhouse 

 and noticed the large amount of moisture in the air? 



High relative humidity is a factor which tends to 

 make luxuriant plant growth. The tropical regions 

 in general have high relative humidities, and it is in 

 these regions that we find the jungles of Asia and 

 Africa, where the plant growth is so luxuriant that it 

 can hardly be penetrated by man. 



The climates of places at different elevations above 

 sea level vary, largely because of the decrease in the 

 weight of air, volume for volume. Two cities may be 

 in the same latitude, each near or away from water, 

 and yet have different climates because of differences 

 in their altiudes. Denver, Colorado, and Columbus, 

 Ohio, are two such cities. Can you suggest ways in 

 which the climates of these two cities would vary? 



Ocean currents influence the climate of certain re- 

 gions. The western shores of Europe and of North 

 America are relatively mild as far as climate is con- 

 cerned. Roses bloom in midwinter in the states of 

 Washington and Oregon, and even in Alaska the 

 winters are no more severe, in certain parts, than in 

 the States. The climate of England is much milder 

 than that of Labrador in North America, although 

 both are situated in about the same latitude. What is 

 the cause of these seeming peculiarities in climate? 

 In general, they are due to ocean currents. 



The warm water of the tropics tends to flow out- 

 ward toward the poles. If the earth did not rotate on 

 its axis, these currents would flow nearly north and 

 south, but instead they are deflected northeastward 

 in the northern hemisphere and southeastward in the 

 southern hemisphere. The principal currents of the 

 Atlantic Ocean are the Gulf Stream and the Labra- 

 dor Current. The Japan Current is the most important 

 one of the Pacific Ocean. There are also currents in 

 the Indian Ocean. 



The Gulf Stream flows out of the Gulf of Mexico 

 carrying its warm waters north and east until it 

 strikes the British Islands and then northward to 

 the coast of north Europe. These warm waters greatly 

 moderate the climate of west and north Europe. In 

 a similar manner the Japan Current carries warm 

 waters north and east until they strike the shores 

 of Alaska and are deflected southward to moderate 

 the climate of the entire west coast of North America. 



How does climate affect the life that exists in it? 

 Figures 82-86 illustrate this fact. In desert 'regions 

 the cacti and other desert plants develop leaf ex- 

 posures modified to lose as little water as possible. In 

 tropical climates there is a rank, luxuriant growth of 

 foliage brought about by the high humidity and torrid 

 heat. 



The determining of plant and animal life is clearly 

 seen in the various climatic areas of the United States. 

 Cotton, which needs a warm climate, is raised in the 

 south. Iowa and Illinois are the corn states, and here 



