224 INTERACTION BETWEEN THE ATMOSPHERE AND THE OCEANS 



understood, and in the earlier chapters emphasis has been placed on dis- 

 cussion of these processes. Heat exchange and evaporation have been 

 dealt with, and the conditions that further or reduce these processes have 

 been described. The stress of the wind has been discussed, and the rela- 

 tion of the ocean currents to the prevailing winds has been dealt with. 

 As far as the atmosphere is concerned, only the very lowest layers that are 

 in immediate contact with the sea surface have been considered, but it 

 will now be attempted to point out some of the larger features of the 

 atmosphere that are directly related to the distribution of land and sea. 



The Oceans and the Climate 



The influence of the oceans on the climate has long been recognized. 

 The two most extreme types of climate that are related to the distribution 

 of land and sea are the continental and the maritime. The continental 

 type, which is found over great inland areas, is characterized by warm 

 summers and cold winters and, therefore, by a wide range in temperature 

 between summer and winter, and by warm days and cool nights, and thus 

 by a wide range between day and night. Mostly, it is also characterized 

 by little cloudiness and little precipitation. In contrast, the maritime 

 climate, which prevails over the oceans, is characterized by a small annual 

 variation in temperature, by cool summers and mild winters, by a very 

 small range of temperature between day and night, and often by great 

 cloudiness and considerable precipitation. In middle latitudes the gen- 

 eral circulation of the atmosphere is directed from west to east, and east 

 coasts are, therefore, greatly under the influence of winds blowing from a 

 large continent, whereas west coasts are under the influence of onshore 

 winds from the sea. In these latitudes, therefore, the east coasts have a 

 more continental climate and the west coasts a more maritime climate. 

 In equatorial regions the circulation is from east to west and the climatic 

 conditions of the coasts are reversed, but the differences are small. 



The great difference between the continental and the maritime cli- 

 mates of middle and high latitudes is mainly due to the fact that the solid 

 earth, in contrast to the ocean, does not store any appreciable amount of 

 heat. Only the very surface of the land is subjected to temperature 

 changes, and the surface temperature is, therefore, greatly raised in 

 summer when heat is received from the sun, and greatly reduced in winter 

 when excessive loss of heat by radiation takes place. Similarly, the 

 temperature is increased during the day and reduced during the night. 

 The ocean, on the other hand, can store large amounts of heat, because in 

 summer processes of vertical mixing distribute the heat absorbed from the 

 sun over a relatively thick layer of water, the temperature of which will be 

 only moderately increased. In winter the loss of heat similarly takes 

 place from a considerable layer of water, for which reason the temperature 

 decrease of the surface of the sea will be small. If processes of mixing 



