CLIMATE 75 



polar climatic cap is due to the expansion of the land in that 

 hemisphere. The greatest expanse of land lies in the north tem- 

 perate zone. 



Physical Climate. 



This is the climate produced through modification of the solar 

 climate by the physical characters of the earth's surface. The prin- 

 cipal kinds to be considered are: i, The marine or oceanic; 2, the 

 coast or littoral; 3, the continental or interior; 4, the desert, and 5, 

 the mountain and plateau climates. Each of these has its peculiari- 

 ties which in turn influence the distribution of plant and animal life. 

 (See Chapter XXIX.) 



1. Marine or Oceanic Climate. Owing to the slow changes of 

 temperature which the ocean wciter undergoes, the seasonal tem- 

 perature changes are comparatively slight, while the times of oc- 

 currence of maxima and minima are retarded, a cool spring and 

 warm autumn resulting. Relatively greater humidity, cloudiness, 

 and heavier rainfall than is found on the land, are further charac- 

 teristic of marine climates ; and are explained by the greater evap- 

 oration over the sea. In the winter within the middle latitudes, 

 there is excessive precipitation over the oceans, but the continental 

 interiors are relatively dry. Air over the water is also purer and 

 in more active motion than that over the land. 



2. Coast or Littoral Climate. The coastal region shows the 

 transition from the marine to the interior continental type of cli- 

 mate, and may alternately partake of both, according to whether 

 the prevailing wind is from the sea or from the land. The wind- 

 ward coasts are usually well supplied with rainfall, especially in 

 the tropics, while the leeward coasts, notably those in the trade- 

 wind zones, are usually dry ; and the deserts may extend clear 

 to the coast. This is the condition on the west coasts of South 

 America, xA.frica and Australia, The cold shore currents and the 

 prevailing long-shore winds further prevent precipitation. An ex- 

 ception to this general character of wet eastern and dry western 

 coasts in the trade-wind zone is seen in the regions of the monsoons. 

 Thus the west coast of India is abundantly watered by the wet 

 southwest monsoon. A peculiarity of these monsoon countries is 

 the threefold division of the climate such as characterizes India. 

 In the winter little precipitation occurs, and the temperature is lov, 

 the monsoons blowing offshore. Then follows the hot transition 

 period, which in turn is succeeded by the cooler and wet summer 

 season, when the monsoon blows onshore. The monsoons of the 



