CLIMATOLOGY OF THE PERUVIAN ANDES 



125 



THE CLIMATE OF THE COAST 



A series of narrow but pronounced climatic zones coincide with 

 the topographic subdivisions of the western slope of the country 

 between the crest of the Maritime Cordillera and the Pacific Ocean. 

 This belted arrangement is diagrammatically shown in Fig. 75. 

 From the zone of lofty mountains with a well-marked summer 

 rainy season descent is made by lower slopes with successively 



ZONE OF 



ZONEOF FOG-i 



ZONE OF DESERT PLAINS 



ZONE0FSTEEP 



ZONE OF LOFTY MOUNTAINS AND 



COASTAL TER- 



COVERED MOUN- 





RAIN AT INTERVALS OF MANY YEARS 



VALLEYS 



PLATEAUS /^>^!!! 



RACES 



RAIN ONCE 



TAINS 



RAIN AT INTER- 







YEARLY RAINS 



FREOUENT RAINS IN^^V^-^3^ 

 S U MHERJiaNTHS^^^ 



IN MANY 



VALS OF 5-10 







I»^ '" 



YEARS 



YEARS 5,000' 











PROFILE OF MAJES VALLEY 



"" 





Fig. 75 — Topographic and climatic provinces in the coastal region of Peru. The 

 broadest division, into the zones of regular annual rains and of irregular rains, occurs 

 approximately at 8,000 feet but is locally variable. To the traveler it is always clearly 

 defined by the change in architecture, particularly of the house roofs. Those of the 

 coast are flat; those of the sierra are pitched to facilitate run off. 



less and less precipitation to the desert strip, where rain is only 

 known at irregular intervals of many years ' duration. Beyond lies 

 the seaward slope of the Coast Bange, more or less constantly 

 enveloped in fog and receiving actual rain every few years, and 

 below it is the very narrow band of dry coastal terraces. 



The basic cause of the general aridity of the region has already 

 been noted ; the peculiar circumstances giving origin to the variety 

 in detail can be briefly stated. They depend upon the meteorologic 

 and hydrographic features of the adjacent portion of the South 

 Pacific Ocean and upon the local topography. 



The lofty Andes interrupt the broad sweep of the southeast 

 trades passing over the continent from the Atlantic ; and the wind 

 circulation of the Peruvian Coast is governed to a great degree 

 by the high pressure area of the South Pacific. The prevailing 

 winds blow from the south and the southeast, roughly paralleling 

 the coast or, as onshore winds, making a small angle with it. 

 When the Pacific high pressure area is best developed (during the 

 southern winter), the southerly direction of the winds is empha- 



