Fig. 81—Wind roses for Iquique for the summer and winter seasons of the years 1911-1913. The diameter of the circle in each case shows the proportion of calm. For source of data see Fig. [80].
Of highest importance are the effects of the sea-breeze on precipitation. The bold heights of the Coast Range force the nearly or quite saturated air of the sea-wind to rise abruptly several thousand feet, and the adiabatic cooling creates fog, cloud, and even rain on the seaward slope of the mountains. The actual form and amount of precipitation both here and in the interior region vary greatly, according to local conditions and to season and also from year to year. The coast changes height and contour from place to place. At Arica the low coastal chain of northern Chile terminates at the Morro de Arica. Thence northward is a stretch of open coast, with almost no rainfall and little fog. But in the stretch of coast between Mollendo and the Majes Valley a coastal range again becomes prominent. Fog enshrouds the hills almost daily and practically every year there is rain somewhere along their western aspect.
| Fig. 82—The wet and dry seasons of the Coast Range and the Cordillera are complementary in time. The “wet” season of the former occurs during the southern winter; the cloud bank on the seaward slopes of the hills is best developed at that time and actual rains may occur. | Fig. 83—During the southern summer the seaward slopes of the Coast Range are comparatively clear of fog. Afternoon cloudiness is characteristic of the desert and increases eastward (compare [86] ), the influence of the strong sea winds as well as that of the trades (compare [93] B) being felt on the lower slopes of the Maritime Cordillera. |