CLIMATOLOGY OF THE PERUVIAN ANDES 



129 



curve b. Hence, unusual atmospheric disturbances would result 

 in heavier and more frequent showers. 



Turning now to local factors we find on the west coast a re- 

 gional topography that favors a diurnal periodicity of air move- 

 ment. The strong slopes of the Cordillera and the Coast Kange 

 create up-slope or eastward air gradients by day and opposite 



OCT.-MARCH, 1893-'95 

 2 p.m. 



8 a.m. 



APRIL-SEPT., 1893- '95 

 2 p.m. 



8 p.m 



FiO. 79 — Wind roses for Mollendo. The figures are drawn from data in Peruvian 

 Meteorology (1892-1895), Annals of the Astronomical Observatory of Harvard College, 

 Vol. 39, Pt. 2, Cambridge, Mass., 1906. Observations for an earlier period, Feb. 

 1889-March 1890, (Id. Vol. 39, Pt. 1, Cambridge, Mass. 1899) record S. E. wind at 

 2 p. m. 97 per cent of the observation time. 



gradients by night. To this circumstance, in combination with 

 the low temperature of the ocean water and the direction of the 

 prevailing winds, is due the remarkable development of the sea- 

 breeze, without exception the most important meteorological fea- 

 ture of the Peruvian Coast. Several graphic representations are 

 appended to show the dominance of the sea-breeze (see wind roses 



