THE OCCURRENCE OF FOG IN CHILE

Abstract

The topography in Chile is extremely complex and many types of fog are found; both factors complicate the presentation of the data. Despite this, measurements from standard meteorological stations suggest a latitudinal maximum in fog frequency between 35-degrees and 40-degrees-S for coastal stations. This is supported by data from inland stations in Chile and the available observations from Argentina on the Atlantic coast of South America. Along the Chilean coast the average number of days with fog ranges from 3 to 59 per year. The variation in fog frequencies is related to persistent synoptic-scale circulation patterns and to ocean currents.

Specialized fog observations were made at three remote locations in northern Chile to determine fog frequencies on the coastal mountains. The sites were in a very arid region (26-degrees-28-degrees-S) near a large-scale fog-water collection project. Fog frequencies as high as 189 days per year with another 84 days of patchy fog were reported at an altitude of 860 m. These are 3-15 times higher than at low-elevation coastal locations at similar latitudes. Clearly, observations from standard meteorological stations are not suitable for estimating higher-elevation fog frequencies.