Fog collection and its relationship with local meteorological variables in a semiarid zone in Chile

Abstract

In semiarid and arid zones, fog is considered an important alternative water source. The Southeast Pacific anticyclone and the cold Humboldt Current that characterize the north of Chile promote the formation of stratocumulus along the coastline. The thermally induced winds move these clouds eastwards favoring the formation of fog in the high hills of the Coast Range. The goal of this work is to characterize the fog water collected by a standard fog collector and its relationship with local meteorological variables. We found that the collected water is seasonally dependent, larger in summer than in winter. The mean diurnal cycle in autumn, summer and winter presents two maxima, at the early morning and late afternoon, meanwhile in winter it presents smooth variations during the day. The wind regime was compatible with land-sea circulation. The monthly mean temperature reached the maximum value in March and the minimum value between July and September, whereas the mean monthly daily temperature amplitude was larger in winter than in summer. The minimum values of relative humidity were achieved in the winter months. The fog water collection varies from zero to a maximum value that increased with wind speed, and mainly occurred with SW and NE winds. The fog index (FI) was defined as the percentage of foggy-days per month for which the water collected is greater than one liter. We found that FI follows the same trend as the monthly collected water, and decreases with the mean monthly daily temperature amplitude.