Abstract
Fog water represents an alternative, abundant and currently unexploited fresh water resource in the coastal Atacama Desert (~20°S). Here, the stratocumulus clouds meet the Coastal Cordillera, producing highly dynamic advective marine fog, a major feature of the local climate that provides water to a hyper-arid environment. One of the main issues that arises in harvesting fog water is our limited understanding of the spatial and inter-annual variability of fog clouds and their associated water content. Here we assess the role of regional-wide El Nino Southern Oscillation (ENSO) forcing on local inter-annual fog-water yields along the coast of Atacama. We contrast 17 years of continuous fog-water data, with local and regional atmospheric and oceanographic variables to determine the link between them and the inter-annual dynamics of fog in northern Chile. Sea surface temperature (SST) in ENSO zone 1 + 2 shows significant correlations with offshore and coastal Atacama SST, as well as with local low cloud cover and fog water yields, which go beyond the annual cycle beat, exposing a potential causal link and influence of ENSO on fog along the Atacama. On the inter-annual time scale, we found that when ENSO 3 + 4 zone SST, specifically during summer, overcome a > 1°C temperature threshold, they incite significantly higher summer fog water yields and explain 79% of the fog variability. Furthermore, satellite images displaying regional extent Sc cloud and fog presence during ENSO extremes reveal higher cloud abundance during El Nino at this latitude. However, 75% of the yearly fog water is collected during winter, and does not appear to be affected in a significant manner by Pacific oscillations. Thus, our results suggest that the utilization of fog as a fresh water resource may be sustainable in the future, regardless of ENSO-induced variability in the region.
Highlights
Due to the extremely low levels of precipitation in the costal Atacama, there are very limited and in some cases no fresh water sources available (Núñez and Varela, 1965)
On the inter-annual time scale, we found that when El Niño Southern Oscillation (ENSO) 3 + 4 zone Sea surface temperature (SST), during summer, overcome a > 1°C temperature threshold, they incite significantly higher summer fog water yields and explain 79% of the fog variability
Our results suggest that the utilization of fog as a fresh water resource may be sustainable in the future, regardless of ENSO-induced variability in the region
Summary
Due to the extremely low levels of precipitation in the costal Atacama, there are very limited and in some cases no fresh water sources available (Núñez and Varela, 1965) (e.g., the city of Iquique has an average precipitation rate of 0.6 mm year–1, DMC, 2016). Fog water yields in the coastal Atacama Desert average over 7 L m–2 day–1 (Larraín et al, 2002; Cereceda et al, 2008a), which afford a water supply based on fog for local settlements (fishing villages) and low scale economics activities (Osses et al, 2000; Schemenauer et al, 2007). One of the main issues that arise in harvesting fog water is our limited understanding of the spatial and inter-annual variability of fog clouds and their associated water content in the Atacama. These clouds are the result of the regional-scale interaction between oceanic, atmospheric and local-scale geographic factors, which have remained mostly unattended when studying fog water content
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