Atmospheric water collection across diverse climates along the Chilean coast: unraveling synoptic to local drivers of fog harvesting

The 3000 km long coast of Chile, characterized by a steep mountain range, interacts almost everywhere with the Southeast Pacific stratocumulus (Sc) low clouds deck, producing narrow but extensive fog banks. This long but narrow fog belt crosses diverse climates such as hyperarid (18°- 23°S), arid (23°- 28°S), semi-arid (28°- 31°S), mediterranean (31°- 34°S), and temperate (34° - 37°S), being essential for unaccountable ecosystem types and a virtual water resource to be tapped. In this work, using an extensive network of meteorological stations and standard fog collectors, combined with remote sensing observations and a numerical fog collection model, we characterize the fog water collection at multiple temporal scales, focusing on the physical conditions that allow this collection at local and larger spatial scales. Preliminary results show that the annual cycle of fog water collection along Chilean coast is closely related to the spatial variability of the thermal inversion strength across the seasons, which is the main controller of the formation of the Sc-fog cloud. Our observations taken in hyperarid climatic zones (18° - 23°S) show the highest seasonal oscillation, with peaks in winter-spring. Over arid and semi-arid climatic zones (23° - 28°S), the fog collection cycle is more constant throughout the year, showing a low seasonal oscillation. Contrary to hyperarid climatic zones, the mediterranean and temperate zones (28° - 37°) show water harvesting peaks over the summer with larger seasonal oscillation than (semi-)arid climates. The fog harvesting diurnal cycles in all climates show a decrease at midday associated with the decrease of the Sc-fog cloud presence. The maximum peaks of water collections are related to fog type being at night during advective fog events (higher liquid water content) and in the afternoon during orographic fog events (higher wind speed). In terms of water yields, these are influenced by the local conditions of the site, especially by wind speed, altitude and distance from the coast. However, the highest water collection volumes (yearly, monthly and diurnal) are found in the hyperarid and arid climatic zones (7 to 3 L m-2 d-1 in average respectively), which is consistent with the frequency of Sc-fog presence (50% in the hyper-arid and 30% in the arid). These zones are characterized by having the most fragile ecosystems and population living under a constant water scarcity. Our fog harvesting observations gathered through the largest fog monitoring network on Earth allow us for the first time to assess fog harvesting as a valuable resource in diverse climates. This network constitutes a key tool for understanding the regional and local dynamics of fog collection under a climate change context, as well as to understand its role in ecosystem conservation.