Abstract

The study of fog in Chile is vast. This research has been historically developed at the coast of the Atacama Desert. Here, fog presence is frequent, making it a major feature of the local climate, providing humidity and atmospheric water to this arid environment supporting highly endemic ecosystems. Such studies have contributed to describe fog climatology, its interactions with ecosystems and fog water potential resources. However, research on the distribution and variability of fog and its water potential has been discontinuous in time and space and from different methodological approaches. Thus, we still have a limited comprehensive understanding of the fog along the Atacama for the same period of time, under the same synoptic or regional conditions and with comparable technologies. Furthermore, beyond the Atacama Desert boundaries the study of fog has been very scarce, limiting our understanding of fog water supply in regions that are recently affected by a severe drought, like central Chile. We expand our network from 4 to 20 fog monitoring stations. Each monitoring station is composed of meteorological stations that measure radiation, temperature, relative humidity, wind speed and direction, and fog water yields (by SFCs). This extended network covers from hyperarid environments (18°S) to Mediterranean ones (32°S). The stations are located along the Coastal Cordillera at representative sites with diverse ecosystems. The in-situ measurements are complemented with GOES satellite time series of fog and low cloud data for the period 1995-2022. Our preliminary results show variations in the seasonal cycles of fog, with picks of fog presence in winter and spring (austral) seasons in the extreme north of the network (18° - 23°S), and transiting to maxima in spring and summer in central Chile (30°-32°S). Likewise, stations located to the north of 25° S show a higher seasonal variability than those located to the south of such latitude. This is reflected in the fact that the stations to the north present marked seasons of high and low fog presence, in relation to those located to the south which are more regular. The collected fog water shows a similar seasonal pattern, but with significant variations in volumes influenced by local geographic factors. For example, the highest fog water yields annual average occurs in Alto Patache (20°S) and El Boldo (32°S) with 7 and 4.4 L/m2/day respectively. Conversely, the lowest fog water yield is measured at La Chimba station (23°S) with 0.15 L/m2/day. Fog water yields allow us to understand the relevance of fog water for each ecosystem, contextualizing its dependence on other atmospheric water inputs (precipitation and dew). The network of fog monitoring stations contributes bringing in-situ observations that will allow us to a better understanding of fog latitudinal variations, as well as the regional and local factors that produce it. This knowledge is presented as a key component to understanding the changes in fog under climate change, its implications for the environment, and the necessity to generate conservation strategies for the ecosystems it supports