It was revealed that the effect of the fog on the natural environment that depends on it is so significant that it can even be seen from space. These environments are currently at risk due to the observed decrease in fog, and in particular coastal fog, following the effects of the global climate crisis
Racheli Vox - Angle, news agency for science and the environment
In our daily life, the fog can be a nuisance for us, whether it is when it covers the road while driving, when our flight is delayed because of it or when it hides from us the view seen from the top of a high mountain. However, in different parts of the world fog has a very high importance, and it is the main source of water for some of the most unique ecosystems.
In a new study Conducted in collaboration with researchers from the United States, China and Namibia and recently published in the journal "Geophysical Research Letters", it was revealed that the effect of the fog on the natural environment that depends on it is so significant that it can be seen even from space. These environments are currently at risk due to the observed decrease in fog, and in particular coastal fog, following the effects of the global climate crisis.
Almost exclusive water source
Fog is created when air cools quickly, and the moisture in the air, that is, the water vapor in it, condenses into microscopic water droplets, in a structure that is actually a low cloud. The new study focused on the phenomenon of coastal fog: fog that forms in areas that are up to several tens of kilometers from the shores of large oceans. Moisture from the ocean reaches these areas, which enables the creation of fogs on cold nights. A familiar example of this is the fog that characterizes the city of San Francisco.
"These fogs dissipate after an hour or two, but this time is enough to provide moisture to the plants and animals that live in the area," says Prof. Yoav Yair, climate researcher and dean of the School of Sustainability at the Interdisciplinary Center in Herzliya. "There are habitats, especially in arid and semi-arid areas, where fog is almost the only source of water." These areas include, among others, the Redwood National Park in California (the forest where the redwood trees grow are the tallest trees in the world), the Atacama Desert in Chile (the driest desert in the world) and the Namib Desert in Namibia. In these and other areas you can find unique species of plants and animals.
Besides the fog's contribution to nature, it is also a source of water for humans: in the Atacama Desert, for example, the residents use fog traps - huge nets that capture the tiny water droplets that make up the fog, allowing the residents to use the water for their needs.
A decrease in the number of foggy nights
In recent years Evidence is accumulating that the coastal fogs are decreasing due to the climate crisis. "The studies show that the increase in the average temperature of the oceans and the atmosphere causes a decrease in the number of nights that are false enough to create fog," says Yair. "During the 20th century there was a decline of almost 33 percent in the number of foggy nights, and this trend is going to continue. This is expected to increase stress in the ecological environments that need a certain number of foggy nights per year - and will get much less of that."
Another factor that affects the amount of fog is the urbanization process, which leads toRising temperatures in urban areas and which reduces the humidity in the air. In urban areas, the fog is also affected by the levels of air pollution: in order for the water vapor in the air to turn into fog, it needs surfaces on which it can condense - and the pollutant particles in the air serve this purpose well. "Ironically, the improvement of air quality results in a decrease in the amount of particles on which fog can form and a decrease in the probability of its formation, at least in urban areas, such as San Francisco," says Yair.
Greener in foggy times
The new research was conducted in the Namib desert, which is recognized by UNESCO as a world heritage site. Nearly 300 different species of animals, over half of which are unique to this region only. Today, fog prevails in the Namib desert in the morning during about 300 days a year.
The fog is very essential to the unique ecosystem in the Namib desert. The plants that grow in the area have developed ways to use the mist water: for example, the Nara plant (Acanthosicyos horridus), whose fruits are a kind of thorny and sweet melons, harvests the water with its stems, and the Welwitschia mirabilis, a low plant that can reach an age of over 2,000 years, uses that So in its thin roots.
The insects that live in Namib also take advantage of the fog water: the Fog Basking beetle, for example, raises its butt into the air, so that the fog water condenses on it and flows from it into its mouth. Another beetle, the Flying Saucer Trench beetle, digs trenches where fog water collects and condenses. Various local animals feed on these beetles, including geckos, snakes, birds and more.
In the new study, two different sites in the Namib desert were examined. The researchers used data on fog levels in the locations studied, collected by local weather stations between 2017-2015, and cross-referenced them with data on vegetation in the area collected by NASA and the United States Geological Survey satellites. , which included optical photographs and information from microwave sensors.
The researchers found a clear connection between the fog levels and the state of the vegetation in both sites throughout the period studied. At the first study site, the values of the optical indices, which accurately recorded the shade of the vegetation (that is, how green it is), were 15 percent higher in foggy periods than in fog-free times, and a similar phenomenon was also observed at the second study site. In addition, the microwave indices, which quantified the mass and water levels in the plants, were 60 percent higher during periods of fog.
In the future, the scientists are interested in expanding the research and examining the effects of the fog over longer periods of time, as well as exploring other areas where the coastal fog is significant, such as Redwood National Park.
Less fog in Israel?
Has there also been a reduction in fog? "Until now, we have not conducted a serious study on the issue of the prevalence of fog in Israel," says Dr. Amos Porat, director of the climatic services department at the meteorological service. However, according to him, despite the lack of established scientific evidence on the subject, there are certain indications that the phenomenon also exists here. From a quick check I conducted at our station in Beit Dagan, there really is an impression that there is a certain decrease," he says. "Furthermore, when I talk to the forecasters who deal with the issue and who have to give a forecast for the fields aviation, they say they have a certain feeling that there may be fewer cases of heavy fog in Israel in recent years."
Porat emphasizes that it is impossible to make definitive statements on the subject without conducting in-depth and serious research, but also notes that such a decline would be logical. "Considering the significant increase in global temperature compared to the global average and the urbanization process, the conditions necessary for the formation of the fog are compromised," he concludes.
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