The organic particles present in the clouds could contribute to floods and winter storms, because of their influence on ice formation: this is what an EPFL study shows. Scientists call for an update of climate and meteorological models.
The clouds are formed from particles in the atmosphere. Extreme meteorological events – such as floods or snowstorms – are linked to the production of large quantities of ice in nebulosities, said the Federal Polytechnic School of Lausanne (EPFL) on Monday in a press release.
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Floating in the air, certain organic particles, such as pollens, bacteria, spores or vegetable materials, are particularly inclined to promote ice formation inside the clouds.
“This ice is at the origin of most precipitation on our planet, because it falls very quickly from the sky. Massive ice formations are also associated with extreme weather events,” explains Athanasios Nenes, who led the study with the postdoctrant researcher Kunfeng Gao.
“In view of our discovery, the weather and climatic models must imperatively take into account organic particles, especially since we expect to find in greater quantities with global warming,” added the researcher, quoted in the press release.
Indeed, current models do not consider the effects of these particles, any more than their cyclic nature. In fact, they potentially miss important clouds of clouds and precipitation factors in their current and future forecasts.
Mont Chelmós, a case study
The study analyzed air samples and their biological content, taken from Mont Chelmós, in an Alpine region in Greece. At a maximum altitude of 2,350 meters, the summits experience frequent cloud coverage throughout the year and are subject to the influence of organic emissions from the Alpine forest below.
During the day, while temperatures go up, the woods release pollens, bacteria, mushroom spores and vegetable materials. The emissions reach their peak at noon, when the sun is at the zenith, and are at the lowest during the night: “We have discovered that the number of particles likely to form an ice nucleus relating to the quantity of biological particles, and that the two show a strongly correlated daytime periodicity”, underlines Kunfeng Gao.
Scientists have used a full battery of cloud radars, aerosol lidars, drones, balloons and direct air samples-in the presence or not of clouds-to reach a new level of detail. These results are published in the journal Climate and Atmospheric Sciences.
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