Smallest pollution particles affect rainfall in the Amazon •

A new study published in the journal Scientists progress found that even extremely small pollution particles resulting from human activities such as burning fossil fuels can significantly alter cloud formation and rainfall patterns in the Amazon.

According to an international team of scientists, oxidation causes small aerosols expelled by factories or automobiles to expand rapidly in the atmosphere, reaching up to 400 times their original size, and thus affecting the formation of raindrops. rain.

“Understanding the mechanisms of cloud and rain formation in the Amazon is a major challenge due to the complexity of the nonlinear physical and chemical processes that occur in the atmosphere,” said the co-author of the study, Paulo Artaxo, professor of environmental physics at the university. University of Sao Paulo (USP) in Brazil.

Examining data collected by instruments aboard a special aircraft monitoring the city of Manaus in Brazil’s Amazon region, Professor Artaxo and his colleagues found that aerosols smaller than 10 nanometers emitted by factories, Power plants or vehicle exhaust constitute a pollution plume over Manaus that is blown by southwest winds.

“Little was known about the role played by these nanoparticles in the precipitation pattern,” said study co-author Luiz Augusto Machado, a meteorology expert at USP.

“The region of Manaus happens to be unique in the world in the sense that it is an open-air laboratory, a mega-city surrounded by forests at a great distance from other cities where we can study how a metropolitan area modifies a environment similar to that of the pre-industrial era.

“It is very difficult to estimate the effect of particles on precipitation due to the large number of atmospheric variables that influence this interaction.”

“So we compared the pollution line with neighboring areas outside the plume. We found that the particles grow rapidly in size. By the time they are 10 km from Manaus they are larger and at 30 km they can grow large enough to become condensation nuclei, affecting the formation of raindrops.

The researchers found that as pollution nanoparticles grow and become condensation nuclei, they can influence precipitation depending on the types of clouds they interact with. If the particles encounter small warm clouds, little precipitation will result. However, if passing through dense, vertical clouds such as cumulonimbi, aerosols could increase precipitation and sometimes even fuel severe storms.

“In other words, even these small particles of pollution influence the precipitation pattern,” Professor Machado concluded.

Through Andrei Ionescu, Personal editor

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