All over the world, dust is released into the atmosphere from anthropogenic and natural sources. MIT researchers have now used a simulation to find out how these particles trigger violent thunderstorms.
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Scientists have discovered a new mechanism by which aerosols can amplify thunderstorms in tropical regions.
Photo: MIT
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Researchers have long known from observations of the earth’s atmosphere that thunderstorms occur more frequently and are stronger in polluted air and high aerosol concentrations than under comparable climatic conditions with a clean atmosphere. There are more lightning strikes along shipping routes because freighters emit large amounts of particles into the atmosphere. As a comparison, scientists use the surrounding ocean without ships. And violent tropical thunderstorms usually build up over land, where there are many particles in the air from natural or anthropogenic sources. However, the mechanisms behind this connection were previously unknown.
Now a working group at the Massachusetts Institute of Technology (MIT) in Cambridge has found an explanation for the phenomenon. Using mathematical simulations of cloud dynamics, they show that high aerosol concentrations increase thunderstorm activity by increasing the water content in the air surrounding clouds. This new mechanism could be integrated into weather and climate models in order to predict how the thunderstorm activity in a region will change if more aerosols enter the air due to anthropogenic causes.
The MIT researchers provide another argument for avoiding such emissions. “It is possible that by removing pollution in places, there will be fewer thunderstorms and fewer storms,” said Tim Cronin of MIT. Overall, the study shows that humans influence the climate in a way that was previously not considered.
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Simulation of cloud formation on the computer
Background: Aerosols are created through anthropogenic processes such as the emissions from internal combustion engines, emissions from factories or the burning of wood. But natural phenomena such as volcanic eruptions or dust that is blown up by the wind lead to the entry of small particles into the atmosphere and thus to aerosol formation.
Water vapor from the environment can condense on the surfaces of the particles. Fine droplets arise and form a cloud. They aggregate, form larger droplets, and eventually fall to the ground as rain. However, if the concentration of particles is high, fine droplets will form, but will not rain down. Why there are strong thunderstorms in this scenario was unknown.
MIT engineers used an idealized system for their mathematical modeling. It describes the dynamics of clouds in a cube with an edge length of 128 kilometers above the tropical ocean. Various parameters were changed in this unit of volume to see how cloud formation changes if the aerosol concentration increases. However, this alone could not explain the formation of strong thunderstorms.
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