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Atmosphere

Seeders of clouds

Pollen grains can contribute to cloud formation and increase rainfall

Joseph Xu, Michigan Engineering Communications & MarketingPollen grains can contribute to cloud formation and increase rainfallJoseph Xu, Michigan Engineering Communications & Marketing

A group of researchers from the University of Michigan, in the United States, has discovered that pollen can do more than disperse the genetic material of plants (and trigger allergic reactions in thousands of people around the world). The minuscule, wind-borne capsules can help to form clouds and disperse them through the atmosphere, increasing the incidence of rain and influencing global climate. It has long been known that these tiny grains, suspended in the air, often break up into even smaller pieces that can produce allergic responses – like hay fever – when in contact with the human body. In a laboratory, the researchers investigated whether atmospheric humidity could be responsible for making pollen break apart. They studied pollen from the trees that release the most copious amounts of these particles in the United States: oak, walnut, birch, cedar, pine, as well as ragweed. Apparently, their pollen grains quickly break up into smaller particles when in contact with water (Geophysical Research Letters, May 11, 2015). To check whether they could contribute to cloud formation, the researchers subsequently pulverized the moist pollen fragments inside a chamber that simulates the Earth’s atmospheric conditions. They observed that the particles acted as condensation nuclei, or water collectors, which lead to cloud formation.

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