Spring – for some people it’s the most beautiful time of the year, when the snows melt, the sun shines brighter and hotter and everything turns green, while for others, it’s hell on Earth. For people with allergies, especially pollen allergies, spring is sneeze season. But as some researchers found, pollen does more than trigger a nasty allergy – it can actually influence the weather.

Pollen is a fine to coarse powder containing the microgametophytes of seed plants; if pollen lands on a compatible female cone, it germinates. However, if it lands inside your nose, it can irritate you and trigger serious allergies. Now, researchers from Texas A&M and the University of Michigan are suggesting that these tiny particles can not only influence your health, but they can influence the weather – especially rain.

The study, published on Monday in Geophysical Research Letters, explains that regular pollen is too heavy to influence the weather, but airborne pollen grains can burst when wet, splitting into subpollen particles. These smaller, subpollen particles can seed clouds and thus lead to increased rain formation.

“What we found is when pollen gets wet, it can rupture very easily in seconds or minutes and make lots of smaller particles that can act as cloud condensation nuclei, or collectors for water,” University of Michigan associate professor Allison Steiner said.

Contrary to popular belief, that all pollen grains break into smaller particles when they come in contact with water, she showed that subpollen particles actually absorb water vapour, encouraging further cloud formation.

They tested for this by getting pollen from several known allergic plants that included pecan, cedar, pine trees, oak, birch, and ragweed. They extracted two grams of pollen and soaked them in water for an hour, after which they made a pollen fragment spray with an atomizer, and sprayed it into a cloud-making chamber. The different types of pollen exhibited a similar behaviour, encouraging cloud formation.

This has significant effects not only for weather patterns, but for the estimated 20% of people with pollen allergies. Additionally, researchers are beginning to think that trees released pollen so rain can come around more often to help trees and plants grow, and this phenomenon can also significantly influence drought spells.

Journal Reference: Allison L. Steiner, Sarah D. Brooks, Chunhua Deng, Daniel C.O. Thornton, Michael Pendleton,
Vaughn Bryant. Pollen as atmospheric cloud condensation nuclei. DOI: 10.1002/2015GL064060


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