CropLink

Can You Smell the Rain?

Image by Pamela Smith

Songs have been written about it. Farmers often proclaim it. Turns out, it is true: You can smell rain events.

Sometimes the nose turns predictive by picking up the scent of ozone. It’s a slightly chemical smell, like when you get a whiff of chlorine bleach or air-conditioner coolant. “In thunderstorms, lightning splits oxygen and nitrogen molecules, which then recombine to form nitric oxide. This is a free radical and can then form ozone,” says Bryce Anderson, DTN senior ag meteorologist. “Enough ozone can smell similar to chlorine, and enough of that smell is a good bet a storm is on the way.”

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Those sweet, fresh, earthy tones that come along with a spring shower bring a slightly different fragrance and even have a scientific name: “petrichor.” A pair of Australian scientists, Isabel Joy Bear and Richard G. Thomas, researched the aroma of rain and, in 1964, coined the term combining a pair of Greek words: petra (stone) and ichor (the fluid that flows from the veins of the gods of Greek mythology).

A 1964 article in Nature titled “Nature of Argillaceous Odour” discusses the distinctive musky smell that comes when rainwater mixes with plant oils. Another compound called geosmin, a metabolic byproduct of certain bacteria, is also emitted by wet soil that adds to what our noses identify as the smell of rain.

More recently, Massachusetts Institute of Technology scientists have used high-speed cameras to determine that raindrops that collide with soil can bubble up in an aerosol. It is thought this action, rather than the rain itself, releases mineral-like aromatics upon the wind.

Science aside, one thing is certain: Nothing smells sweeter than a spring rain falling when it is truly needed.

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