We’ve all been there at some point or another in our lives. You’re with another person or a group of people, possibly hanging out in the backyard. The clouds proceed to gather, and someone proclaims, “It smells like rain is coming.”
My Nichols ancestors were farmers for generations starting in the Finger Lakes before settling just south of Buffalo in Springville. I’m sure my 4th great grandfather, Louis Nichols, in his 87 years on this planet, threw out the phrase, “It smells like rain is coming”, time and time again. Maybe I even inherited that same nose for weather before I earned my degree in weather (Meteorology) some twenty-one years ago!
Let’s face it though. We know our senses can deceive us sometimes. We also know that when you hear these kinds of comments growing up and think about them when you’re older, you might immediately dismiss some of them as myth, or some sort of distorted misinterpretation of a fact.
But did you ever stop to ponder…Could it actually be true? The answer is….YES!
WHAT GOES INTO THE SMELL OF RAIN ?
That fresh, earthy aroma that hits your nose does have science to back it up. There are times we can smell a rain shower or a thunderstorm coming well in advance of the actual rain. If you’re one of those people, congratulations, you have a sensitive nose!
That sensitive nose is picking up on three things: ozone, petrichor, and geosmin.
Translated: you’re smelling oxygen, the “stuff” in the air being kicked up by raindrops, and bacteria that is wet.
Let’s break it down.
Ozone, unlike oxygen (O2), has three atoms in its molecule, which is why it is called O3.
When oxygen (O2) in the air is heated by a lightning strike during a thunderstorm, ozone is created (O3). The generation of that ozone creates a pungent smell, which when carried by the wind, reaches your nose. If that pungent smell grows even more pungent, you should probably head indoors, as thunderstorms are probably becoming more numerous!
Petrichor is a term coined by two Australian scientists in the 1960s. The term combines a pair of Greek roots: petra (stone) and ichor (the blood of gods in ancient myth). Sounds “meme-worthy” to me!
Anyways, in the study to figure out what’s behind “the smell of rain”, a determination was made that one of the main causes of that distinctive smell is a blend of oils made by some plants during dry spells. The arrival of a downpour after drought causes compounds from those oils that may have accumulated on rocks and in the soil to then be released into the air.
That raindrop is key. A raindrop hitting an uneven surface traps bubbles of air that shoot upwards and burst from the top of the water droplet. These bubbles can float long quite a distance in the air before they pop. When they pop, you smell whatever may be in those bubbles. Basically, you’re smelling the debris in the air that’s kicked up by rain drops. That’s “petrichor”!
Geosmin is a chemical compound that is produced by bacteria that live in soil. Known as actinomycetes, the bacteria secrete a compound when they produce spores. Those spores are sent up into the air when rain lands on the ground. The moist air then sends the compound to our noses which we detect as that great “earthy smell” gardeners love so much.
So the next time you gather together (safely) with friends and someone says, “Hey, it smells like rain,” you can tell them, “Yes, yes it does!”