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The official term for the smell after it rains (wikipedia.org)
148 points by scorxn on Dec 21, 2009 | hide | past | favorite | 36 comments

I love this smell. I've been fighting with the wife, who claimed it was from asphalt, and I knew it wasn't, since I've smelled it in the middle of nowhere. Turns out, she was actually pretty close, since it's hydrocarbon based.

Somebody should make a perfume based on this. It should be possible to extract the specific oils responsible.

I love this smell too. Smells are emotionally charged to begin with, and this is one of the more powerful ones in my experience. The fact that it's so intermittent and fleeting (small correction to the title: it's the smell after it's just begun to rain) adds to its mystery. Because of that, I kind of hope it doesn't get extracted into a product. Perhaps I'm being too nostalgic, though, sitting in just about the darkest day of winter when it's been -20 for most of the past month...

According to the wikipedia spanish article for Petrichor, they haven't been able to synthesize the smell due to its complex composition of more than 50 substances.

http://www.bristol.ac.uk/news/2007/5384.html made the rounds a while back.

I've always been able to smell something distinctive BEFORE it rains. Don't know what causes that, but I've always thought it was actually change in air pressure that my nose is misinterpreting as a smell.

Are you thinking of a smell with a kind of sharp, metallic or chemical odor, right before a heavy thunderstorm?

If memory serves me, that's due to the voltage between the storm and the ground turning O2 molecules into O3 (ozone), which gets spread around by the storm's winds.

Yeah, I think that describes it pretty well. I don't think I've met anyone else who claims to be able to smell it.

That is, in fact, ozone. You're not alone. I often smell it ahead of big storms as well. Of course, I also smelled it after watching the maple tree in my front yard get zapped 20 feet away with nothing but a window screen and air between my face and $DEITY knows how many kilovolts.

There is some variation in how sensitive people are to individual odors. Picking up the ozone smell before storms seems to be sufficiently rare that a lot of people end up wondering if they're the only one.

Anyway, as I said, the ozone is produced by the electrical activity in the storm--if you're curious, you can get a smell of ozone off of artificial sources of high-voltage electricity as well. Hanging around a Tesla Coil or Van de Graff Generator ought to do the trick.

And hey, look at it this way, it's not the storm itself you're noticing--you're actually smelling lightning. How cool is that?

I've always been able to smell this before a storm as well. I remember when I was a kid and I would tell my parents, friends, whoever, this fact and they would just think I was crazy because no one else could smell it.

I have very poor eyesight, so my hearing and sense of smell are extremely acute.

I can smell if someone is taking antibotics. Maybe I can't smell if anybody is, but I can definitely tell when some are.

Triple J radio in Australia (the government funded "youth" radio station) has a science show with a guy called Dr Karl.


"He holds degrees in mathematics, biomedical engineering, medicine and surgery. He has also studied astrophysics, computer science and philosophy. He has worked as a physicist, labourer, roadie for bands, car mechanic, film-maker, hospital scientific officer, biomedical engineer, TV weatherman, taxi driver and medical doctor."

He also written a ton of books and won an Ig Noble prize for his extensive research in to belly button lint colouring.

He is clearly totally awesome.

Anyway, petrichor is old news to listeners of his radio show, as it's been discussed there numerous times. I highly recommend listening to his podcast, it's full of all sorts of random sciencey stuff presented in an easy to digest way:


In Tamil, we call this 'manvasanai', which literally translates to the smell of earth.


As this involves rain and earth, This poem immediately springs in the mind.

The red earth and pouring rain.

Red earth and pouring rain[1] What could my mother be to yours? What kin is my father to yours anyway? And how Did you and I meet ever? But in love our hearts have mingled as red earth and pouring rain

[Translated by AK Ramanujan (Kuruntokai - 40)


Titled: "What He Said"

On a side note, poetry isn't poetry without proper spacing.

Isn't it strange that so very few smells have their own words to describe them? Supposedly, there are thousands of them, but, with the exception of the formula "it smells like X", almost without exception they don't have proper names.

It's like that tribe in South America somewhere that didn't have words for colors, except in expressions as "colored like the sun" etc.

I think it's exactly because smells are so specific that there are few "general" smell words. It's useful to have a word for "red" since lots of different things are red, and particular shades of red rarely trigger very specific memories. But most of the time, when you smell something, your brain immediately tells you: it's the smell of X, for some specific X.

Presumably this has something to do with the underlying biology. Our colour space is more or less three-dimensional because we have three kinds of receptor in the eye (I'm ignoring the rods here since they aren't involved in colour vision); there are thousands of different kinds of receptor in the nose.

On the other hand, there are many many receptors of each kind in the eye; perhaps shape would be a better analogue for smell. And indeed most of our shape words are for quite specific shapes. There are some broader ones -- smooth, spiky, convoluted, etc. -- but likewise there are a few broader terms for describing smells -- pungent, musky, musty, sweet, etc.

I was about to comment this one, but u already did.

I knew we sprayed bananas and tomatoes to ripen during transit to market but never figured plants used the same technique to delay a process (spraying the ground with an oil) to retard seed germination until it rains. Pretty neat if I read the article correctly.

I don't think that the article infers that but it could be a plausible explanation for the effect of the oil seeping out but it could also be that the moisture seeps out first and then when there is none left the oil seeps out as a last resort.

I remember a childhood friend told me that it was the smell of ozone and I guess it always just stuck. Seems kind of silly now that I think about it.

Not so silly. As elsewhere noted, you will smell ozone when thunder storms are around. The high voltages involved create 03(ozone) from O2(oxygen).

I sort of doubt plants have much to do with the smell. I used to live in a basement apartment with lots of exposed brickwork and a shitty heating system. Every Fall when the temperature started dropping, there would be moisture condensing on the brick, and it would give off the "rainy earth" smell.

Wrong smell!

Depending upon where on earth you live, I think it's possible that you haven't smelled this smell. I now live in the Pacific Northwest. I rarely smell it here, and I miss smelling it. It has to be a hot summer rainstorm, not a winter drizzle.

The smell you're describing, I think, is just "wet earth smell", which isn't nearly as pleasant.

I learnt this (and dozens of other interesting words) years ago from Anu Garg's AWAD mailing list. http://wordsmith.org/awad/archives/0404

I have never heard any one who has ever said that they do not like this smell. I wonder what is it in the that makes us so refreshed and happy. My spirits just sore at this smell.

The likable smell caused by the bacteria http://science.howstuffworks.com/question479.htm

Surely negative ions have got something to do with it?

I thought the smell after it rains was ozone, or perhaps something else oxidizing the inside of my nose.

I have always had a dream of making a perfume out of this smell. Simply refreshing!

What about the smell of asphalt after it rains?

A nice article for the solstice, thank you :)

smells like worms

There was a calvin and hobbes in the 80s that stated the very same.

However, experts believe that "petrichor" will not replace "October rain" as a term of endearment.

I've never heard the term "October rain" before, but had to look it up. Quite a few poems with that title it seems. I thought you were referring to the Gun N' Roses song "November Rain" there for a second :)

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