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When people say they can smell a storm coming, they're right. Weather patterns produce distinctive odors that sensitive noses sniff out. This year's peculiar weather patterns—such as drought in the Midwest and a "super derecho" of thunderstorms earlier this summer—are no exception. In fact, as the rains return after a dryspell, many of these odors are stronger than ever. So, what are the scents of a summer storm? Here's a breakdown of three common odors:
—Oh, ozone
Before the rain begins, one of the first odors you may notice as winds pick up and clouds roll in is a sweet, pungent zing in your nostrils. That's the sharp, fresh aroma of ozone—a form of oxygen whose name comes from the Greek word ozein (to smell). Tropospheric chemist Louisa Emmons at the National Center for Atmospheric Research explains that ozone emanates from fertilizers and pollutants as well as natural sources. An electrical charge—from lightning or a man-made source such as an electrical generator—splits atmospheric nitrogen and oxygen molecules into separate atoms. Some of these recombine into nitric oxide, and this in turn reacts with other atmospheric chemicals, occasionally producing a molecule made up of three oxygen atoms—ozone, or O3. (Most atmospheric oxygen is made up of two atoms—O2.) The scent of ozone heralds stormy weather because a thunderstorm's downdrafts carry O3 from higher altitudes to nose level.
—Petrichor potpourri
Once the rains arrive, other odors come with them. Falling water disturbs and displaces odoriferous molecules on surfaces, particularly on dry ones, and carry them into the air. If you happen to be near vegetation, these molecules may come from plants and trees. For city dwellers, these odorants rise up from concrete and asphalt. Some are fragrant, others foul.
There's a name popularly ascribed to this range of post-precipitation scents: petrichor. Petrichor was first described in 1964 by mineralogists Isabel Joy Bear and R. G. Thomas of Australia's Commonwealth Scientific and Industrial Research Organization. As they defined it, it occurs when airborne molecules from decomposing plant or animal matter become attached to mineral or clay surfaces. During a dry spell, these molecules chemically recombine with other elements on a rock's surface. Then when the rains came, the redolent combination of fatty acids, alcohols and hydrocarbons is released.
—Damp earth
After a storm has moved through, what's often left is an earthy-musty whiff of wetness. This is the aroma of geosmin, a metabolic by-product of bacteria or blue-green algae. Geosmin can be a comforting call to gardeners eager to dig in the dirt, but it's less beloved when it contaminates wine or drinking water, leaving a damp stench.
Why an aroma at all?
All these chemicals stirred up by the weather can carry messages. Some biologists suspect that petrichor running into waterways acts as a cue to freshwater fish, signaling spawning time. Microbiologist Keith Chater at the John Innes Center in England has proposed that geosmin's fragrance may be a beacon, helping camels find their way to desert oases. In return, the bacteria that produce geosmin use the camels as carriers for their spores.
But do these smells send meaningful messages to humans? Anthropologist Diana Young at the University of Queensland has studied the traditions of aboriginal people in Australia's Western Desert. There, the first rains before wet wintry and summer months are an important event, mingling the sweet odors of damp gum leaf oils, eucalyptus, animal waste and dust. The rains bring game such as kangaroo and emu, quench thirst and transform the red desert into a verdant landscape. Young says that to these people the smell of rain is linked to the color green, a connection she calls "cultural synesthesia." In fact, many of these Aboriginal peoples manufacture their own perfume with plant and animal fats and rub it onto their bodies, a symbolic connection of body and landscape. The odor is believed to be protective and cleansing, linking present generations to their ancestors.
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13 Comments
Add CommentI associate a coming rain with a smell close to the smell from rain drying on warm macadam, might that be ozone? We may least understand the sense of smell. I do wonder what a dog's world must be like; where we see so much, they instead smell so much, and I'm sure most all it is useful to them, and perhaps as rich a world as our visual world, or even our linguistic world.
Reply | Report Abuse | Link to thisyes, sometimes I can smell the rain coming approx 15 to 30 minutes ahead; for me it is a certain change in the air, something that changes within a few minutes, a bit fresher, and only when I'm outside. I've also noted over the years that different people smell this differently, I guess depending on where they grew up (sensory education).
Reply | Report Abuse | Link to thisAlso, where I come from, when someone wants to express that he really doesn't like someone, he says "I simply can't smell (stand the smell of) him".
More astonishing, women's sense of smell... taking the pill or not... marriages breaking up when she goes off the pill and her natural sense of smell returns and suddenly she "couldn't smell him" anymore. I've predicted certain couples breaking up when one of them stopped smoking (because the sensory smell perception returned). It fascinated me for years. Did all kinds of experiments too, some to astonishing effect, because it gave me unexpected insights into something I was working on at the time and which had in itself nothing to do with smell, but all with sensory perception as a counterweight to cognitive processes. (As you probably see, I get all excited over the memory of those experiments, I can virtually smell those times again <g>)
About what the previous commenter mentions: when I lived in NY I had a rescued sledge dog who could smell snow approx 12 hours ahead. I didn't tell anyone how I did it but when I said it would snow in half a day, it would. I build quite a reputation on my dog's sense of how snow smells. <g>
So yes, I can smell the rain coming (sometimes), I can also sometimes smell a coming change in weather towards heat when the change will be significant enough. I guess it's the same process as smelling rain but in reverse. And I do believe that dogs can "smell" all kinds of natural phenomena, from snow to cancer (quite proved by now, starting with Freud's dog when he got terminally ill), and that smell is a VERY underrated and badly underresearched sense, also in humans.
So great to read this article, much appreciated.
Coming home from Muriwai to Auckland (New Zealand) the sky was blue but I could smell rain. I knew there was a big rainstorm somewhere. Once we got on to the main road, I saw a cloud, a long way off and near the horizon, with rain falling from it, although the rest of the sky was blue.
Reply | Report Abuse | Link to thisSure enough, on the news that evening there had been a heavy rainstorm over a "Big Day Out" pop music open air concert south of Auckland, and the place was awash.
The smell of rain had come at least twenty miles.
Yes! The smell of ' wet floor ' is very strong!
Reply | Report Abuse | Link to this"sled" dog
Reply | Report Abuse | Link to thisah, we foreigners... chien de traîneau / sledge dog... we shouldn't always trust our translation skills I suppose... could you look it up for me in your words book?
Reply | Report Abuse | Link to this
Reply | Report Abuse | Link to this"Humans can distinguish more than 10,000 different smells (odorants), which are detected by specialized olfactory receptor neurons lining the nose.... It is thought that there are hundreds of different olfactory receptors, each encoded by a different gene and each recognizing different odorants. Each of the hundreds of receptors are encoded by a specific gene. If your DNA is missing a gene or if the gene is damaged, it can cause you to be unable to detect a certain smell."
(Source: "Molecular Biology Of The Cell")
In order for us to smell something, that "thing" must be giving off molecules through the air that enter our nasal passage; where the special neurons at the top of the nasal passage are triggered to identify the odor, scent, fragrance, smell,etc. The Human's sense of smell as a survival tool is perhaps one of the best reasons why we're equipped with it - I can detect even the slightest nuance of "badness" in milk, food, etc.
I'm conjecturing that how it works, is once we match a smell to it's source, it's logged into our "smell memory file" for the duration; for our reference purposes. It would be so fascinating to be able to visually view that file!
In the opening paragraph of this Scientific American article, it states: "Weather patterns produce distinctive odors that sensitive noses sniff out." It is, perhaps more appropriate to say that rain exudes droplets of water that can travel great distances, prior to the full rainfall commencing - and that those droplets consist of molecules that any nose equipped with the ability to detect & identify the rain droplet molecule (not just noses that are sensitive); can detect. I marvel at this phenomena just now being recognized by Scientific American - the Human's propensity to detect the "coming of rain" beforehand
has been well-known for eons; and subsequently, was not a subject of such recent research as to warrant this article as being newsworthy.
It seems as though they were looking for filler articles for their publication. It would behoove Scientific American to dedicate the editorial space, as well as their efforts, to investigating subjects such as "Why do droughts exist on a planet that has been well-versed for decades, on the subject of making rain happen?"
sorry to be so slow, the correct expression is SLED dog then and it's noted for the future
Reply | Report Abuse | Link to this"dedicate ... space... efforts, to investigating subjects such as "Why do droughts exist on a planet that has been well-versed for decades, on the subject of making rain happen?"
Reply | Report Abuse | Link to thisOr if there is a "possibility of intelligent life in politics"
jctyler - I said nothing about "dedicating space efforts" to anything; nor did I even remotely mention anything about politics & intelligent life. Talk about coming out of left field! It truly escapes me how or why you made those two leaps, but I'm sure you've got your reasons, no?
Reply | Report Abuse | Link to this"I said nothing about "dedicating space efforts" to anything"
Reply | Report Abuse | Link to thisOf course you didn't say that. You said: "It would behoove Scientific American to dedicate the editorial space, as well as their efforts, to investigating subjects such as "Why do droughts exist on a planet that has been well-versed for decades, on the subject of making rain happen?"
which quote I took a step further to say (and the dots indicated where to fill in): "wouldn't it behoove Scientific American to DEDICATE the editorial SPACE, as well as their EFFORTS, to investigating subjects such as the "possibility of intelligent life in politics" to better understand why we have these abnormal droughts in the first place?"
Excuse me for having believed that we were pulling on the same side of the rope, and irony explained is generally a waste of time, but to soothen your wounds, I expressed a bit too subtly it seems the general belief in my field that the abnormal droughts of the present are a consequence of idiotic politics or government by idiots if you wish.
But since you take this so seriously, making rain on demand has been wishful thinking since humans experienced droughts; not a single method ever worked more than erratically over a very small area. And a good thing it is. I hate to think what the climate would be if those idiots in politics had access to rain-making on a grand scale? Only look at what happens when they redirect rivers on a large scale in Russia or Tibet, the latter probably offering a prime trigger for a serious nuclear war in the region.
Also, I suggest the collected works of Mr J. Cleese and associates on "reading between the lines".
But this is far too much explaining off-topic (which is why I already used the filler dots) and I will not react to more of the same.
Coming from the North of England , we are getting far too used to smell of rain! However,in my experience, the "smell" of ozone is not the gas itself(odourless according to most sources), but a cocktail of nitrogen oxides produced by HV discharges, so IF you're down wind of a decent storm you will smell it.
Reply | Report Abuse | Link to thisjctyler - I thank you for clarifying that - after I read your explanation, I looked inward; shaking my head at my own lack of perception .... kinda scary; hope I'm not coming down with the "dumbing-down" syndrome that affects so many Americans today. I thought that since I don't pay for, own, or watch cable TV, that I was safe from that affliction. But man! I clearly didn't read into what you were saying - ooops! Sorry! I shall follow your gracious suggestion and check out the collected works of Mr. J. Cleese & Associates.
Reply | Report Abuse | Link to thisThat said, I reckon that we perhaps are pulling on the same side of the rope, as you say - (I like that better than the "fence" analogy!). I say this because I do coincide with your way of thinking regarding the politics, etc. Not being certain who the "they" actually encompasses, I usually refer to them in a general way as the "Shot-Callers". However, since I fully empathize with your horror at the thought of "them" getting their paws on the stuff that would enable them to control the weather - I've thought it over carefully, and it took only a brief moment of indecision to make the right choice. Without going
into further explanation here, may I respectfully suggest that you pull up the website of an organization called "Weather Modification, Inc."
You'll find all the information I'm speaking about
in their site.
Thanks for not being too snotty and derisive when you provided clarification for me, jc; you got class, kid.