Strong smell of "rain"

[Weather-history]

Really strong smell of "rain" this morning. It hasn't rain for sometime and the light spotty rain is really giving off that distinctive "rain" smell.

[Coast]

 

 

Most people notice a distinctive smell in the air after it rains. It's frequently linked with spring, as the smell of fresh cut grass is associated with summer. You'll find it in a lot of poetry and also on many inspirational lists of things to be happy about. But what causes it?

 

As it turns out, the smells people associate with rainstorms can be caused by a number of things. One of the more pleasant rain smells, the one we often notice in the woods, is actually caused by bacteria! Actinomycetes, a type of filamentous bacteria, grow in soil when conditions are damp and warm. When the soil dries out, the bacteria produces spores in the soil. The wetness and force of rainfall kick these tiny spores up into the air where the moisture after a rain acts as an aerosol (just like an aerosol air freshener). The moist air easily carries the spores to us so we breathe them in. These spores have a distinctive, earthy smell we often associate with rainfall. The bacteria is extremely common and can be found in areas all over the world, which accounts for the universality of this sweet "after-the-rain" smell. Since the bacteria thrives in moist soil but releases the spores once the soil dries out, the smell is most acute after a rain that follows a dry spell, although you'll notice it to some degree after most rainstorms.

 

Another sort of smell is caused by the acidity of rain. Because of chemicals in the atmosphere, rainwater tends to be somewhat acidic, especially in urban environments. When it comes in contact with organic debris or chemicals on the ground, it can cause some particularly aromatic reactions. It breaks apart soil and releases minerals trapped inside, and it reacts with chemicals, such as gasoline, giving them a stronger smell. These reactions generally produce more unpleasant smells than bacteria spores, which is why the after-the-rain smell isn't always a good one. Like the smell caused by the bacteria spores, the smell of chemical reactions is most noticeable when it rains following a dry spell. This is because once the chemicals on the ground have been diluted by one downpour, they don't have the same reaction with the rainwater.

 

Another after-the-rain smell comes from volatile oils that plants and trees release. The oil then collects on surfaces such as rocks. The rain reacts with the oil on the rocks and carries it as a gas through the air. This scent is like the bacteria spores in that most people consider it a pleasant, fresh smell. It has even been bottled and sold for its aromatic qualities! These are a few common rain smells, but there are also all sorts of other scents after it rains. There is lots of aromatic material that the moisture and impact of rain can stir up, and the moist atmosphere following a downpour is particularly good at carrying these particles through the air. So, when you talk about the after-the-rain smell with a friend, you may mean one thing while your friend is thinking of something else. You'll both agree, however, that the air has a much stronger aroma to it after a good rain

 

 

 

http://science.howstuffworks.com/nature/climate-weather/atmospheric/question479.htm

[4wd]

I think that piece is not necessarily about the same thing, I find you can smell rain before it rains (but some of the aromas may travel on the wind).

Also it's not  'after' a rain event but when the first spots begin to fall that the smell is strongest.

It needs to have been dry for a few days beforehand too.

[laserguy]

"For now I smell the rain, and with it pain, and it's headed my way". Led Zep- 'Ramble On'! I can smell rain here,too. But predictably it's all fragmented and looks like another sunny-ish day to come.

[Gray-Wolf]

You'll not smell it over winter though! Cold temps lead to 'no smell' ( in my world) and only as it warms into spring can you again smell the Earth.

[nitro_deluxe]

You'll not smell it over winter though! Cold temps lead to 'no smell' ( in my world) and only as it warms into spring can you again smell the Earth.

Good point Gray-Wolf - perhaps the overpowering odour of decaying leaf, flora and fauna matter takes over the senses as well?Certainly noticeable in more wooded areas, those days when a walk perhaps admiring the ever changing colours, actually transpires

[Bobby]

I love that smell, Petrichor they call it.

 

http://en.wikipedia.org/wiki/Petrichor

 

The term was coined in 1964 by two Australian researchers, Bear and Thomas, for an article in the journal Nature. In the article, the authors describe how the smell derives from an oil exuded by certain plants during dry periods, whereupon it is absorbed by clay-based soils and rocks. During rain, the oil is released into the air along with another compound, geosmin, a metabolic by-product of bacteria, which is emitted by wet soil, producing the distinctive scent; ozone may also be present if there is lightning.In a follow-up paper, Bear and Thomas (1965) showed that the oil retards seed germination and early plant growth. This would indicate that the plants exude the oil in order to safeguard the seeds from germination under duress

[Methuselah]

Good point Gray-Wolf - perhaps the overpowering odour of decaying leaf, flora and fauna matter takes over the senses as well?

Certainly noticeable in more wooded areas, those days when a walk perhaps admiring the ever changing colours, actually transpires

Or, in London's case, the traditional spring-time aroma of previously freeze-dried Staffy crap.