smell of rain

I’ve always loved the smell in the air when rain falls in summer. To my nose it smells like ‘warm rain’.   Whether it’s landing on concrete, tarmac or soil – it just smells wonderful. Clean. Fresh. Alive.

As a kid I remember going outside to dance in the rain – it was so joyous and free and the feel of the drops, the scent and yes I was likely barefoot. We grew up in a climate that had proper hot African summers. No need for shoes, little ‘flipflops’ were the most we needed.

Only recently did I learn that this smell has it’s own name – petrichor.   It’s named after Greek petros (stone/rock) and ichor (the fluid that flows in the veins of the gods).

Did you ever wonder why you can smell that rain is on it’s way? That particular scent when warm summer rain falls to the dry-baked soil or scorching tarmac.  I remember what the air smelt like before rain and lightning would arrive in the African veldt.

Gardeners can smell when rain is coming. Of course the raindrops themselves have no scent. But moments before the drops land, there’s this lovely fresh and earthy scent that is called petrichor.  Petrichor is a result of ground getting moistened. It was first documented by Australian scientists in 1964.

Petrichor

But what is petrichor?

Petrichor is natural fragrance created by plant oils and actinobacteria.  Actinobacteria are nature’s recyclers. They break down dead or decaying organic matter into simple chemical compounds so that the nutrients can be reused by plants and micro organisms. While they are busy decomposing matter, they release geosmin into the air.  Geosmin is so pungent that our noses can detect even a few parts per trillion of air molecules.

During dry spells, actinobacteria slow down their activity.  But just before rain arrives, the increase in humidity switches on actinobacteria and of course  that means geosmin is released into the air.

Pluviophile

a lover of rain; someone who finds joy and peace of mind during rainy days.

As raindrops plummet to earth, they smash onto porous surfaces like rough concrete and loose soil, they eject geosmin and petrichor compounds into the air. The wind then carries this scent downwind – and that is why you can smell that rain is on its way!

And once the rain finishes and the ground dries out, the actinobacteria slow down their scented molecule production.

Petrichor meaning

Petrichor is the pleasant smell produced when rain falls on dry ground. Thunderstorms release ozone which has it’s own scent. Raindrops release micro-organisms hidden in the soil, mixed with the smell of plant oils and ozone itself: that’s petrichor.

Perfumers even incorporate petrichor into their creations to create a sense of freshness and new beginnings. In India mud is distilled into sandalwood oil to make a precious attar. (It smells gorgeous!)

Geosmin smells like the concrete when the rain hits it.  What’s interesting is that most of us don’t like the taste of geosmin. It’s what gives beetroots their ‘earthy’ flavour.

Pluviophile

Definition (n) a lover of rain; someone who finds joy and peace of mind during rainy days

Add to that the calming effect of raindrops, be they beating a staccato on a tin roof in Borneo at 4pm, or gently tapping your window during night, rain can be immensely  soporific and an antidote to the stress of the previous 18 months.

Here’s a soundtrack to soothe the most frazzled nerves: