I went out for a brief walk this afternoon. It was raining, but not so hard you needed an umbrella (I hate umbrellas anyway). And so very strong, the smell of rain.
I remember once reading out a poem of mine and having someone come up after the reading and note that I'd used the phrase 'the smell of rain'. I couldn't tell if he liked it or was simply taking the mickey (the latter, I suspect, as he was a very 'cool' poet and I am, manifestly, not).
I wondered about the smell. To me it's always been obvious. But today I decided to go and find, and here, via the ABC and CSIRO, is some hard data. The common rain smell comes from a gas called petrichor. Apparently, volatiles evaporate from plants and are absorbed by rocks, concrete etc. When the rain hits the rock, the volatiles are released into the atmosphere. That's why I can particularly smell it wandering along concrete paths and past sandstone walls.
If it's good enough for CSIRO, it's good enough for my poem.
Now to use petrichor in a poem.