Bacteria, plants and even lightning can all play a role in the pleasant smell we experience after a thunderstorm; that of clean air and wet earth. What you’re smelling is actually a molecule being made by a certain type of bacteria. Drops of water hitting the ground cause geosmin, an organic compound, to be released into the air, making it much more abundant after a rain shower.
Now, geosmin is becoming a common perfume ingredient. Perfumer Marina Barcenilla says, “It’s a really potent material and it smells just like the concrete when the rain hits it. There’s something very primitive and very primal about the smell. Even when you dilute it down to the parts per billion range, [humans] can still detect it.” she added.
Thunderstorms have their role to play too, creating the clean, sharp scent of ozone – caused by lightning and other electrical discharges in the atmosphere. For more insight, the BBC has a detailed article on the topic. Click this link to read more: https://www.bbc.co.uk/news/science
Image source: Steve Boyton