Like the fresh smell of rain after a storm? It could be petrichor. Petrichor (peh-trih-kor) is defined as “the earthy scent produced when rain falls on dry soil.” I notice the scent even as the rain falls on dry pavement, probably because the pavement is usually dusted with a fine layer of soil.
The image below comes from a Science News article, published online on 10 Feb. 2015 and in print on 4 Apr. 2015, p. 5, under the topic “Mystery Solved.” It discusses original research by MIT mechanical engineers Cullen Buie and Youngsoo Joung. The research is published in Nature Communications, which is not open access, but you can read the abstract and the references. There’s even a video from MIT you can watch that helps explain the research. Basically, raindrops produce tiny, fizzy bubbles that pop (kind of like soda bubbles when you open a fresh can [the header to this blog is a closeup shot of soda bubbles]), releasing the classic petrichor sent.
LiveScience published a story on 21 June 2013 about the scent of rain that discusses petrichor and another scent, called ozone, that is carried in by the rain. Ozone (which has many other definitions) can be sensed even before a rainstorm and may be caused by lightning, according to the LiveScience article. We here in Colorado get a lot of that scent in the summer during our daily afternoon thunderstorms. It’s almost intoxicating and always welcome.