Petrichor

After it rains in LA, the air is so clear and it has a delicious fresh scent. 
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Some plants secrete oils during dry periods, and when it rains, these oils are released into the air. Also chemicals produced by soil-dwelling bacteria are released. Another scent associated with rain is ozone.  These aromatic compounds combine to create the pleasant "petrichor" scent when rain hits the ground. In LA, the biggest contributor is that the rain clears the smog and pollution. Anyway, today the air is noticeably beautiful.