What is petrichor? Meaning of the word explained - where does smell of rain after dry weather spell come from

The smell of rain after a long draught has a very distinctive scent

The UK has seen one of its warmest ever summers, with temperatures soaring up to 41C in July 2022 beating the temperature records which had been previously recorded in 1976.

During the heatwave the UK has witnessed its driest July since 1935, with a number of water companies imposing hosepipe bans in order to save supply.

With much needed rain reaching parts of the UK, many people such as farmers and gardeners throughout the country will have benefited from the outbreak of rain.

Many people throughout the country have also been questioning the strange smell in the air, following the first rain after a long dry spell.

The scent is known as petrichor and it has been studied by a number of researchers and scientists.

Areas of the UK were declared to be in drought during 2022 (Getty Images)Areas of the UK were declared to be in drought during 2022 (Getty Images)
Areas of the UK were declared to be in drought during 2022 (Getty Images)

What is petrichor?

Petrichor is a term used to describe the smell that accompanies rain when it lands on dry ground.

The term was first used by Australian researchers Isabel Joy Bear and Richard in the 1964 journal ‘Nature’.

What does ‘Blood of the Rocks’ mean?

The word petrichor is derived from two Greek words. In Greek mythology gods and immortals didn’t have blood flowing through their veins; they were animated by ichor. Since petra means stones, petrichor is the blood of a stone which can be released through light rainfall.

Where does the smell come from after it rains?

During dry conditions plants release different types of oils and when the rain hits the plants these oils are released into the air.

Just before a rain event, after a sustained period of dryness, the air becomes more humid and the ground becomes moist, forming a molecule known as geosmin.

When drops of water hit the ground, they form tiny air bubbles when they hit the soil. These bubbles build up and burst into the air to release the scent similar to a glass of champagne.

Petrichor is essentially a combination of geosmin and the oils that are released into the air and the combination creates a long lasting smell.

The human nose is extremely sensitive towards geosmin and is able to detect it at a concentration of five parts per trillion.

Many scientists believe the smell is popular as cultures throughout history have been heavily reliant on rain. The scent is so potent that it has been recreated in perfumes and candles.

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