Dobson unit

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Dobson units (DU) are the standard way to express ozone amounts in the atmosphere, specifically the stratosphere. One DU is 2.69 × 10¹⁶ ozone molecules per square centimetre, or 2.69 × 10²⁰ per square meter. One Dobson unit refers to a layer of ozone that would be 10 micrometres thick under standard temperature and pressure. For example, 300 Dobson units of ozone brought down to the surface of the Earth at 0 degrees celsius would occupy a layer only 3 mm thick.

Gordon Dobson was a researcher at the University of Oxford, who, in the 1920s, built the first instrument (now called the Dobson Ozone Spectrophotometer) to measure total ozone from the ground.