Dobson unit

A Dobson Unit (DU) is a measure of the amount of ozone in a column of the Earth's atmosphere. It is defined as the number of ozone molecules in a column of air that is 1 square centimeter in cross-section and extends from the surface of the Earth to the top of the atmosphere, weighted to a standard pressure and temperature. Specifically, 1 Dobson Unit corresponds to a total column of ozone that would create a layer of pure ozone 0.