MEASUREMENT/UNIT

Ozone layer thickness is expressed in terms of Dobson units which is measure what is physical thickness would be if compressed in earth atmosphere. 1 Dobson unit is defined to be 0.01 mm thickness at STP (standard temperature and pressure) . The unit is named after G.M.B Dobson , one of the first scientist to investigate atmospheric ozone. 1 Dobson is equal to 2.687×10²⁰  molecules of ozone per square metre.

The Dobson unit (DU) measures the column density of ozone in the Earth's atmosphere. Column density refers to the total number of ozone molecules in a vertical column of air extending from the ground to the top of the atmosphere. One Dobson unit represents a layer of pure ozone 0.01 millimeters thick at standard temperature and pressure.