The total amount of ozone in an atmospheric column at a given location is measured in Dobson Units (DU), named after Dobson who developed methods of measuring atmospheric ozone from the ground. Dobson units represent how thick a layer of ozone from the surface to the top of the atmosphere would be if it all existed at 0C and the average surface pressure. 300 Dobson Units is 0.3 cm thick or approximately the thickness of a dime.
Average total ozone amounts as a function of month (x-axis) and latitude (y-axis).
Column ozone amounts range from less than 240 DU to more than 450 DU. On average, the minimum amount of the latitudinal average total ozone occurs in the tropics. Most ozone is produced in the tropics, yet the greatest column amounts are found in the midlatitudes and polar regions. Winds in the stratosphere transport ozone and explain the higher concentrations outside the tropics. The winds carry ozone produced in the tropics towards the poles, lowering tropical concentrations while raising the ozone levels in the midlatitude and polar regions.
The vertical distribution of ozone is also a function of latitude.
