Which of the following is measured in Dobson Units?

Dobson units measure the total column amount of ozone in the stratosphere overhead.

Chlorofluorocarbons are measured by concentration in parts per trillion, not Dobson units.

Ultraviolet rays are measured by intensity or the ultraviolet index, not this unit.

Solar radiation is measured in watts per square metre, not Dobson units.

One Dobson unit equals a layer of pure ozone about 0.01 millimetre thick at standard conditions.

The Antarctic ozone hole is defined by column values dropping below 220 Dobson units.