It means there is less total column ozone than what would read 320DU.
If the level of ozone is below certain concentration, then it is ozone depleted. It is called as ozone hole.
See the "Related questions" section below.
Above: the rest of the stratosphereBelow: the rest of the troposphere
There is not actually a hole in the ozone layer. The ozone has been reduced below some limit.
The stratosphere is the layer that is warmed from below by the ozone layer. Ozone absorbs ultraviolet radiation from the sun, which causes the stratosphere to warm up as the ozone molecules absorb and release this energy. This process creates a temperature inversion where the upper stratosphere is warmer than the lower stratosphere.
If the level of ozone is below certain concentration, then it is ozone depleted. It is called as ozone hole.
The ozone hole is not actually a hole but the lowering of ozone concentration below a certain level. If the concentrations falls below the given concentration. It is referred to as the ozone hole.
See "What does the ozone layer do?" in the "Related questions" section below.
See the "Related questions" section below.
Above: the rest of the stratosphereBelow: the rest of the troposphere
There is not actually a hole in the ozone layer. The ozone has been reduced below some limit.
The stratosphere is the layer that is warmed from below by the ozone layer. Ozone absorbs ultraviolet radiation from the sun, which causes the stratosphere to warm up as the ozone molecules absorb and release this energy. This process creates a temperature inversion where the upper stratosphere is warmer than the lower stratosphere.
Ozone depletion is the thinning of ozone layer below a certain concentration. This phenomenon is termed as ozone depletion.
See "How can ozone be harmful and helpful?" in the "Related questions" section below.
See "What does the ozone layer do?" in the "Related questions" section below.
See "What can we do to protect the ozone layer?" in the "Related questions" section below.
See "What does the ozone layer do?" in the "Related questions" section below.