The net result between ozone formation and ozone destruction is the steady-state concentration. If the steady-state is disturbed so that more is destroyed than produced, then there is a depletion in the ozone concentration. In the lower stratosphere and upper troposphere and in the upper stratosphere and thermosphere, ozone concentrations are lower. The concentration of ozone varies with latitude and season. Stratospheric winds transport ozone from tropical regions to the poles.
Solar radiation varies with seasons as well.
It should merely be referred to as a depletion of ozone below steady-state concentrations. Ozone depletion is probably caused by reactions with other air pollutants that rise above the troposphere. X. An example of X is atomic oxygen O, that is found in the upper stratosphere. N2O rises from the troposphere, hits an atom of oxygen from photochemical decomposition of ozone, and sometimes NO is formed. Then NO destroys ozone.