Ozone is created in the middle to upper stratosphere of the tropics. It is here that the Sun provides enough of the necessary extreme ultraviolet (EUV) light. The EUV breaks down diatomic oxygen molecules, O2, into free oxygen atoms, which then recombine with other oxygen molecules to form ozone, O3. As we have seen from its vertical profiles at different latitudes, ozone has an elevated peak somewhere in the lower to mid stratosphere, roughly 20 to 40 km in altitude. It is at these altitudes where the creation of ozone is maximized owing to two effects: a sufficient supply of oxygen and a sufficient amount of incoming UV light. Above and below these heights, these two effects work against each other. An additional characteristic of ozone arising from its vertical distribution and the amount of penetrating UV light involves the length of time an ozone molecule exists between its creation and destruction. Both processes involve UV light. The so-called "lifetime" of an existing ozone molecule residing at some level is determined by how long it takes a UV photon to penetrate into the atmosphere to that level and to break apart the molecule in a process known as photolysis.
Ozone is created when extreme ultraviolet light (EUV) breaks apart oxygen molecules high up in the atmosphere. Ozone is destroyed when UV light breaks apart the ozone molecules. Both processes involve UV light. The so-called "lifetime" of an existing ozone molecule residing at some level is determined by how long it takes a UV photon to penetrate into the atmosphere to that level and to break apart the molecule in a process known as photolysis.
Ozone molecules existing below the ozone peak can "live" for weeks to months without being destroyed by a stray UV photon. This is because the layer of ozone molecules above it are absorbing most of the UV photons. In the process of destroying (photolyzing) an ozone molecule, a photon loses enough energy that it is no longer biologically harmful UV radiation. This is precisely how the ozone layer shields Earth. The lower into the atmosphere you go, the longer an ozone molecule lives with lifetimes for molecules below the peak layer on the order of weeks to months.