1. "-" indicates no data; "**" indicates annual average is not calculated due to some monthly data missing.
2. Total ozone is represented with a special unit of measurement. If all the ozone in a column over an area was to be compressed and spread out evenly, it would form an ozone layer. The thickness of ozone layer measured under standard temperature and pressure with 0.001cm is defined to be 1 Dobson Unit (DU).