Typical ozone column values Total ozone column value ranges from 290 to 310 DU over the globe. If all the atmosphere' s ozone were brought down to the earth's surface at standard pressure and temperature, it would produce a layer of about 3mm thick Ozone depletion: when sum of ozone over height is lower than 2/3 of the normal value we say"ozone depletion " occursTypical ozone column values • Total ozone column value ranges from 290 to 310 DU over the globe. • If all the atmosphere's ozone were brought down to the earth's surface at standard pressure and temperature, it would produce a layer of about 3mm thick. • Ozone depletion: when sum of ozone over height is lower than 2/3 of the normal value, we say "ozone depletion" occurs