A2-Dglobalchemistry-transportmodelissetupinthispaper.Themodelsimulatestheatmosphericozonedistributionswellwithspecifieddynamicalconditions.Theanalysisofozonevariationmechanismshowsthatozoneischemicallyinquasi-equilibriumexceptforthepolarnightregionwherethevariationofozoneconcentrationisunderthecontrolofdynamicalprocesses,thattheoxygenatomswhichproduceozonearemainlyprovidedbythephotolysisofO2intheupperstratosphereandbythephotolysisofNO2inthelowerstratosphereandthetroposphere.andthattheozoneisdestroyedmainlybyNOx:thereactionsbetweenNOxandO3andtheoddoxygencyclecontribute80%tomorethan90%oftheozonedestruction.