How is total ozone distributed over the globe? By Ginny Bister, Robert Metcalfe, Ivan Mariscal

Total ozone Is defined as the sum of all ozone in the atmosphere directly above a certain location Most ozone resides in he stratospheric ozone layer and only about 10% is distributive throughout the troposphere Measured in Dobson Units (DU) Typical values are between 200 and 500 DU 500 DU could form a layer of pure ozone gas at the earths surface with a thickness of 5 millimeters

Global distribution Total ozone varies strongly with latitude Largest values occurring at middle and high latitudes This is result of ozone production rates from solar ultra-violet radiation Total ozone values are lowest in the tropics

Seasonal distribution Total ozone varies with season March and September plots represent the early spring and fall seasons in the northern and southern hemispheres June and December plots represent the winter and early summer seasons Total ozone shows a maximum high latitude during spring because of increased ozone transport Ozone transport is weaker during summer and early fall

Seasonal distribution cont. In the Antarctic, a pronounced minimum in total ozone is observed during the spring. The minimum is a consequence of an “ozone hole”, which describes the widespread chemical destruction of ozone by ozone depleting substances in spring Now, the lowest values of total ozone in all seasons are found every spring in the Antarctic

Early spring Early fall Early summer Early winter Early fall Early summer Early winter Early spring

Natural variations Patterns change on daily to weekly timescales Natural air motions blend air between regions of the stratosphere that have high ozone values and those that have low ozone values Changes in balance of chemical production and loss processes as air moves to and from different locations This balance is very sensitive to the amount of sunlight in a region