<Table> <Tr> <Td> </Td> <Td> This section needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2013) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This section needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2013) (Learn how and when to remove this template message) </Td> </Tr> <P> The thickness of the ozone layer--that is, the total amount of ozone in a column overhead--varies by a large factor worldwide, being in general smaller near the equator and larger towards the poles . It also varies with season, being in general thickest during the autumn and thinner during the early spring . The reasons for this latitude and seasonal dependence are complicated, which involve in atmospheric circulation patterns as well as solar intensity . But in general, bitterly cold temperatures mixed with sunlight assist in maximum ozone depletion, which occurs in early spring . </P> <P> Since stratospheric ozone is produced by solar UV radiation, one might expect to find the highest ozone levels over the tropics and the lowest over polar regions . The same argument would lead one to expect the highest ozone levels in the summer and the lowest in the winter . The observed behavior is very different: most of the ozone is found in the mid-to - high latitudes of the northern and southern hemispheres, and the highest levels are found in the spring, not summer, and the lowest in the autumn, not winter in the northern hemisphere . During winter, the ozone layer actually increases in depth . This puzzle is explained by the prevailing stratospheric wind patterns, known as the Brewer - Dobson circulation . While most of the ozone is indeed created over the tropics, the stratospheric circulation then transports it poleward and downward to the lower stratosphere of the high latitudes . However, owing to the ozone hole phenomenon, the lowest amounts of column ozone found anywhere in the world are over the Antarctic in the southern spring period of September and October and to a lesser extent over the Arctic in the northern spring period of March, April, and May . </P>

The thickness of the ozone layer in the atmosphere varies by
find me the text answering this question