The Ozone Hole
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August 2001 

NASA Earth Probe TOMS  Images

Ozone Measurement

1 Dobson Unit (DU) is defined to be 0.01 mm thickness at STP (standard temperature and pressure). Ozone layer thickness is expressed in terms of Dobson units, which measure what its physical thickness would be if compressed in the Earth's atmosphere.

The white area on the images is where data cannot be retrieved in the earth's shadow or polar night regions by the satellite.