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Total ozone is defined as the amount of ozone contained in a vertical column with a base area of 1 cm2 at standard pressure and temperature. The units is m atm-cm or DU. For example, a total ozone value of 300 m atm-cm is equivalent to a thickness of 3 mm at standard pressure and temperature.
Total ozone observation is performed dozens of times a day except in rainy and snowy conditions. Daily average data are submitted to the World Meteorological Organization (WMO) as representative values. The WMO Ozone Mapping Centre creates and publishes total ozone maps based on such data. See the Ozone Mapping Centre website for further information.
Total ozone data are also quality-controlled and submitted to the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) for publication on its website.