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Dobson Unit measures which part of the atmosphere?
The
Dobson Unit (DU) is the most common unit for measuring ozone concentration.
The Dobson spectrophotometer measures the total amount of ozone in a column extending from Earth's surface to the edge of space in
Dobson Units, defined as the number of ozone molecules that would be required to create a layer of pure ozone 0.01 millimeters thick at a temperature of 32 degrees Fahrenheit at an atmospheric pressure equivalent to Earth's surface.
Satellite- and balloon-borne instruments showed that the amount of ozone over Antarctica bottomed out in early October at a value of 90 to 92
Dobson units, the same as last year.
Measurements with balloon-borne instruments launched by NOAA personnel at the South Pole in early October 1988 show that the amount of ozone in an air column above the site averaged more than 200
Dobson units, according to Walter Komhyr of the Commerce Department agency's Environmental Research Laboratories in Boulder, Colo.
"There was about half as much ozone loss as in the Antarctic and the ozone levels remained well above 220
Dobson units, which is the threshold for calling the ozone loss a 'hole' in the Antarctic - so the Arctic ozone loss of 2011 didn't constitute an ozone hole," Strahan said.
The satellite also showed that ozone concentrations in the worst section of the hole bottomed out at 90
Dobson units, only one-third of what should normally be there this time of year.
Total ozone, measured in
Dobson units (DU), reached 124 DU on Oct.