Ozone amounts can be expressed in molecules per cc, parts per million (ppm), or Dobson units.   Units of ppm are normally used to express the concentration at a specific point.  A measurement of 8 ppm means that if you randomly take a million air molecules, 8 of them will be ozone.  Dobson unit are used to express the amount of ozone in a vertical column between say the surface and the very top of the atmosphere.  100 Dobson units means that if you take all the ozone in the atmosphere above a certain point and squeeze it down to sea level pressure and 0 degrees Celsius then it would be a layer 1.0 mm thick (1.0 mm= 0.001 meters).

TOMS:  Total ozone mapping Spectrometer.  Approximates the total ozone column by measuring and comparing different wavelengths of sunlight.   Different TOMS instruments have been carried on different satellites since Nov 1978.  The sun must be shining for TOMS to work.  Thus no data is collected at high latitudes in the winter months.

Ozone Sonde and Aircraft.  An instrument that is typically deployed with a balloon and radio transmits data back to a base camp.  Measures concentrations (ppm) at specific vertical levels in the atmosphere.  This data can then be used to calculate total ozone column amounts (Dobson Units).  Aircraft equipped with sophisticated instruments are also used to measure ozone concentrations and other key atmospheric parameters at specific locations.

UARS  The Upper Atmosphere Research Satellite.  Launched in 1991.  Instruments look at the atmosphere edge on so, like a sonde, UARS can estimate concentrations at specific heights as well as total column amounts.  The ability to distinguish one vertical level from the next is limited with satellite measurements so when good vertical resolution is needed Ozone sondes or instruments aboard aircrafts are used.

Home