Monitoring and Management > 4. The Atmosphere >
Analyse the information available that indicates changes in atmospheric ozone concentrations, describe the changes observed and explain how this information was obtained
- Stratospheric ozone is monitored from:
- Ground-based instruments.
- Instruments in satellites.
- Instruments in aircraft.
- Instruments in balloons.
- Ultraviolet spectrophotometer: An instrument that measures the intensity of radiation in the ultraviolet wavelengths.
- Ultraviolet spectrophotometers can be directed vertically upwards through the atmosphere to measure the intensity of ultraviolet radiation of wavelengths that ozone absorbs, as well as the intensity of wavelengths on either side of this range.
- This can provide a measure of the total ozone in the atmosphere per unit area of Earth surface at the location of the spectrometer.
- Ultraviolet spectrophotometers are located around the world and provide total ozone measurements as a function of geographical position.
- Ultraviolet spectrophotometers can also be directed vertically downwards through the atmosphere on craft such as helium balloons.
- Total Ozone Mapping Spectrophotometers (TOMS): Instruments used onboard satellites to scan through the atmosphere and measure ozone concentration as a function of altitude and geographical position.
- TOMSs have been on board several United States satellites over the past 20 years.
- TOMSs can be used to produce ozone profiles and contour maps.
- The depletion of the ozone layer was first observed in the 1970s using ultraviolet spectrophotometry.
- During the 1980s, a combination of the above technologies were used to provide a more accurate view of the changes in atmospheric ozone concentrations.
- TOMs have been especially important since the 1980s in producing maps of the extent of the ozone holes.
- Due to the decrease in the rate of release of CFCs and halons into the atmosphere that has come about through international agreements, a decrease in the rate of ozone depletion has been observed in recent years.
- In 2002, an Australian study announced that levels of ozone-destroying chemicals in the stratosphere were falling and that the ozone hole would begin to start closing in five years, with the process being complete by 2050.
TOMS scan results from 2004