How are ozone levels measured?
Australia takes part in the Global Atmosphere Watch (GAW) international monitoring and research program coordinated by the World Meteorological Organization (WMO). The Bureau operates a network of ozone monitoring stations (at Melbourne, Brisbane, Darwin, and Macquarie Island), where the total amount of ozone above the station (total column ozone) is measured several times every day. The total column ozone is measured with an instrument called a Dobson spectrophotometer, which compares the amount of sunlight at two ultraviolet wavelengths, one wavelength being strongly affected by ozone and the other one not. Total column ozone can then be calculated from the difference in the sunlight measured at the two wavelengths. The Bureau also flies ozonesondes weekly from Macquarie Island and Melbourne (using the Bureaus training annexe at Broadmeadows), as well as a partial program at Davis in Antarctica funded in part by the Australian Antarctic Division. Ozonesondes are devices which measure
