Monthly means of total column ozone over Macquarie Island

Measurement Technique: Global-scale daily analyses are produced by the Bureau of Meteorology on a 2.5 - degree latitude by 2.5 - degree longitude grid, using satellite data. In situ Dobson spectrophotometer measurements at Macquarie Island in conjunction with major centres in Australia provide benchmark and calibration data of total-column ozone. Macquarie Island is the only station situated under the Antarctic Ozone hole, providing an important contribution to ozone monitoring activities.

RESEARCH ISSUES The traceable data set may be extended back a few years before 1978 but cannot go much further back with any confidence. When Dobson measurements began seriously in 1955, there was no traceability of instrument standards. Each instrument was calibrated absolutely rather than by the hierarchy of standards, beginning in 1978.

In the initial measurement program, ozone measurements were used mainly for day-to-day variations - the idea of using Dobsons for a long-term trend in ozone was not an objective. Consequently the need for properly referenced instruments was not a high priority. The difficult mechanism of applying standards was not in place when measurements started in 1956.

LINKS TO OTHER INDICATORS SOE Indicator 10 - Daily broad-band ultra-violet radiation observations using biologically effective UVR detectors SOE Indicator 13 - Polar stratospheric cloud observations at Davis