Monitoring ozone levels
Dr Greg Bodeker was a research scientist for the National Institute of Water and Atmospheric Research (NIWA), based at Lauder in Central Otago. Lauder is the primary southern hemisphere mid-latitude site in the Network for the Detection of Atmospheric Composition Change (NDACC), and Greg collaborated with other scientists around the world in this network to monitor the amount of ozone in the atmosphere, mainly where ozone has greatest concentration in the ‘ozone layer’ between 15 and 30 kilometres above the Earth’s surface. This is important work because ozone absorbs most of the UV radiation from the Sun and so protects the Earth from too much UV.
One way the Lauder scientists measure ozone concentrations is through weekly launches of an ozonesonde attached to a hydrogen-filled weather balloon. As it rises, the ozonesonde takes regular samples of air, mixes the samples with chemicals to determine the ozone concentration, and radios the measurement back to Lauder along with measurements of altitude, temperature, humidity and air pressure. This way, a vertical profile of ozone concentration is obtained.
Ozonesonde launch
The weekly launch of an ozonesonde at Lauder in Central Otago enables scientists to monitor the distribution of ozone up through the atmosphere.
The researchers at Lauder also use a ground-based instrument – the Dobson spectrophotometer – to measure the total amount of ozone above Lauder. The spectrophotometer measures and compares the UV light intensity at wavelengths that are strongly absorbed and weakly absorbed by ozone. The column ozone content of the atmosphere is calculated from the ratios of these intensities.
Dobson spectrophotometer
The Dobson spectrophotometer at Lauder in Central Otago is a key ozone-measuring instrument used by NIWA and is part of a global network of similar instruments.
Greg’s research centred on trying to find a better understanding of the links between ozone depletion and climate change and to improve computer models of those links so that more accurate predictions can be made, so he and other colleagues around the world can advise politicians in the implementation of international policies. Linked with this, Greg and his colleagues have found a definite increase in atmospheric ozone levels since the 1989 Montreal Protocol, where countries started to phase out emissions of ozone-depleting substances such as chlorofluorocarbons (CFCs) used in spray cans.
Studies by Greg and his colleagues have shown a two-way link between ozone and climate change. Using a very complex ‘coupled chemistry-climate model’ developed by the United Kingdom Metrological Office and running on NIWA’s supercomputer, Kupe, they have shown that increases in greenhouse gases in the atmosphere will actually speed the recovery of the ozone layer, at least over New Zealand. On the other hand, the Antarctic ozone hole has played a key role in the surface climate in Antarctica. It has caused the interior of the Antarctic continent to warm more slowly than it would otherwise.
Nature of science
Where appropriate, scientists construct mathematical computer models of systems they are studying so that they can understand the relationships within the system and predict future trends. New measurements of the real systems enable the computer models to be fine-tuned to make them more accurate.
Greg and Hamish Struthers at Lauder also collaborated with 21 other scientists world-wide to extend their coupled chemistry-climate computer model to simulate the effect of the Sun’s 11-year cycle on ozone and temperature in the Earth’s atmosphere. Their results agree with actual satellite observations but are in contrast with most previously published simulations.
Related content
In this video, Greg answers the question: “What key ideas would you want school students to understand about your research?”
Find out more about NIWA’s research programme in measuring the variability of natural UV radiation in New Zealand, to understand the causes of its variability and to monitor long-term trends.
Dr Adrian McDonald from the University of Canterbury relies on satellites to study the atmosphere over Antarctica. His research focuses on factors that affect the Antarctic climate, the ozone hole and their interactions.
Researchers are also now able to measure methane from space using satellites.
Scientists use modelling to help make predictions, below are two other examples:
Useful links
NASA's Eyes on the Earth site shows the positions of their Earth observation satellites. Use the tabs at the bottom of the page to filter for greenhouse gases and other measurements.
In 2010 Greg set up his own atmospheric research company, Bodeker Scientific, specialising in the science of stratospheric ozone depletion, stratospheric composition and climate change.
See the Network for the Detection of Atmospheric Composition Change website.
