SAOZ

SAOZ measures sunlight scattered from the overhead sky in a way that allows us to calculate how much of the atmospheric gases ozone and nitrogen dioxide the light has passed through on its journey.

Monitoring ozone is vital if we want to know what is happening to the Antarctic ozone hole. Nitrogen dioxide is also useful because changes in levels of this gas show how gases are circulating between different levels of the atmosphere. This vertical circulation of gas is what takes CFCs emitted at the surface up to the ozone layer 20km above us, where they are broken down to release chlorine, which destroys ozone. We can also track the passage of greenhouse gases up to levels where they have an even stronger effect on climate than those that stay nearer the surface.

Computer models have predicted that as the climate changes over the next century, the vertical circulation pushing greenhouse gases and CFCs upwards will get stronger (bad news as it means more ozone destruction and stronger greenhouse warming!) We need the SAOZ measurements to find out whether the predictions are coming true.

SAOZ has been the roof of the Science Module since 2012. Its automatic ozone measurements are compared with those from the manually operated Dobson, which has been running at Halley since the beginning of time. One day, SAOZ may become the main instrument used for measuring ozone at Halley.