Middle Frequency Radar Measurements: Dynamics and Ionisation in the Antarctic Middle Atmosphere from Scott Base

Our studies investigate the Antarctic middle atmosphere’s response to natural and man-made factors which change climate. The dynamical processes of this region are significant in controlling the circulation at lower altitudes, including the stratospheric ozone layer. The feedbacks in the atmosphere, couple this change to climate change at the surface. The seasonal behaviour of this wave-driven circulation, particularly its dependence on major disturbances in the stratosphere which result in the transport of energy and momentum by waves to higher altitudes are examined. The programme is based on continuous monitoring of winds in the middle atmosphere at altitudes of 60-100km using a ground-based medium frequency radar located at Scott Base. The Scott Base radar has been recording wind measurements since 1982 and is one of the longest duration climate records of this type of data in the world. The measurements made by the Scott Base MF radar provide valuable climate information about how the flow in the middle atmosphere (70-100 km) has changed. This record along with observations from satellite instruments allows the coupling between the middle atmosphere and the surface over Antarctica to be examined, this coupling is often associated with wave-like motions in the atmosphere that the MF radar is particularly good at observing. The circulation is dominated by pole-to-pole flow, from the summer pole to the winter pole. This circulation is largely driven by atmospheric waves with time scales from 15 minutes to 15 days. The large scale of the phenomenon benefits considerably from co-operative observations by our own radar near Christchurch, and by our US colleagues at the South Pole, Admiral Heights (from January 2000) and Tekapo. We also use satellite data for the region between Antarctica and New Zealand. This type of study is important because improvements in the predictive ability of the current generation of climate models may be particularly sensitive to the coupling processes that we examine.