The goal of this project is to greatly improve the capabilities of the Medium Frequency (MF) radar system at Arrival Heights, Antarctica. The upgrades will allow studies of gravity waves in the Antarctic middle atmosphere at this latitude for the first time. These waves are the determining factor in controlling the flow in the middle atmosphere. General circulation models use parameterizations of these waves to make realistic predictions. However, these parameterizations are severely limited by the lack of knowledge about these small-scale features and thus greater understanding of these waves is of tantamount importance in improving the predictive ability of general circulation models in this region. Being able to make measurements of the gravity waves and their interactions with modern high time resolution instruments like the proposed system, is vital for improved understanding and future models. This is especially true for high latitudes where there are very few studies (Fritts and Alexander, 2003).

This study will also allow the long-term monitoring of the Middle atmosphere with the MF radar to continue unabated. This long-term monitoring function is particularly important because the Antarctic radar system has been in operation since late 1982 and the 22 year record makes up the longest duration climate record of this type of data in the World. The results of simulations have suggested that the dynamics observed by these radar systems may be particularly sensitive to climatic variations. For example, simulations indicated that variations in CO₂ and CH₄ will cause mesosphere and lower thermosphere temperatures to cool by about 10K and 50K, respectively. A more recent study, by Khosravi et al. (2002), indicates that the impact of doubling the CO₂ abundance cools the winter polar mesosphere by 16K. These values are as significant or larger than the predicted effects at the surface and thereby suggest that the mesosphere may be a particularly important region to monitor for signs of anthropogenic climate change. However, observations in the mesosphere may be complicated by other long-term variations, such as the Solar cycle, El-Nino Southern Oscillation and the Quasi-Biennial Oscillation. Thus, studies indicating changes in the mesosphere associated with climate change are highly controversial because many studies have been inconclusive at best. The quality and extent of this dataset means that it has become highly important to the middle atmosphere community.

REFERENCE:

A. J. G. Baumgaertner, M. J. Jarvis, A. J. McDonald and G. J. Fraser, 2006, Observations of the wavenumber 1 and 2 components of the semi-diurnal tide overAntarctica, Journal of Atmospheric and Solar-Terrestrial Physics(in press).

A. J. G. Baumgaertner, A.J. McDonald, G.J. Fraser and G.E. Plank, 2005, Long-term observations of mean winds and tides in the upper mesosphere and lower thermosphere above Scott Base, Antarctica, Journal of Atmospheric and Solar-Terrestrial Physics, 67, 1480-1496.