Abstract

Gravity waves are an important type of atmospheric wave. They play a key role in many atmospheric processes, ranging from convection to the mixing of chemical species to influencing the global-scale circulation of the stratosphere and mesosphere. Because of this, it is essential to represent their effects in numerical weather prediction and climate models.

Gravity waves are generated by sources including winds blowing over mountains, jet-stream instabilities and strong convection. The waves can transport energy and momentum away from these sources and deposit them at greater heights, thus exerting a significant “drag” on the circulation and so coupling together different layers of the atmosphere.

Recent studies have shown that isolated mountainous islands in regions of strong winds can be intense sources of gravity waves that can have climatologically-significant effects on atmospheric circulation. However, most climate and numerical weather prediction models cannot accurately model waves from such small, intense island sources because the islands are too small compared to the resolution of the models – this is the “small island problem”.

The South Georgia Gravity Wave Experiment (SG-WEX) is a NERC funded observational and modelling experiment to determine the nature and impacts of gravity waves generated by South Georgia (a small, mountainous island in the Southern Ocean). It is a collaboration between Bath University, BAS , Leeds University and the Met Office.

Earlier this year two month-long radiosonde campaigns were conducted from South Georgia to examine the gravity wave field in the troposphere and lower stratosphere. The results from these two campaigns are presented in this talk alongside preliminary satellite and model results.