The South Georgia Wave Experiment (SG-WEX) - Preliminary Satellite and Modelling Studies

Abstract:

Internal gravity waves, and the energy and momentum they transport, are a key process governing the dynamics and structure of the middle and upper atmosphere, but are significantly underconstrained in current weather and climate models due to their small physical scale relative to typical model grids. In particular, the simulation of such waves is believed to underlie a major momentum deficit in the high-latitude southern hemisphere, due to underestimation of the gravity wave drag provided by waves generated by sub-gridscale island sources.

The South Georgia Wave Experiment (SG-WEX) is a coordinated programme to investigate the most important such small island source, South Georgia Island. This will be carried out via the deployment of a mesospheric-sensing meteor radar, stratospheric satellite measurements, and two month-long tropospheric radiosonde campaigns, backed up by detailed high-resolution modelling of the region at all altitudes. The ultimate goal of the project is to significantly enhance our geophysical understanding of wave dynamics in the region and, more directly, to provide a basis for a dramatic improvement in the parameterisation of the wave momentum flux generated by such small-island sources, with consequent effects on the skill of global weather and climate models both in this region and globally.

Here, we present preliminary results from the satellite and modelling components of the project. In particular, we use combined measurements from the HIRDLS, SABER, AIRS and COSMIC satellite instruments and analyses from the HadGEM GCM to produce a detailed temporal and spatial climatology of wave fluxes in the region, due both to South Georgia and to the nearby Andes and Antarctic Peninsula. We also briefly look ahead to the deployment of the meteor radar and first radiosonde campaign in January 2015, and discuss how these are expected to enhance our understanding of the dynamics of the region.