Discovery of record-breaking mountain waves above the South American Andes

Mountain waves are generated by strong wind that crosses mountains. The energetic waves propagate high up into the atmosphere where they can break similar to ocean waves. We know from satellite observations that the strongest mountain waves in Earth’s atmosphere occur above the southern Andes in South America. For this reason, the CORAL lidar of the institute’s Middle Atmosphere-matrix group was brought to Rio Grande in southern Argentina. Using CORAL we are able to observe these waves at high resolution, every night and up to 90 km altitude. Already during the first winter, in July 2018, we observed stronger mountain waves than ever known: with vertical wavelengths of 16 km, peak-to-peak temperature amplitudes of 80 K, and for a duration of several days. Comparisons with model analyses of the European Centre for Medium Range Weather Forecasts (ECMWF) confirmed the measured quantities very accurately. Using the model, we deduce how the mountain waves propagate within the edge of the polar vortex and influence the larger-scale circulation for several thousand kilometers downstream. These results were now accepted for publication in the Nature journal Scientific Reports.