Investigation of the gravity wave hotspot above Tierra del Fuego utilizing an autonomous Rayleigh lidar system

The southern tip of South America is known to be one of the largest global hotspots of atmospheric gravity waves. Understanding the excitation, propagation and dissipation of waves at this key location may shed light on the missing gravity wave drag in contemporary climate chemistry models at 60° south and may provide approaches to solving the cold pole problem. Observations of gravity waves in the middle atmosphere above southern Patagonia were mostly done utilizing space-borne instruments with rather coarse resolution in space and time. In order to investigate the thermal structure of the middle atmosphere at this extraordinary location in high resolution we installed the Compact Rayleigh Autonomous Lidar (CORAL) in Río Grande (54°S, 68°W) in November 2017. Since then we obtain temperature profiles from 15 - 90 km altitude with temporal resolutions down to 10 minutes at night whenever weather conditions allow for it. The data coverage with on average four measurements per week throughout the years is excellent in comparison to other lidar studies and enabled robust statistical analysis of gravity wave properties. In the southern hemisphere (SH) winter the temperature measurements show strong mountain wave signatures with peak-to-peak amplitudes of up to 80 K. In order to quantify the gravity wave activity we determined monthly averages of the gravity wave potential energy density (GWPED). We identified conservative growth rates in the winter upper stratosphere and summer mesosphere lower thermosphere (MLT). SH winter month GWPED profiles reveal growing wave amplitudes up to 60 km altitude. Above, in the mesosphere and MLT region energy densities reach a constant limit in that period. Furthermore, we determined a vertical wavelength spectrum focusing on dominant modes based on wavelet analysis and a clustering algorithm. We found two distinguishable wave populations in the spectrum. The major one exhibits vertical wavelengths decreasing from 18 to 11 km in the altitude range 20 - 70 km. The smaller one is only perceivable at 40 km altitude and features vertical wavelengths of 23 km.