Characteristics of Lower Stratospheric Gravity Waves Observed During the Perlan Project Mission II Expedition

The Perlan II glider soars in stratospheric gravity waves, setting subsonic aircraft altitude records while collecting atmospheric data to advance aeronautical and meteorological knowledge. During the Perlan Mission II in Austral winter of 2018 and 2019, radiosonde and aircraft data were collected from El Calafate, Argentina (-50.28°, -72.05°) in the lee of the Southern Andes near the Southern Hemisphere polar night jet. This is a known hot spot for gravity wave activity, however, direct atmospheric observations are sparse resulting in poor atmospheric and climate model performance. Gravity waves can deposit energy and momentum far from their source and are not fully resolved in numerical models. This phenomena must be properly parameterized based on physical observations to depict atmospheric conditions more accurately. During the 2019 campaign, a rare Southern Hemisphere sudden stratospheric warming occurred. Data collected during the Perlan Mission II, via radiosonde and the suite of instruments on board the Perlan II glider, is used to determine the characteristics of gravity waves observed in the lower stratosphere which are initiated in the region from tropospheric or stratospheric sources. Gravity waves are characterized by their vertical and horizontal propagation properties, energy density, and momentum flux. The results suggest that, in addition to the typical mountain waves propagating upward into the stratosphere, there is an increased presence of downward propagating waves with a stratospheric source observed during the sudden stratospheric warming.