Trace gas balloon borne in situ measurements in the Southern Hemisphere

The Southern Hemisphere has long been underrepresented in high altitude in situ trace gas measurements. This leads to significant uncertainties in understanding and predicting their effects on stratospheric chemistry and circulation. In a pioneering effort, a balloon campaign took place in Beaufort West (32.3540 ˚S, 22.5833˚E) in early 2023, the first of its kind in South Africa. Two different sensor packages were launched during six balloon flights and reached altitudes up to 33 km. These balloon flights provided unique measurements of key atmospheric constituents, including water vapor, ozone, CO2, CH4, CO, SF6, and various ozone depleting substances.

Here, we present an overview of these findings, along with a comparison with similar data from the Northern Hemisphere, and with data from the Chemical Lagrangian Model of the Stratosphere (CLaMS). A first notable result revealed the sampling of tropical air masses with unusually low water vapor mixing ratios [2.1 ppmv] around the upper troposphere and lower stratosphere (UTLS) region. A follow-up campaign is planned for 2024 to further enrich the dataset and enhance insights into stratosphere-troposphere exchange dynamics.