Balloon-based observations of trace gas composition over Europe/Germany in summer 2025, impacted by the Asian Summer Monsoon

For many important trace gases, precise observations in the upper troposphere and lower stratosphere (UTLS) are spatially and/or temporally sparse and/or inhomogeneous. This is particularly problematic since the UTLS features a highly variable transition region between the troposphere and stratosphere. We here present a new dataset obtained from weather balloon-based sensors from the Juelich Modular Balloon Observatory (JUMBO) across the summer and autumn of 2025. Between 27th May and 5th November, 46 balloons were launched on an almost weekly basis from near Jülich, Germany, typically reaching altitudes of around 30 km.  Of those, 37 flights focused on trace gas composition, including 18 near-simultaneous double launches quantifying the vertical distribution of water vapour and ozone as well as multiple halogenated species. The JUMBO campaign was planned, among other objectives, to infer the impact of the Asian summer monsoon on the UTLS over Germany during the full monsoon period. The observations thus enabling access to the temporal evolution of many key UTLS components over a period of about 5 months. Focusing on chlorinated very short-lived substances (Cl-VSLSs) and water vapor in combination with a model-based regional tracer approach, we also investigate the influence of the Asian Summer Monsoon as the respective anticyclone increasingly exports air masses into the global northern hemispheric UTLS.