Targeted Balloon Observations of Stratosphere-To-Troposphere Transport From a Mesoscale Convective System

Stratosphere-troposphere exchange (STE) is important to the global radiation budget because it is capable of inducing significant changes in trace greenhouse gases such as ozone and water vapor. In the extratropics, stratosphere-to-troposphere-or downward-transport (STT) dominates and is routinely driven by upper-troposphere jet circulations and cyclones. Tropopause-overshooting convection provides a more rapid STE pathway, but STT in convection is less understood and targeted observations are limited to a handful of fortuitous aircraft encounters. In this study, we seek to improve understanding of STT near thunderstorm anvils using balloon observations of ozone, ground-based radar observations, visible satellite imagery, and model output. Radar and satellite imagery are used to identify and ultimately target convection driving the "ozone-wrapping" process. Herein, observations from a single mesoscale convective system in central Oklahoma are reported. A significant ozone enhancement 40%-60% greater than background concentrations in the free troposphere was observed during the balloon ascent underneath and within the anvil of the storm. Backwards particle trajectories were calculated to rule out other sources of this feature such as long-range transport of stratospheric air and smoke pollution from nearby wildfires. To our knowledge, this work presents the first targeted ozonesonde launch and sampling of this STT process.