Impacts Of Tropopause Structure On Deep Convective Transport: Results From Modeling And Observations (INVITED)

Deep convection, such as severe thunderstorms observed throughout the United States in spring and summer, is an efficient transporter of gases, both anthropogenic and natural, from the boundary layer to the upper-troposphere/lower-stratosphere (UTLS). Troposphere to stratosphere exchange is uncertain in observations of active deep convection because the highly perturbed state of the tropopause makes quantifying irreversible transport difficult. In addition, recent studies indicate that the unperturbed structure of the tropopause, e.g. single versus double tropopause or weak versus strong inversion, also has a measurable impact on the magnitude of deep convective transport. Findings on the impacts of tropopause variability on transport from two different ongoing projects will be the focus of this presentation.

A three-dimensional cloud-resolving model is used to simulate the transport of boundary layer tracers into the lower stratosphere via midlatitude supercells. We analyze three cases: a single tropopause, a weak inversion double tropopause, and a strong inversion double tropopause. Preliminary results show differences in mass aloft during the mature stage of the storm, but only minor differences in irreversible transport. Further, chemical plumes and tropopause structures are investigated using aircraft observations from both the NASA MACPEX and SEAC4RS missions. Enhanced carbon monoxide plumes are identified from in situ vertical profiles, and back trajectories and observations of precipitation are used to verify which parcels were influenced by recent convection. The tropopause structure in the vicinity of each plume is then categorized using aircraft data. Preliminary results show the majority of analyzed plumes show double tropopause structures, but only double tropopause structures with weak inversions show increases in plume penetration depth.