Convective local tropopause modifications and entrance into the stratosphere - a modelling perspective

Convection represents a major pathway of moisture and trace species into the upper troposphere. However, the role of convection for cross-tropopause transport is still under discussion, e.g., the processes of moisture entry into the lower stratosphere. Deep convection highly perturbs the local tropopause structure, which is partly reversible. It thus can either penetrate the tropopause, injecting trace species (including water) into the stratosphere, but it can also lead to a lifting of the tropopause as the thermals from below and their adiabatic cooling reach to higher altitude.

In this study, we analyse model results on the kilometer scale of idealised deep convective events and analyse the modifications of the tropopause above convection, using both thermal as well as dynamical tropopause definitions. Furthermore, we depict how the thermal structure of the atmosphere is modified after the convective event, effectively changing the tropopause altitude. Additionally, we determine the amount of water vapour transported to elevated altitudes above the original tropopause and how much water irreversibly enters the stratosphere. The exchange also encompasses downward transport of air masses with stratospheric characteristics into the troposphere. We analyse, which factors (e.g., vertical wind shear, CAPE and the strength of the initial disturbance) show the strongest influence on the tropopause modifications and, therefore, assess the effects of deep convection for the UTLS.