Penetrative convection

From Glossary of Meteorology

penetrative convection

The result of buoyant thermals that encounter a capping stable layer and have sufficient energy to travel some distance into the stable layer.

This penetration may lead to mixing of fluid between the stable and convective layers. A common example is the penetration of thermals from the atmospheric convective boundary layer into the potential temperature inversion capping the mixed layer.
See entrainment zone.