Initiation of deep convection by boundary-layer convergence lines during TRACER: preliminary insights from idealized modeling and Lagrangian diagnostics

Description

Boundary-layer convergence lines (CLs) can promote deep-convection initiation by generating stronger, more coherent updrafts than ambient turbulent flows. To study these processes in isolation, we perform large-eddy simulations in a simplified coastal configuration forced using initial and boundary conditions obtained from the TRACER campaign data. Convergence arises from differential heating and/or cold pools, triggering clouds whose growth is studied using a Lagrangian particle model. Preliminary results show that CL-forced clouds develop stronger subcloud updrafts, entrain less air, and sustain buoyancy more effectively than clouds forming outside convergence zones. Updraft width and velocity appear critical in driving this reduced entrainment, while environmental factors like stability and surface fluxes modulate cloud evolution. Future work will extend these experiments, for example quantifying the role of pre-conditioning in facilitating the shallow-to-deep transition. Ultimately, these idealized simulations provide mechanistic insights that can help refine convective parameterizations in weather and climate models.