Examination of Convection Initiation using MPEX Soundings and Convection-Permitting Simulations

In this study we use both field observations from the Mesoscale Predictability Experiment (MPEX) and convection-permitting numerical simulations to examine evolution of thermodynamic conditions influencing convection initiation (CI). Recent work has illustrated several advantages of using the minimum buoyancy (Bmin) of air parcels from specified source levels as a surrogate for the convective inhibition (CIN). Since Bmin does not depend on there being convective available potential energy (CAPE), assessing thermodynamic destabilization rates with Bmin is more meaningful than with CIN in circumstances where the atmosphere is initially conditionally stable. Another advantage of Bmin lies in the relative ease (compared to CIN) of calculating forcing budgets aimed at attribution of thermodynamic destabilization to specific physical processes, since no vertical integration is required. The primary limitation of analysis using Bmin concerns representativeness issues since only two vertical levels (the parcel origination level and its level of minimum buoyancy) are used in these calculations, compared with CIN which is the vertical integral of negative buoyancy between the parcel source level and its level of free convection (LFC). We address this issue in the current study by comparing modeled soundings with corresponding mobile upsondes (having greater vertical resolutions) in well-simulated MPEX CI cases. We also examine some thermodynamical effects not accounted for in parcel theory (upon which both Bmin and CIN are based), including entrainment of environmental air, on Bmin and associated CI.