Sensitivity of MCS Outflow Characteristics to Low-Level Stability and Shear

Mesoscale convective systems (MCSs) can cause a number of severe hazards from severe winds to extreme rainfall. Studies have indicated that MCSs can be maintained by cold pools, gravity waves, and various types of bores. The interaction of the MCS outflow with the stability and shear of the nocturnal environment plays a key role in the resulting MCS organization and propagation. Further, analysis of soundings collected during the Plains Elevated Convection at Night (PECAN) field campaign in the US Great Plains region indicates substantial variability in the stability and shear in the nocturnal boundary layer between observed pre-convective MCS environments. The goals of this work are to document the impacts that low level environmental stability and shear can have on the organization, propagation, and maintenance of simulated MCSs, and to gain insight into potential mechanisms for the support of back-building convection, in a variety of boundary layer environments.

In this work, a series of idealized simulations using Cloud Model 1 (CM1) will be used to explore the sensitivity of MCS propagation/maintenance mechanisms to changes in shear and stability. A control simulation will be initialized with a base state sounding that has low level wind and thermodynamic characteristics representative of MCS environments with evidence of bore/gravity wave maintenance observed during PECAN. Experimental simulations will vary wind shear and stability in order to understand the role they play in the mode of propagation (e.g. density current/gravity wave/bore/intrusion) and the resulting MCS organization. Particular focus will be given to how stability may impact the processes that support back-building convection.