The effect of mesoscale heterogeneity on the genesis and structure of mesovortices within quasi-linear convective systems

This study examines the structure and evolution of quasi-linear convective systems (QLCSs) within complex mesoscale environments. Convective outflows and other mesoscale features appear to affect the rotational characteristics and associated dynamics of these systems. Thus, real-data numerical simulations of two QLCS events have been performed to (i) identify and characterize the various ambient mesoscale features that modify the structure and evolution of simulated QLCSs; and then to (ii) determine the nature of interaction of such features with the systems, with an emphasis on the genesis and evolution of low-level mesovortices. Significant low-level mesovortices develop in both simulated QLCSs as a consequence of mechanisms internal to the system - consistent with idealized numerical simulations of mesovortex-bearing QLCSs - and not as an effect of system interaction with external heterogeneity. However, meso-γ-scale (order of 10 km) heterogeneity in the form of a convective outflow boundary is sufficient to affect mesovortex strength, as air parcels populating the vortex region encounter enhanced convergence at the point of QLCS - boundary interaction. Moreover, meso-β-scale (order of 100 km) heterogeneity in the form of interacting air masses provides for along-line variations in the distributions of low- to midlevel vertical wind shear and convective available potential energy. The subsequent impact on updraft strength/ tilt has implications on the vortex stretching experienced by leading-edge mesovortices.