Interactions between simulated supercell thunderstorms and dry boundary layer convection

Surface-based deep convection is generally rooted in a convective boundary layer with inherent horizontal heterogeneities in vertical velocity, wind shear, temperature, and moisture due to the presence of convective cells, rolls, or thermals. However, an overwhelming majority of numerical simulations of deep convection, including supercell thunderstorms, have neglected such features in favor of a simplified horizontally homogeneous environment. To investigate the importance of such effects on supercell evolution, the numerical model CM1 (equipped with radiation and soil parameterizations) is used to initiate deep moist convection in an environment characterized by a convective boundary layer and adequate shear to support supercell thunderstorms.

Simulations of supercell thunderstorms in a convective boundary layer show that vertical velocity and vorticity, particularly along the gust front, may be sensitive to horizontal heterogeneities in the environment. Such effects and their variations relative to the type and orientation of boundary layer convection are examined. Furthermore, shading from the anvil cloud is found to suppress boundary layer convection in the inflow region. Thus, the importance of boundary layer convection on supercell evolution may vary based on the direction of anvil-level winds relative to storm inflow.