Simulating supercell thunderstorms in a horizontally heterogeneous convective boundary layer

The vast majority of numerical modeling studies investigating supercell thunderstorms have been initialized with a horizontally homogeneous base state lacking a true boundary layer. Although most idealized supercell simulations have an implied boundary layer in their initial soundings (e.g., a layer at the bottom of the sounding with nearly well-mixed potential temperature and water vapor mixing ratio), the lack of surface fluxes and, in many cases, horizontal homogeneity and/or insufficient resolution, have precluded the development of a realistic convective boundary layer characterized by cells, rolls, and thermals. However, such horizontal heterogeneities in vertical velocity, wind shear, and thermodynamic characteristics of the convective boundary layer are believed to have important influences on storm development and maintenance.

In this preliminary study, supercell thunderstorms are simulated in an environment having a more realistic convective boundary layer. The Bryan Cloud Model (CM1), equipped with radiation and soil parameterizations, is used to develop a convective boundary layer and initiate deep moist convection in an environment with adequate shear to support supercells. The effects of local variations in vertical velocity and moisture associated with boundary layer convection on storm evolution are examined.