A numerical investigation of the dependence of the circulation of low-level mesocyclones on the characteristics of the outflow and the environment

Rotunno and Klemp (1985) analyzed the growth of circulation about a material circuit that converged upon the low-level mesocyclone of a simulated supercell. They showed that the positive circulation acquired by the material circuit was solely the result of baroclinic vorticity generation experienced by the parcels comprising the circuit as they passed through the horizontal buoyancy gradient associated with the forward-flank precipitation region. The environment actually contributed negative circulation about the circuit. Since Rotunno and Klemp's analysis, only a paucity of subsequent studies have analyzed the development of low-level circulation using a similar methodology; thus, the generality of the evolution of circulation about the material circuits in the simulation of Rotunno and Klemp remains unclear. To what extent does the development of circulation at low levels depend on the length and curvature of the environmental hodograph, the properties of the sounding, and processes that affect cold pool strength (e.g., microphysics)? We will present some preliminary results from a carefully controlled numerical simulation study designed to tackle these questions.