| The relations between the duration, intensity, and helical structure of supercells and their environments are studied by analyzing simulated storms, and by simulating parallel-plate convection in a background mean shear.;To test the effects of environmental shear on convective storms, we analyze the energy budget of two simulated supercells. The horizontal components of the perturbation flow are decomposed to analyze the energy budget of rotational and divergent flows. The results indicate that the shearing environment both enhances and suppresses storm energetics in each case.;To study the helicity, we simulate parallel-plate convection with various type of mean shear by using a direct numerical model. The results indicate that the normalized three-dimensional nonlinear energy transfer among scales is inversely correlated with the squared relative helicity of the flow for cases with the same Rayleigh number.;The buoyancy-forced convective elements in parallel-plate convection with a curved mean shear are shown to be more likely to be helical than are those with other types of mean shear. In the supercell simulations, buoyant generation is the dominant source of the perturbation helicity for the case with unidirectional shear, while mean-eddy exchange dominates for the case with a curved hodograph.;It is concluded that the net energy exchanges between strongly sheared environment and supercell storms allows development of rotation and helical convection, but does not clearly enhance the convection. Helical convection is shown to be related with small nonlinear energy transfer. This result is consistent with the hypothesis that helicity helps to maintain a favorable structure for storm convection. |
