Influence of vertical wind shear on organisation and decametric-scale turbulence in convective clouds using large-eddy simulations.

This work describes the study of the influence of vertical wind shear (hereafter "shear") on deep convective clouds. Using a set of high-resolution Large-Eddy Simulations (LES) produced by the research model Meso-NH with varying shear, tendencies in the relationship between shear magnitude and the organisation and intensity of the storms are drawn. Increasing shear is associated with higher precipitations, stronger ascent in the updraft, and more intense cold pools under the convective cells. When the shear becomes strong enough, the convective cells evolve into supercells, drastically changing the regime of the event and highlighting a non-linearity in the behaviour of convective systems. Turbulent quantities are affected, with higher subgrid and resolved turbulent kinetic energy (TKE) for higher intensity storms. Moreover, the upwind TKE is higher than the downwind TKE, although the ratio for all simulations is not affected. Using four different indicators of organisation, a clear trend towards increasing organisation is diagnosed, with the supercell regime diverging from the other simulations. Vertical wind shear, via its effect on the organisation of convective cells, significantly alters the effect of convective storms, and should be taken into account by parametrization schemes.