Introducing lower boundary conditions perturbations in a convection-permitting ensemble system: sensitivity to soil moisture perturbation

The aim of this study is to assess the behavior of the high-resolution COSMO model, having convection explicitly solved, to different soil moisture initializations. This work is devoted to understand if and how the model is sensitive to the initial condition of the soil water content. Four different case studies, representing four different meteorological regimes, have been selected for such a purpose using different soil moisture fields prepared ad hoc. Results confirm that the model is very sensitive to the perturbation of the initial conditions of the soil water content, showing a significant spread increase in main prognostic variables, near the soil as well as upper in the atmosphere. These results suggest that an ensemble system, based on a high-resolution convection-permitting model, could benefit in terms of spread increase if a perturbation of the initial conditions of the soil moisture would be added to the classic perturbation of the atmosphere. For an evaluation of the performances of this kind of ensemble system, a comparison with observations should be performed.