Sensitivity of some African heavy rainfall events to microphysics and planetary boundary layer schemes: Impacts on localised storms

Abstract

High-resolution numerical weather prediction (NWP) simulations of heavy rainfall events are known to be strongly sensitive to the choice of the sub-grid scale parameterisation schemes. In the African continent, studies on such a choice at the convective-resolving scales are not numerous. By exploiting a state-of-the-art NWP model, the Weather Research and Forecasting (WRF) model, the sensitivity of the simulation of three heavy rainfall events in Sub-Saharan Africa to the microphysical (MP) and planetary boundary layer (PBL) schemes is studied. Validating the numerical outputs against rainfall satellite estimates, ground-based weather stations, radiosonde profiles and satellite-derived cloud-top temperature maps with an object-based tool, the best-performing setup is identified. In terms of heavy rainfall forecast location, it is found that the PBL scheme has a greater impact than the MP, which is shown to control the cloud-top temperature simulation. Among the schemes considered, the best performances are achieved with a six-class single-moment microphysical scheme and a non-local planetary boundary layer scheme which properly includes the vertical mixing by the large eddies in the atmosphere.