A nudging scheme to assimilate brightness temperature in a meteorological model: impact on African mesoscale convective systems representation

The study presents the implementation of a nudging procedure in a mesoscale meteorological model, and its evaluation in improving the representation of mesoscale convective systems in the region of West Africa. The generation and development of convection are related to processes with different spatial scales, making it often difficult for meteorological models to reproduce their dynamics. The assimilation approach is based on the continuous assimilation of METEOSAT infrared brightness temperatures within the model in order to trigger convection, where observations show the presence of large convective systems. The nudging also inhibits convection, when the model reproduces unrealistic convective precipitation and coherently modifies the dynamical fields. Model sensitivity to the nudging scheme has been tested to evaluate the role of the forcing term. The nudging improves the geographical distribution and time evolution of mesoscale convective systems reproduced by the model; the impact of assimilation is positive up to 13 h after the end of the nudging period. It is also shown that the nudging improves the simulated amount and spatial distribution of precipitation. Finally, the assimilation is performed throughout the entire simulation, showing how the proposed approach can be used to improve meteorological analyses in terms ofconvectiveactivityandrainfall.