High-resolution Radar Rainfall Assimilation: Exploratory Studies with Latent Heat Nudging

Precipitation is certainly one of the most relevant parameters in forecasting the weather, particularly in numerical weather prediction (NWP). Yet, while general NWP has witnessed considerable progress in recent years, quantitative precipitation forecasting (QPF) has shown little to no improvement, especially for the convection-dominated warm season. Reasons for the low performance include model deficiencies, insufficient resolution, and the lack of a properly defined initial model state, particularly related to moisture. Next-generation operational NWP systems will run with grid spacings of around 1 km to circumvent the parametrisation of convection. Such model resolution demands new types of high-resolution observations for initialisation. Doppler radars are able to provide information on precipitation-related phenomena with sufficient spatio-temporal resolution for this purpose. In order to meet the tight time constraints in short-range NWP, very efficient radar assimilation methods will be essential.