Impacts of terminal velocity on precipitation prediction and the error representation of terminal velocity in ensemble forecasts

Impacts of terminal velocities (rainwater, snow, and hail) on precipitation and the representation of terminal velocity uncertainty in ensemble forecasts were discussed in several idealized scenarios differing in intercept parameters and environmental soundings. In this idealized case, the precipitation maximum and cold pool were sensitive to the rainwater terminal velocity, while the precipitation coverage was sensitive to terminal velocities of ice‐species. Although precipitation maximum approximately increased with terminal velocity, pronouncedly large terminal velocity may form a cold pool too weak for precipitation system development. The main finding for ensemble forecasts is that allowing for terminal velocity uncertainty in ensemble forecasts could benefit the precipitation forecast skill; using perturbations based on the terminal velocity bias of each species improved the forecast skill in more scenarios than using the same perturbation for all species. The microphysics parameterization is a big source of the uncertainty of convective prediction, which includes the estimates of intercept parameter, ice density, and terminal velocity. In the present of the terminal velocity bias, taking into account this bias (Ens_diag, dot lines) improves the reliability of the precipitation ensemble forecasts using the one‐moment Lin scheme; a two‐moment microphysics scheme serves as the truth. The present work highlights the necessity to consider the terminal velocity bias in ensemble forecasts.