The impacts of secondary ice production on the microphysics and dynamics of mid-latitude cold season convection

Abstract. This study examines the impact of inclusion of secondary ice production (SIP) parameterizations on the cloud microphysics and dynamics in numerical weather prediction (NWP) simulations under mid-latitude winter conditions. Hindcast mesoscale model simulations were performed for two flights from the 2019 In-Cloud ICing and Large-drop Experiment (ICICLE) field campaign. The simulations used a horizontal grid spacing of 250 meters and employed a detailed triple-moment bulk microphysics scheme capable of predicting the liquid fraction of hydrometeors. SIP processes, including the Hallett-Mossop (HM), fragmentation of freezing drops (FFD) and fragmentation due to ice-ice collisional breakup (CB), are parameterized in this study. The NWP simulation results are compared with observational data collected during the ICICLE campaign. Sensitivity tests were conducted to highlight the importance of better quantifying SIP production rate in the NWP models. The findings indicate that SIP significantly enhances the simulated cloud ice number concentration and ice water content, particularly under strong convective conditions during winter. Additionally, the results reveal that the simulations are highly sensitive to the parameterization of HM, FFD and CB processes due to the interaction between these SIP mechanisms. High ice water content (HIWC) production is closely associated with SIP in strong convective conditions, whereas in stratiform conditions, HIWC can occur without a significant impact from SIP.