Impacts of secondary ice production on the microphysics and dynamics of deep convective clouds in different environments

This study numerically investigates the impact of secondary ice production (SIP) on cloud microphysical and diabatic properties in continental and marine deep convective clouds (DCCs). Four cases are simulated using the Icosahedral Nonhydrostatic (ICON) model with a 2-moment cloud microphysics scheme at 1.6 km horizontal grid spacing. ICON forms secondary ice via rime splintering, fragmentation during raindrop freezing (RDF), ice-ice collision, and sublimation. A more detailed RDF scheme (Phillips et al., 2018, PHIL18) is implemented and compared to the existing simpler scheme (Sullivan et al., 2018, SULL18). In the simulated DCCs, SIP processes reproduce observed ice number concentrations, with PHIL18 yielding closer agreement with observations than SULL18. SIP enhances ice numbers by 10–103, decreasing (increasing) supercooled-liquid (ice) mass by 10 %–30 %, leading to sustained upper-level glaciation. Including SIP increases surface precipitation by 4 % in marine DCCs, with no significant change in continental DCCs. SIP enhances longwave absorption in the mixed-phase region and increases (20 % in continental and 40 % in marine DCCs) cloud radiative heating. SIP intensifies latent heating by up to 20 %, reaching 20–40 K d−1 in continental and 80 K d−1 in marine DCCs, from increased depositional growth of ice particles. This enhanced diabatic heating increases buoyancy in the stratiform regions, leading to a 10 % rise in stratiform ascent. In contrast, in convective regions, SIP increases condensate loading, which suppresses buoyancy, leading to similarly weaker convective ascent. These findings highlight the pivotal role of SIP in shaping the microphysical structure and dynamical behavior of deep convection, highlighting the need for its accurate representation in numerical models.