The impact of secondary ice production on the dynamics of extratropical cyclones

Clouds strongly affect the dynamics of extratropical cyclones and large-scale predictability through their microphysical and radiative effects. However, the representation of cloud microphysical and radiative processes remains uncertain in current weather and climate models, with key processes such as Secondary Ice Production (SIP) being simplified or neglected. SIP processes, such as rime splintering, ice-ice collisional breakup, and raindrop fragmentation, can increase ice number concentrations by several orders of magnitude. The enhanced ice production can modify the latent and radiative heating of clouds, thereby affecting the dynamics of extratropical cyclones. However, the impact of SIP processes on the dynamics of extratropical cyclones has not yet been quantitatively assessed.

Here we investigate the impact of SIP processes on the cloud microphysics and dynamics of extratropical cyclones by performing hindcast simulations with and without SIP processes using the ICOsahedral Nonhydrostatic (ICON) model. We focus on cyclones observed during the North Atlantic Waveguide and Downstream impact EXperiment (NAWDEX) field campaign. This enables us to evaluate the modeled microphysical and radiative properties of clouds within cyclones against observations. In addition, we apply the potential vorticity error growth framework to investigate how SIP-induced changes in cloud latent and radiative heating influence the dynamics of cyclones and the circulation near the tropopause. Our results can highlight the implications of improved cloud-ice microphysics for model prediction of extratropical cyclones.