Probing Cirrus Cloud Thinning at a Process Level Using Cloud Chamber Experiments and Numerical Simulations

In this study, we present a series of systematic AIDA cloud chamber experiments investigating the efficiency of cirrus cloud thinning (i.e., the competition between heterogeneous and homogeneous ice nucleation) at temperatures below 230 K. Based on our experimental results, we use a Lagrangian parcel model to simulate cirrus cloud formation and investigate the influence of seeding concentration, updraft velocity and temperatureon the observed total ice crystal concentrations. We find that the ice crystal concentrations are very sensitive to the complex interplay between background aerosol, seeding and updraft velocities, with regimes of successful cirrus thinning, as well as regimes resulting in thicker cirrus (overseeding) being observed.