Comparison study of heterogeneous ice nucleation parameterizations in a parcel model framework

Intercomparisons between three heterogeneous ice nucleation parameterizations that link aerosol type and number to ice crystal concentration were conducted. Results indicate large differences in the prediction of ice formation in modestly supercooled clouds and in the susceptibility of cirrus to heterogeneous ice nucleation for the same assumed aerosol distribution.

Only one parameterization has an observational constraint that limits the maximum ice crystal number concentrations to be a fraction of the total number concentrations of potential ice-nucleating particles (typically, all insoluble particles larger than about 0.1 μm). The constrained parameterization compares well with most ice nucleation measurements. The nonconstrained parameterizations are capable of predicting several orders of magnitude higher ice crystal concentrations than the constrained parameterization for the same parcel-forcing conditions.