Ice Initiation by Aerosol Particles: Measured and Predicted Ice Nuclei Concentrations versus Measured Ice Crystal Concentrations in an Orographic Wave Cloud

摘要

The initiation of ice in an isolated orographic wave cloud was compared with expectations based on ice\udnucleating aerosol concentrations and with predictions from new ice nucleation parameterizations applied in\uda cloud parcel model. Measurements of ice crystal number concentrations were found to be in good agreement\udboth with measured number concentrations of ice nuclei feeding the clouds and with ice nuclei number\udconcentrations determined from the residual nuclei of cloud particles collected by a counterflow virtual\udimpactor. Using lognormal distributions fitted to measured aerosol size distributions and measured aerosol\udchemical compositions, ice nuclei and ice crystal concentrations in the wave cloud were reasonably well\udpredicted in a 1Dparcel model framework. Two different empirical parameterizations were used in the parcel\udmodel: a parameterization based on aerosol chemical type and surface area and a parameterization that links\udice nuclei number concentrations to the number concentrations of particles with diameters larger than\ud0.5 mm. This study shows that aerosol size distribution and composition measurements can be used to constrain\udice initiation by primary nucleation in models. The data and model results also suggest the likelihood\udthat the dust particle mode of the aerosol size distribution controls the number concentrations of the heterogeneous\udice nuclei, at least for the lower temperatures examined in this case.